11 files changed, 284 insertions, 83 deletions

diff --git a/drivers/mmc/mmc_block.c b/drivers/mmc/mmc_block.c
index 9b629856c735..d91fcf7c3178 100644
--- a/drivers/mmc/mmc_block.c
+++ b/drivers/mmc/mmc_block.c
@@ -203,7 +203,6 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
                         brq.data.flags |= MMC_DATA_READ;
                 } else {
                         brq.cmd.opcode = MMC_WRITE_BLOCK;
-                        brq.cmd.flags = MMC_RSP_R1B;
                         brq.data.flags |= MMC_DATA_WRITE;
                         brq.data.blocks = 1;
                 }
diff --git a/drivers/mmc/wbsd.c b/drivers/mmc/wbsd.c
index 942668e93a74..4ff67e7363d9 100644
--- a/drivers/mmc/wbsd.c
+++ b/drivers/mmc/wbsd.c
@@ -201,7 +201,7 @@ static void wbsd_reset(struct wbsd_host* host)
 {
         u8 setup;
 
-        printk(KERN_ERR DRIVER_NAME ": Resetting chip\n");
+        printk(KERN_ERR "%s: Resetting chip\n", mmc_hostname(host->mmc));
 
         /*
          * Soft reset of chip (SD/MMC part).
@@ -880,8 +880,9 @@ static void wbsd_finish_data(struct wbsd_host* host, struct mmc_data* data)
                  */
                 if (count)
                 {
-                        printk(KERN_ERR DRIVER_NAME ": Incomplete DMA "
-                                "transfer. %d bytes left.\n", count);
+                        printk(KERN_ERR "%s: Incomplete DMA transfer. "
+                                "%d bytes left.\n",
+                                mmc_hostname(host->mmc), count);
 
                         data->error = MMC_ERR_FAILED;
                 }
@@ -1169,8 +1170,8 @@ static void wbsd_tasklet_card(unsigned long param)
 
                 if (host->mrq)
                 {
-                        printk(KERN_ERR DRIVER_NAME
-                                ": Card removed during transfer!\n");
+                        printk(KERN_ERR "%s: Card removed during transfer!\n",
+                                mmc_hostname(host->mmc));
                         wbsd_reset(host);
 
                         host->mrq->cmd->error = MMC_ERR_FAILED;
@@ -1852,9 +1853,9 @@ static int __devinit wbsd_init(struct device* dev, int base, int irq, int dma,
         /*
          * See if chip needs to be configured.
          */
-        if (pnp && (host->config != 0))
+        if (pnp)
         {
-                if (!wbsd_chip_validate(host))
+                if ((host->config != 0) && !wbsd_chip_validate(host))
                 {
                         printk(KERN_WARNING DRIVER_NAME
                                 ": PnP active but chip not configured! "
diff --git a/drivers/scsi/ahci.c b/drivers/scsi/ahci.c
index e2a5657d5fdb..4612312c0c2d 100644
--- a/drivers/scsi/ahci.c
+++ b/drivers/scsi/ahci.c
@@ -307,14 +307,22 @@ static int ahci_port_start(struct ata_port *ap)
         void __iomem *port_mmio = ahci_port_base(mmio, ap->port_no);
         void *mem;
         dma_addr_t mem_dma;
+        int rc;
 
         pp = kmalloc(sizeof(*pp), GFP_KERNEL);
         if (!pp)
                 return -ENOMEM;
         memset(pp, 0, sizeof(*pp));
 
+        rc = ata_pad_alloc(ap, dev);
+        if (rc) {
+                kfree(pp);
+                return rc;
+        }
+
         mem = dma_alloc_coherent(dev, AHCI_PORT_PRIV_DMA_SZ, &mem_dma, GFP_KERNEL);
         if (!mem) {
+                ata_pad_free(ap, dev);
                 kfree(pp);
                 return -ENOMEM;
         }
@@ -390,6 +398,7 @@ static void ahci_port_stop(struct ata_port *ap)
         ap->private_data = NULL;
         dma_free_coherent(dev, AHCI_PORT_PRIV_DMA_SZ,
                           pp->cmd_slot, pp->cmd_slot_dma);
+        ata_pad_free(ap, dev);
         kfree(pp);
 }
 
