mmc: tmio_mmc: implement a bounce buffer for unaligned DMA

For example, with SDIO WLAN cards, some transfers happen with buffers at
odd addresses, whereas the SH-Mobile DMA engine requires even addresses
for SDHI. This patch extends the tmio driver with a bounce buffer, that
is used for single entry scatter-gather lists both for sending and
receiving. If we ever encounter unaligned transfers with multi-element
sg lists, this patch will have to be extended. For now it just falls
back to PIO in this and other unsupported cases.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

1 files changed, 83 insertions, 6 deletions

diff --git a/drivers/mmc/host/tmio_mmc.c b/drivers/mmc/host/tmio_mmc.c
index e04c032abb1c..595b7b3f160d 100644
--- a/drivers/mmc/host/tmio_mmc.c
+++ b/drivers/mmc/host/tmio_mmc.c
@@ -111,6 +111,8 @@
                 sd_ctrl_write32((host), CTL_STATUS, ~(i)); \
         } while (0)
 
+/* This is arbitrary, just noone needed any higher alignment yet */
+#define MAX_ALIGN 4
 
 struct tmio_mmc_host {
         void __iomem *ctl;
@@ -127,6 +129,7 @@ struct tmio_mmc_host {
 
         /* pio related stuff */
         struct scatterlist      *sg_ptr;
+        struct scatterlist      *sg_orig;
         unsigned int            sg_len;
         unsigned int            sg_off;
 
@@ -139,9 +142,13 @@ struct tmio_mmc_host {
         struct tasklet_struct   dma_issue;
 #ifdef CONFIG_TMIO_MMC_DMA
         unsigned int            dma_sglen;
+        u8                      bounce_buf[PAGE_CACHE_SIZE] __attribute__((aligned(MAX_ALIGN)));
+        struct scatterlist      bounce_sg;
 #endif
 };
 
+static void tmio_check_bounce_buffer(struct tmio_mmc_host *host);
+
 static u16 sd_ctrl_read16(struct tmio_mmc_host *host, int addr)
 {
         return readw(host->ctl + (addr << host->bus_shift));
@@ -180,6 +187,7 @@ static void tmio_mmc_init_sg(struct tmio_mmc_host *host, struct mmc_data *data)
 {
         host->sg_len = data->sg_len;
         host->sg_ptr = data->sg;
+        host->sg_orig = data->sg;
         host->sg_off = 0;
 }
 
@@ -438,6 +446,8 @@ static void tmio_mmc_do_data_irq(struct tmio_mmc_host *host)
         if (data->flags & MMC_DATA_READ) {
                 if (!host->chan_rx)
                         disable_mmc_irqs(host, TMIO_MASK_READOP);
+                else
+                        tmio_check_bounce_buffer(host);
                 dev_dbg(&host->pdev->dev, "Complete Rx request %p\n",
                         host->mrq);
         } else {
@@ -529,8 +539,7 @@ static void tmio_mmc_cmd_irq(struct tmio_mmc_host *host,
                         if (!host->chan_rx)
                                 enable_mmc_irqs(host, TMIO_MASK_READOP);
                 } else {
-                        struct dma_chan *chan = host->chan_tx;
-                        if (!chan)
+                        if (!host->chan_tx)
                                 enable_mmc_irqs(host, TMIO_MASK_WRITEOP);
                         else
                                 tasklet_schedule(&host->dma_issue);
@@ -612,6 +621,16 @@ out:
 }
 
 #ifdef CONFIG_TMIO_MMC_DMA
+static void tmio_check_bounce_buffer(struct tmio_mmc_host *host)
+{
+        if (host->sg_ptr == &host->bounce_sg) {
+                unsigned long flags;
+                void *sg_vaddr = tmio_mmc_kmap_atomic(host->sg_orig, &flags);
+                memcpy(sg_vaddr, host->bounce_buf, host->bounce_sg.length);
+                tmio_mmc_kunmap_atomic(sg_vaddr, &flags);
+        }
+}
+
 static void tmio_mmc_enable_dma(struct tmio_mmc_host *host, bool enable)
 {
 #if defined(CONFIG_SUPERH) || defined(CONFIG_ARCH_SHMOBILE)
@@ -634,11 +653,35 @@ static void tmio_dma_complete(void *arg)
 