@@ -468,23 +477,23 @@ static void ahci_tf_read(struct ata_port *ap, struct ata_taskfile *tf)
 static void ahci_fill_sg(struct ata_queued_cmd *qc)
 {
         struct ahci_port_priv *pp = qc->ap->private_data;
-        unsigned int i;
+        struct scatterlist *sg;
+        struct ahci_sg *ahci_sg;
 
         VPRINTK("ENTER\n");
 
         /*
          * Next, the S/G list.
          */
-        for (i = 0; i < qc->n_elem; i++) {
-                u32 sg_len;
-                dma_addr_t addr;
-
-                addr = sg_dma_address(&qc->sg[i]);
-                sg_len = sg_dma_len(&qc->sg[i]);
-
-                pp->cmd_tbl_sg[i].addr = cpu_to_le32(addr & 0xffffffff);
-                pp->cmd_tbl_sg[i].addr_hi = cpu_to_le32((addr >> 16) >> 16);
-                pp->cmd_tbl_sg[i].flags_size = cpu_to_le32(sg_len - 1);
+        ahci_sg = pp->cmd_tbl_sg;
+        ata_for_each_sg(sg, qc) {
+                dma_addr_t addr = sg_dma_address(sg);
+                u32 sg_len = sg_dma_len(sg);
+
+                ahci_sg->addr = cpu_to_le32(addr & 0xffffffff);
+                ahci_sg->addr_hi = cpu_to_le32((addr >> 16) >> 16);
+                ahci_sg->flags_size = cpu_to_le32(sg_len - 1);
+                ahci_sg++;
         }
 }
 
diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index ff18fa7044c5..e1346cddd37f 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -2390,8 +2390,9 @@ static void ata_dev_init_params(struct ata_port *ap, struct ata_device *dev)
 static void ata_sg_clean(struct ata_queued_cmd *qc)
 {
         struct ata_port *ap = qc->ap;
-        struct scatterlist *sg = qc->sg;
+        struct scatterlist *sg = qc->__sg;
         int dir = qc->dma_dir;
+        void *pad_buf = NULL;
 
         assert(qc->flags & ATA_QCFLAG_DMAMAP);
         assert(sg != NULL);
@@ -2401,14 +2402,35 @@ static void ata_sg_clean(struct ata_queued_cmd *qc)
 
         DPRINTK("unmapping %u sg elements\n", qc->n_elem);
 
-        if (qc->flags & ATA_QCFLAG_SG)
+        /* if we padded the buffer out to 32-bit bound, and data
+         * xfer direction is from-device, we must copy from the
+         * pad buffer back into the supplied buffer
+         */
+        if (qc->pad_len && !(qc->tf.flags & ATA_TFLAG_WRITE))
+                pad_buf = ap->pad + (qc->tag * ATA_DMA_PAD_SZ);
+
+        if (qc->flags & ATA_QCFLAG_SG) {
                 dma_unmap_sg(ap->host_set->dev, sg, qc->n_elem, dir);
-        else
+                /* restore last sg */
+                sg[qc->orig_n_elem - 1].length += qc->pad_len;
+                if (pad_buf) {
+                        struct scatterlist *psg = &qc->pad_sgent;
+                        void *addr = kmap_atomic(psg->page, KM_IRQ0);
+                        memcpy(addr + psg->offset, pad_buf, qc->pad_len);
+                        kunmap_atomic(psg->page, KM_IRQ0);
+                }
+        } else {
                 dma_unmap_single(ap->host_set->dev, sg_dma_address(&sg[0]),
                                  sg_dma_len(&sg[0]), dir);
+                /* restore sg */
+                sg->length += qc->pad_len;
+                if (pad_buf)
+                        memcpy(qc->buf_virt + sg->length - qc->pad_len,
+                               pad_buf, qc->pad_len);
+        }
 
         qc->flags &= ~ATA_QCFLAG_DMAMAP;
-        qc->sg = NULL;
+        qc->__sg = NULL;
 }
 
 /**
@@ -2424,15 +2446,15 @@ static void ata_sg_clean(struct ata_queued_cmd *qc)
  */
 static void ata_fill_sg(struct ata_queued_cmd *qc)
 {
-        struct scatterlist *sg = qc->sg;
         struct ata_port *ap = qc->ap;
-        unsigned int idx, nelem;
+        struct scatterlist *sg;
+        unsigned int idx;
 
-        assert(sg != NULL);
+        assert(qc->__sg != NULL);
         assert(qc->n_elem > 0);
 
         idx = 0;
-        for (nelem = qc->n_elem; nelem; nelem--,sg++) {
+        ata_for_each_sg(sg, qc) {
                 u32 addr, offset;
                 u32 sg_len, len;
 
@@ -2518,12 +2540,18 @@ void ata_qc_prep(struct ata_queued_cmd *qc)
 
 void ata_sg_init_one(struct ata_queued_cmd *qc, void *buf, unsigned int buflen)
 {
+        struct scatterlist *sg;
+
         qc->flags |= ATA_QCFLAG_SINGLE;
 
-        qc->sg = &qc->sgent;
+        memset(&qc->sgent, 0, sizeof(qc->sgent));
+        qc->__sg = &qc->sgent;
         qc->n_elem = 1;
+        qc->orig_n_elem = 1;
         qc->buf_virt = buf;
-        sg_init_one(qc->sg, buf, buflen);
+
+        sg = qc->__sg;
+        sg_init_one(sg, buf, buflen);
 }
 
 /**
@@ -2544,8 +2572,9 @@ void ata_sg_init(struct ata_queued_cmd *qc, struct scatterlist *sg,
                  unsigned int n_elem)
 {
         qc->flags |= ATA_QCFLAG_SG;
-        qc->sg = sg;
+        qc->__sg = sg;
         qc->n_elem = n_elem;
+        qc->orig_n_elem = n_elem;
 }
 
 /**
@@ -2565,9 +2594,32 @@ static int ata_sg_setup_one(struct ata_queued_cmd *qc)
 {
         struct ata_port *ap = qc->ap;
         int dir = qc->dma_dir;
-        struct scatterlist *sg = qc->sg;
+        struct scatterlist *sg = qc->__sg;
         dma_addr_t dma_address;
 
+        /* we must lengthen transfers to end on a 32-bit boundary */
+        qc->pad_len = sg->length & 3;
+        if (qc->pad_len) {
+                void *pad_buf = ap->pad + (qc->tag * ATA_DMA_PAD_SZ);
+                struct scatterlist *psg = &qc->pad_sgent;
+
+                assert(qc->dev->class == ATA_DEV_ATAPI);
+
+                memset(pad_buf, 0, ATA_DMA_PAD_SZ);
+
+                if (qc->tf.flags & ATA_TFLAG_WRITE)
+                        memcpy(pad_buf, qc->buf_virt + sg->length - qc->pad_len,
+                               qc->pad_len);
+
+                sg_dma_address(psg) = ap->pad_dma + (qc->tag * ATA_DMA_PAD_SZ);
+                sg_dma_len(psg) = ATA_DMA_PAD_SZ;
+                /* trim sg */
+                sg->length -= qc->pad_len;
+
+                DPRINTK("padding done, sg->length=%u pad_len=%u\n",
+                        sg->length, qc->pad_len);
+        }
+
         dma_address = dma_map_single(ap->host_set->dev, qc->buf_virt,
                                      sg->length, dir);
         if (dma_mapping_error(dma_address))
@@ -2599,12 +2651,47 @@ static int ata_sg_setup_one(struct ata_queued_cmd *qc)
 static int ata_sg_setup(struct ata_queued_cmd *qc)
 {
         struct ata_port *ap = qc->ap;
-        struct scatterlist *sg = qc->sg;
+        struct scatterlist *sg = qc->__sg;
+        struct scatterlist *lsg = &sg[qc->n_elem - 1];
         int n_elem, dir;
 
         VPRINTK("ENTER, ata%u\n", ap->id);
         assert(qc->flags & ATA_QCFLAG_SG);
 