 static void tmio_mmc_start_dma_rx(struct tmio_mmc_host *host)
 {
-        struct scatterlist *sg = host->sg_ptr;
+        struct scatterlist *sg = host->sg_ptr, *sg_tmp;
         struct dma_async_tx_descriptor *desc = NULL;
         struct dma_chan *chan = host->chan_rx;
+        struct mfd_cell *cell = host->pdev->dev.platform_data;
+        struct tmio_mmc_data *pdata = cell->driver_data;
         dma_cookie_t cookie;
-        int ret;
+        int ret, i;
+        bool aligned = true, multiple = true;
+        unsigned int align = (1 << pdata->dma->alignment_shift) - 1;
+
+        for_each_sg(sg, sg_tmp, host->sg_len, i) {
+                if (sg_tmp->offset & align)
+                        aligned = false;
+                if (sg_tmp->length & align) {
+                        multiple = false;
+                        break;
+                }
+        }
+
+        if ((!aligned && (host->sg_len > 1 || sg->length > PAGE_CACHE_SIZE ||
+                          align >= MAX_ALIGN)) || !multiple)
+                goto pio;
+
+        /* The only sg element can be unaligned, use our bounce buffer then */
+        if (!aligned) {
+                sg_init_one(&host->bounce_sg, host->bounce_buf, sg->length);
+                host->sg_ptr = &host->bounce_sg;
+                sg = host->sg_ptr;
+        }
 
         ret = dma_map_sg(&host->pdev->dev, sg, host->sg_len, DMA_FROM_DEVICE);
         if (ret > 0) {
@@ -661,6 +704,7 @@ static void tmio_mmc_start_dma_rx(struct tmio_mmc_host *host)
         dev_dbg(&host->pdev->dev, "%s(): mapped %d -> %d, cookie %d, rq %p\n",
                 __func__, host->sg_len, ret, cookie, host->mrq);
 
+pio:
         if (!desc) {
                 /* DMA failed, fall back to PIO */
                 if (ret >= 0)
@@ -684,11 +728,39 @@ static void tmio_mmc_start_dma_rx(struct tmio_mmc_host *host)
 
 static void tmio_mmc_start_dma_tx(struct tmio_mmc_host *host)
 {
-        struct scatterlist *sg = host->sg_ptr;
+        struct scatterlist *sg = host->sg_ptr, *sg_tmp;
         struct dma_async_tx_descriptor *desc = NULL;
         struct dma_chan *chan = host->chan_tx;
+        struct mfd_cell *cell = host->pdev->dev.platform_data;
+        struct tmio_mmc_data *pdata = cell->driver_data;
         dma_cookie_t cookie;
-        int ret;
+        int ret, i;
+        bool aligned = true, multiple = true;
+        unsigned int align = (1 << pdata->dma->alignment_shift) - 1;
+
+        for_each_sg(sg, sg_tmp, host->sg_len, i) {
+                if (sg_tmp->offset & align)
+                        aligned = false;
+                if (sg_tmp->length & align) {
+                        multiple = false;
+                        break;
+                }
+        }
+
+        if ((!aligned && (host->sg_len > 1 || sg->length > PAGE_CACHE_SIZE ||
+                          align >= MAX_ALIGN)) || !multiple)
+                goto pio;
+
+        /* The only sg element can be unaligned, use our bounce buffer then */
+        if (!aligned) {
+                unsigned long flags;
+                void *sg_vaddr = tmio_mmc_kmap_atomic(sg, &flags);
+                sg_init_one(&host->bounce_sg, host->bounce_buf, sg->length);
+                memcpy(host->bounce_buf, sg_vaddr, host->bounce_sg.length);
+                tmio_mmc_kunmap_atomic(sg_vaddr, &flags);
+                host->sg_ptr = &host->bounce_sg;
+                sg = host->sg_ptr;
+        }
 
         ret = dma_map_sg(&host->pdev->dev, sg, host->sg_len, DMA_TO_DEVICE);
         if (ret > 0) {
@@ -709,6 +781,7 @@ static void tmio_mmc_start_dma_tx(struct tmio_mmc_host *host)
         dev_dbg(&host->pdev->dev, "%s(): mapped %d -> %d, cookie %d, rq %p\n",
                 __func__, host->sg_len, ret, cookie, host->mrq);
 
+pio:
         if (!desc) {
                 /* DMA failed, fall back to PIO */
                 if (ret >= 0)
@@ -822,6 +895,10 @@ static void tmio_mmc_release_dma(struct tmio_mmc_host *host)
         }
 }
 #else
+static void tmio_check_bounce_buffer(struct tmio_mmc_host *host)
+{
+}
+
 static void tmio_mmc_start_dma(struct tmio_mmc_host *host,
                                struct mmc_data *data)
 {