+        /* we must lengthen transfers to end on a 32-bit boundary */
+        qc->pad_len = lsg->length & 3;
+        if (qc->pad_len) {
+                void *pad_buf = ap->pad + (qc->tag * ATA_DMA_PAD_SZ);
+                struct scatterlist *psg = &qc->pad_sgent;
+                unsigned int offset;
+
+                assert(qc->dev->class == ATA_DEV_ATAPI);
+
+                memset(pad_buf, 0, ATA_DMA_PAD_SZ);
+
+                /*
+                 * psg->page/offset are used to copy to-be-written
+                 * data in this function or read data in ata_sg_clean.
+                 */
+                offset = lsg->offset + lsg->length - qc->pad_len;
+                psg->page = nth_page(lsg->page, offset >> PAGE_SHIFT);
+                psg->offset = offset_in_page(offset);
+
+                if (qc->tf.flags & ATA_TFLAG_WRITE) {
+                        void *addr = kmap_atomic(psg->page, KM_IRQ0);
+                        memcpy(pad_buf, addr + psg->offset, qc->pad_len);
+                        kunmap_atomic(psg->page, KM_IRQ0);
+                }
+
+                sg_dma_address(psg) = ap->pad_dma + (qc->tag * ATA_DMA_PAD_SZ);
+                sg_dma_len(psg) = ATA_DMA_PAD_SZ;
+                /* trim last sg */
+                lsg->length -= qc->pad_len;
+
+                DPRINTK("padding done, sg[%d].length=%u pad_len=%u\n",
+                        qc->n_elem - 1, lsg->length, qc->pad_len);
+        }
+
         dir = qc->dma_dir;
         n_elem = dma_map_sg(ap->host_set->dev, sg, qc->n_elem, dir);
         if (n_elem < 1)
@@ -2880,7 +2967,7 @@ static void ata_data_xfer(struct ata_port *ap, unsigned char *buf,
 static void ata_pio_sector(struct ata_queued_cmd *qc)
 {
         int do_write = (qc->tf.flags & ATA_TFLAG_WRITE);
-        struct scatterlist *sg = qc->sg;
+        struct scatterlist *sg = qc->__sg;
         struct ata_port *ap = qc->ap;
         struct page *page;
         unsigned int offset;
@@ -2930,7 +3017,7 @@ static void ata_pio_sector(struct ata_queued_cmd *qc)
 static void __atapi_pio_bytes(struct ata_queued_cmd *qc, unsigned int bytes)
 {
         int do_write = (qc->tf.flags & ATA_TFLAG_WRITE);
-        struct scatterlist *sg = qc->sg;
+        struct scatterlist *sg = qc->__sg;
         struct ata_port *ap = qc->ap;
         struct page *page;
         unsigned char *buf;
@@ -2963,7 +3050,7 @@ next_sg:
                 return;
         }
 
-        sg = &qc->sg[qc->cursg];
+        sg = &qc->__sg[qc->cursg];
 
         page = sg->page;
         offset = sg->offset + qc->cursg_ofs;
@@ -3320,7 +3407,7 @@ struct ata_queued_cmd *ata_qc_new_init(struct ata_port *ap,
 
         qc = ata_qc_new(ap);
         if (qc) {
-                qc->sg = NULL;
+                qc->__sg = NULL;
                 qc->flags = 0;
                 qc->scsicmd = NULL;
                 qc->ap = ap;
@@ -4004,11 +4091,18 @@ err_out:
 int ata_port_start (struct ata_port *ap)
 {
         struct device *dev = ap->host_set->dev;
+        int rc;
 
         ap->prd = dma_alloc_coherent(dev, ATA_PRD_TBL_SZ, &ap->prd_dma, GFP_KERNEL);
         if (!ap->prd)
                 return -ENOMEM;
 
+        rc = ata_pad_alloc(ap, dev);
+        if (rc) {
+                dma_free_coherent(dev, ATA_PRD_TBL_SZ, ap->prd, ap->prd_dma);
+                return rc;
+        }
+
         DPRINTK("prd alloc, virt %p, dma %llx\n", ap->prd, (unsigned long long) ap->prd_dma);
 
         return 0;
@@ -4032,6 +4126,7 @@ void ata_port_stop (struct ata_port *ap)
         struct device *dev = ap->host_set->dev;
 
         dma_free_coherent(dev, ATA_PRD_TBL_SZ, ap->prd, ap->prd_dma);
+        ata_pad_free(ap, dev);
 }
 
 void ata_host_stop (struct ata_host_set *host_set)
diff --git a/drivers/scsi/libata-scsi.c b/drivers/scsi/libata-scsi.c
index 248baae96486..eb604b0a8990 100644
--- a/drivers/scsi/libata-scsi.c
+++ b/drivers/scsi/libata-scsi.c
@@ -355,10 +355,10 @@ struct ata_queued_cmd *ata_scsi_qc_new(struct ata_port *ap,
                 qc->scsidone = done;
 
                 if (cmd->use_sg) {
-                        qc->sg = (struct scatterlist *) cmd->request_buffer;
+                        qc->__sg = (struct scatterlist *) cmd->request_buffer;
                         qc->n_elem = cmd->use_sg;
                 } else {
-                        qc->sg = &qc->sgent;
+                        qc->__sg = &qc->sgent;
                         qc->n_elem = 1;
                 }
         } else {
@@ -702,6 +702,16 @@ int ata_scsi_slave_config(struct scsi_device *sdev)
                          */
                         blk_queue_max_sectors(sdev->request_queue, 2048);
                 }
+
+                /*
+                 * SATA DMA transfers must be multiples of 4 byte, so
+                 * we need to pad ATAPI transfers using an extra sg.
+                 * Decrement max hw segments accordingly.
+                 */
+                if (dev->class == ATA_DEV_ATAPI) {
+                        request_queue_t *q = sdev->request_queue;
+                        blk_queue_max_hw_segments(q, q->max_hw_segments - 1);
+                }
         }
 
         return 0;       /* scsi layer doesn't check return value, sigh */
diff --git a/drivers/scsi/pdc_adma.c b/drivers/scsi/pdc_adma.c
index 665017eda8a6..a50588c60fab 100644
--- a/drivers/scsi/pdc_adma.c
+++ b/drivers/scsi/pdc_adma.c
@@ -293,14 +293,14 @@ static void adma_eng_timeout(struct ata_port *ap)
 
 static int adma_fill_sg(struct ata_queued_cmd *qc)
 {
-        struct scatterlist *sg = qc->sg;
+        struct scatterlist *sg;
         struct ata_port *ap = qc->ap;
         struct adma_port_priv *pp = ap->private_data;
         u8  *buf = pp->pkt;
-        int nelem, i = (2 + buf[3]) * 8;
+        int i = (2 + buf[3]) * 8;
         u8 pFLAGS = pORD | ((qc->tf.flags & ATA_TFLAG_WRITE) ? pDIRO : 0);
 
-        for (nelem = 0; nelem < qc->n_elem; nelem++,sg++) {
+        ata_for_each_sg(sg, qc) {
                 u32 addr;
                 u32 len;
 
@@ -312,7 +312,7 @@ static int adma_fill_sg(struct ata_queued_cmd *qc)
                 *(__le32 *)(buf + i) = cpu_to_le32(len);
                 i += 4;
 
-                if ((nelem + 1) == qc->n_elem)
+                if (ata_sg_is_last(sg, qc))
                         pFLAGS |= pEND;
                 buf[i++] = pFLAGS;
                 buf[i++] = qc->dev->dma_mode & 0xf;
diff --git a/drivers/scsi/sata_mv.c b/drivers/scsi/sata_mv.c
index 46dbdee79f77..0f469e3dabe2 100644
--- a/drivers/scsi/sata_mv.c
+++ b/drivers/scsi/sata_mv.c
@@ -670,6 +670,11 @@ static void mv_host_stop(struct ata_host_set *host_set)
         ata_host_stop(host_set);
 }
 
+static inline void mv_priv_free(struct mv_port_priv *pp, struct device *dev)
+{
+        dma_free_coherent(dev, MV_PORT_PRIV_DMA_SZ, pp->crpb, pp->crpb_dma);
+}
+
 /**
  *      mv_port_start - Port specific init/start routine.
  *      @ap: ATA channel to manipulate
@@ -687,21 +692,23 @@ static int mv_port_start(struct ata_port *ap)
         void __iomem *port_mmio = mv_ap_base(ap);
         void *mem;
         dma_addr_t mem_dma;
+        int rc = -ENOMEM;
 
         pp = kmalloc(sizeof(*pp), GFP_KERNEL);
-        if (!pp) {
-                return -ENOMEM;
-        }
+        if (!pp)
+                goto err_out;
         memset(pp, 0, sizeof(*pp));
 
         mem = dma_alloc_coherent(dev, MV_PORT_PRIV_DMA_SZ, &mem_dma, 
                                  GFP_KERNEL);
-        if (!mem) {
-                kfree(pp);
-                return -ENOMEM;
-        }
+        if (!mem)
+                goto err_out_pp;
         memset(mem, 0, MV_PORT_PRIV_DMA_SZ);
 
+        rc = ata_pad_alloc(ap, dev);
+        if (rc)
+                goto err_out_priv;
+
         /* First item in chunk of DMA memory: 
          * 32-slot command request table (CRQB), 32 bytes each in size
          */
@@ -746,6 +753,13 @@ static int mv_port_start(struct ata_port *ap)
          */
         ap->private_data = pp;
         return 0;
+
+err_out_priv:
+        mv_priv_free(pp, dev);
+err_out_pp:
+        kfree(pp);
+err_out:
+        return rc;
 }
 
 /**
@@ -768,7 +782,8 @@ static void mv_port_stop(struct ata_port *ap)
         spin_unlock_irqrestore(&ap->host_set->lock, flags);
 
         ap->private_data = NULL;
-        dma_free_coherent(dev, MV_PORT_PRIV_DMA_SZ, pp->crpb, pp->crpb_dma);
+        ata_pad_free(ap, dev);
+        mv_priv_free(pp, dev);
         kfree(pp);
 }
 
@@ -784,23 +799,24 @@ static void mv_port_stop(struct ata_port *ap)
 static void mv_fill_sg(struct ata_queued_cmd *qc)
 {
         struct mv_port_priv *pp = qc->ap->private_data;
-        unsigned int i;
+        unsigned int i = 0;
+        struct scatterlist *sg;
 
-        for (i = 0; i < qc->n_elem; i++) {
+        ata_for_each_sg(sg, qc) {
                 u32 sg_len;
                 dma_addr_t addr;
 
-                addr = sg_dma_address(&qc->sg[i]);
-                sg_len = sg_dma_len(&qc->sg[i]);
+                addr = sg_dma_address(sg);
+                sg_len = sg_dma_len(sg);
 
                 pp->sg_tbl[i].addr = cpu_to_le32(addr & 0xffffffff);
                 pp->sg_tbl[i].addr_hi = cpu_to_le32((addr >> 16) >> 16);
                 assert(0 == (sg_len & ~MV_DMA_BOUNDARY));
                 pp->sg_tbl[i].flags_size = cpu_to_le32(sg_len);
-        }
-        if (0 < qc->n_elem) {
-                pp->sg_tbl[qc->n_elem - 1].flags_size |= 
-                        cpu_to_le32(EPRD_FLAG_END_OF_TBL);
+                if (ata_sg_is_last(sg, qc))
+                        pp->sg_tbl[i].flags_size |= cpu_to_le32(EPRD_FLAG_END_OF_TBL);
+
+                i++;
         }
 }
 
diff --git a/drivers/scsi/sata_qstor.c b/drivers/scsi/sata_qstor.c
index 9938dae782b6..65502c157a54 100644
--- a/drivers/scsi/sata_qstor.c
+++ b/drivers/scsi/sata_qstor.c
@@ -271,16 +271,17 @@ static void qs_scr_write (struct ata_port *ap, unsigned int sc_reg, u32 val)
 
 static void qs_fill_sg(struct ata_queued_cmd *qc)
 {
-        struct scatterlist *sg = qc->sg;
+        struct scatterlist *sg;
         struct ata_port *ap = qc->ap;
         struct qs_port_priv *pp = ap->private_data;
         unsigned int nelem;
         u8 *prd = pp->pkt + QS_CPB_BYTES;
 
-        assert(sg != NULL);
+        assert(qc->__sg != NULL);
         assert(qc->n_elem > 0);
 
-        for (nelem = 0; nelem < qc->n_elem; nelem++,sg++) {
+        nelem = 0;
+        ata_for_each_sg(sg, qc) {
                 u64 addr;
                 u32 len;
 
@@ -294,6 +295,7 @@ static void qs_fill_sg(struct ata_queued_cmd *qc)
 
                 VPRINTK("PRD[%u] = (0x%llX, 0x%X)\n", nelem,
                                         (unsigned long long)addr, len);
+                nelem++;
         }
 }
 
diff --git a/drivers/scsi/sata_sil24.c b/drivers/scsi/sata_sil24.c
index c66548025657..e6c8e89c226f 100644
--- a/drivers/scsi/sata_sil24.c
+++ b/drivers/scsi/sata_sil24.c
@@ -411,15 +411,20 @@ static void sil24_phy_reset(struct ata_port *ap)
 static inline void sil24_fill_sg(struct ata_queued_cmd *qc,
                                  struct sil24_cmd_block *cb)
 {
-        struct scatterlist *sg = qc->sg;
         struct sil24_sge *sge = cb->sge;
-        unsigned i;
+        struct scatterlist *sg;
+        unsigned int idx = 0;
 
-        for (i = 0; i < qc->n_elem; i++, sg++, sge++) {
+        ata_for_each_sg(sg, qc) {
                 sge->addr = cpu_to_le64(sg_dma_address(sg));
                 sge->cnt = cpu_to_le32(sg_dma_len(sg));
-                sge->flags = 0;
-                sge->flags = i < qc->n_elem - 1 ? 0 : cpu_to_le32(SGE_TRM);
+                if (ata_sg_is_last(sg, qc))
+                        sge->flags = cpu_to_le32(SGE_TRM);
+                else
+                        sge->flags = 0;
+
+                sge++;
+                idx++;
         }
 }
 
@@ -630,6 +635,13 @@ static irqreturn_t sil24_interrupt(int irq, void *dev_instance, struct pt_regs *
         return IRQ_RETVAL(handled);
 }
 
+static inline void sil24_cblk_free(struct sil24_port_priv *pp, struct device *dev)
+{
+        const size_t cb_size = sizeof(*pp->cmd_block);
+
+        dma_free_coherent(dev, cb_size, pp->cmd_block, pp->cmd_block_dma);
+}
+
 static int sil24_port_start(struct ata_port *ap)
 {
         struct device *dev = ap->host_set->dev;
@@ -637,36 +649,44 @@ static int sil24_port_start(struct ata_port *ap)
         struct sil24_cmd_block *cb;
         size_t cb_size = sizeof(*cb);
         dma_addr_t cb_dma;
+        int rc = -ENOMEM;
 
-        pp = kmalloc(sizeof(*pp), GFP_KERNEL);
+        pp = kzalloc(sizeof(*pp), GFP_KERNEL);
         if (!pp)
-                return -ENOMEM;
-        memset(pp, 0, sizeof(*pp));
+                goto err_out;
 
         pp->tf.command = ATA_DRDY;
 
         cb = dma_alloc_coherent(dev, cb_size, &cb_dma, GFP_KERNEL);
-        if (!cb) {
-                kfree(pp);
-                return -ENOMEM;
-        }
+        if (!cb)
+                goto err_out_pp;
         memset(cb, 0, cb_size);
 
+        rc = ata_pad_alloc(ap, dev);
+        if (rc)
+                goto err_out_pad;
+
         pp->cmd_block = cb;
         pp->cmd_block_dma = cb_dma;
 
         ap->private_data = pp;
 
         return 0;
+
+err_out_pad:
+        sil24_cblk_free(pp, dev);
+err_out_pp:
+        kfree(pp);
+err_out:
+        return rc;
 }
 
 static void sil24_port_stop(struct ata_port *ap)
 {
         struct device *dev = ap->host_set->dev;
         struct sil24_port_priv *pp = ap->private_data;
-        size_t cb_size = sizeof(*pp->cmd_block);
 
-        dma_free_coherent(dev, cb_size, pp->cmd_block, pp->cmd_block_dma);
+        sil24_cblk_free(pp, dev);
         kfree(pp);
 }
 
diff --git a/drivers/scsi/sata_sx4.c b/drivers/scsi/sata_sx4.c
index 0ec21e09f5d8..f859bbd681ed 100644
--- a/drivers/scsi/sata_sx4.c
+++ b/drivers/scsi/sata_sx4.c
@@ -450,14 +450,14 @@ static inline void pdc20621_host_pkt(struct ata_taskfile *tf, u8 *buf,
 
 static void pdc20621_dma_prep(struct ata_queued_cmd *qc)
 {
-        struct scatterlist *sg = qc->sg;
+        struct scatterlist *sg;
         struct ata_port *ap = qc->ap;
         struct pdc_port_priv *pp = ap->private_data;
         void __iomem *mmio = ap->host_set->mmio_base;
         struct pdc_host_priv *hpriv = ap->host_set->private_data;
         void __iomem *dimm_mmio = hpriv->dimm_mmio;
         unsigned int portno = ap->port_no;
-        unsigned int i, last, idx, total_len = 0, sgt_len;
+        unsigned int i, idx, total_len = 0, sgt_len;
         u32 *buf = (u32 *) &pp->dimm_buf[PDC_DIMM_HEADER_SZ];
 
         assert(qc->flags & ATA_QCFLAG_DMAMAP);
@@ -470,12 +470,11 @@ static void pdc20621_dma_prep(struct ata_queued_cmd *qc)
         /*
          * Build S/G table
          */
-        last = qc->n_elem;
         idx = 0;
-        for (i = 0; i < last; i++) {
-                buf[idx++] = cpu_to_le32(sg_dma_address(&sg[i]));
-                buf[idx++] = cpu_to_le32(sg_dma_len(&sg[i]));
-                total_len += sg_dma_len(&sg[i]);
+        ata_for_each_sg(sg, qc) {
+                buf[idx++] = cpu_to_le32(sg_dma_address(sg));
+                buf[idx++] = cpu_to_le32(sg_dma_len(sg));
+                total_len += sg_dma_len(sg);
         }
         buf[idx - 1] |= cpu_to_le32(ATA_PRD_EOT);
         sgt_len = idx * 4;
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 0ba3af7a1236..dcd17e7458ab 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -155,6 +155,10 @@ enum {
         ATA_SHIFT_UDMA          = 0,
         ATA_SHIFT_MWDMA         = 8,
         ATA_SHIFT_PIO           = 11,
+
+        /* size of buffer to pad xfers ending on unaligned boundaries */
+        ATA_DMA_PAD_SZ          = 4,
+        ATA_DMA_PAD_BUF_SZ      = ATA_DMA_PAD_SZ * ATA_MAX_QUEUE,
         
         /* Masks for port functions */
         ATA_PORT_PRIMARY        = (1 << 0),
@@ -249,9 +253,12 @@ struct ata_queued_cmd {
         unsigned long           flags;          /* ATA_QCFLAG_xxx */
         unsigned int            tag;
         unsigned int            n_elem;
+        unsigned int            orig_n_elem;
 
         int                     dma_dir;
 
+        unsigned int            pad_len;
+
         unsigned int            nsect;
         unsigned int            cursect;
 
@@ -262,9 +269,11 @@ struct ata_queued_cmd {
         unsigned int            cursg_ofs;
 
         struct scatterlist      sgent;
+        struct scatterlist      pad_sgent;
         void                    *buf_virt;
 
-        struct scatterlist      *sg;
+        /* DO NOT iterate over __sg manually, use ata_for_each_sg() */
+        struct scatterlist      *__sg;
 
         ata_qc_cb_t             complete_fn;
 
@@ -310,6 +319,9 @@ struct ata_port {
         struct ata_prd          *prd;    /* our SG list */
         dma_addr_t              prd_dma; /* and its DMA mapping */
 
+        void                    *pad;   /* array of DMA pad buffers */
+        dma_addr_t              pad_dma;
+
         struct ata_ioports      ioaddr; /* ATA cmd/ctl/dma register blocks */
 
         u8                      ctl;    /* cache of ATA control register */
@@ -512,6 +524,31 @@ extern int pci_test_config_bits(struct pci_dev *pdev, const struct pci_bits *bit
 #endif /* CONFIG_PCI */
 
 
+static inline int
+ata_sg_is_last(struct scatterlist *sg, struct ata_queued_cmd *qc)
+{
+        if (sg == &qc->pad_sgent)
+                return 1;
+        if (qc->pad_len)
+                return 0;
+        if (((sg - qc->__sg) + 1) == qc->n_elem)
+                return 1;
+        return 0;
+}
+
+static inline struct scatterlist *
+ata_qc_next_sg(struct scatterlist *sg, struct ata_queued_cmd *qc)
+{
+        if (sg == &qc->pad_sgent)
+                return NULL;
+        if (++sg - qc->__sg < qc->n_elem)
+                return sg;
+        return qc->pad_len ? &qc->pad_sgent : NULL;
+}
+
+#define ata_for_each_sg(sg, qc) \
+        for (sg = qc->__sg; sg; sg = ata_qc_next_sg(sg, qc))
+
 static inline unsigned int ata_tag_valid(unsigned int tag)
 {
         return (tag < ATA_MAX_QUEUE) ? 1 : 0;
@@ -740,4 +777,17 @@ static inline unsigned int __ac_err_mask(u8 status)
         return mask;
 }
 
+static inline int ata_pad_alloc(struct ata_port *ap, struct device *dev)
+{
+        ap->pad_dma = 0;
+        ap->pad = dma_alloc_coherent(dev, ATA_DMA_PAD_BUF_SZ,
+                                     &ap->pad_dma, GFP_KERNEL);
+        return (ap->pad == NULL) ? -ENOMEM : 0;
+}
+
+static inline void ata_pad_free(struct ata_port *ap, struct device *dev)
+{
+        dma_free_coherent(dev, ATA_DMA_PAD_BUF_SZ, ap->pad, ap->pad_dma);
+}
+
 #endif /* __LINUX_LIBATA_H__ */