mailbox: bcm-pdc: Performance improvements

Three changes to improve performance in the PDC driver:
- disable and reenable interrupts while the interrupt handler is
running
- update rxin and txin descriptor indexes more efficiently
- group receive descriptor context into a structure and keep
context in a single array rather than five to improve locality
of reference

Signed-off-by: Rob Rice <rob.rice@broadcom.com>
Reviewed-by: Andy Gospodarek <gospo@broadcom.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

1 files changed, 49 insertions, 36 deletions

diff --git a/drivers/mailbox/bcm-pdc-mailbox.c b/drivers/mailbox/bcm-pdc-mailbox.c
index e7dc1a227713..8c2aa7c9c27f 100644
--- a/drivers/mailbox/bcm-pdc-mailbox.c
+++ b/drivers/mailbox/bcm-pdc-mailbox.c
@@ -260,6 +260,27 @@ struct pdc_ring_alloc {
         u32         size;    /* ring allocation size in bytes */
 };
 
+/*
+ * context associated with a receive descriptor.
+ * @rxp_ctx: opaque context associated with frame that starts at each
+ *           rx ring index.
+ * @dst_sg:  Scatterlist used to form reply frames beginning at a given ring
+ *           index. Retained in order to unmap each sg after reply is processed.
+ * @rxin_numd: Number of rx descriptors associated with the message that starts
+ *             at a descriptor index. Not set for every index. For example,
+ *             if descriptor index i points to a scatterlist with 4 entries,
+ *             then the next three descriptor indexes don't have a value set.
+ * @resp_hdr: Virtual address of buffer used to catch DMA rx status
+ * @resp_hdr_daddr: physical address of DMA rx status buffer
+ */
+struct pdc_rx_ctx {
+        void *rxp_ctx;
+        struct scatterlist *dst_sg;
+        u32  rxin_numd;
+        void *resp_hdr;
+        dma_addr_t resp_hdr_daddr;
+};
+
 /* PDC state structure */
 struct pdc_state {
         /* Index of the PDC whose state is in this structure instance */
@@ -377,11 +398,7 @@ struct pdc_state {
         /* Index of next rx descriptor to post. */
         u32  rxout;
 
-        /*
-         * opaque context associated with frame that starts at each
-         * rx ring index.
-         */
-        void *rxp_ctx[PDC_RING_ENTRIES];
+        struct pdc_rx_ctx rx_ctx[PDC_RING_ENTRIES];
 
         /*
          * Scatterlists used to form request and reply frames beginning at a
@@ -389,18 +406,6 @@ struct pdc_state {
          * is processed
          */
         struct scatterlist *src_sg[PDC_RING_ENTRIES];
-        struct scatterlist *dst_sg[PDC_RING_ENTRIES];
-
-        /*
-         * Number of rx descriptors associated with the message that starts
-         * at this descriptor index. Not set for every index. For example,
-         * if descriptor index i points to a scatterlist with 4 entries, then
-         * the next three descriptor indexes don't have a value set.
-         */
-        u32  rxin_numd[PDC_RING_ENTRIES];
-
-        void *resp_hdr[PDC_RING_ENTRIES];
-        dma_addr_t resp_hdr_daddr[PDC_RING_ENTRIES];
 
         struct dentry *debugfs_stats;  /* debug FS stats file for this PDC */
 
@@ -591,11 +596,11 @@ pdc_receive_one(struct pdc_state *pdcs)
         struct brcm_message mssg;
         u32 len, rx_status;
         u32 num_frags;
-        int i;
         u8 *resp_hdr;    /* virtual addr of start of resp message DMA header */
         u32 frags_rdy;   /* number of fragments ready to read */
         u32 rx_idx;      /* ring index of start of receive frame */
         dma_addr_t resp_hdr_daddr;
+        struct pdc_rx_ctx *rx_ctx;
 
         mbc = &pdcs->mbc;
         chan = &mbc->chans[0];
@@ -607,7 +612,8 @@ pdc_receive_one(struct pdc_state *pdcs)
          * to read.
          */
         frags_rdy = NRXDACTIVE(pdcs->rxin, pdcs->last_rx_curr, pdcs->nrxpost);
-        if ((frags_rdy == 0) || (frags_rdy < pdcs->rxin_numd[pdcs->rxin]))
+        if ((frags_rdy == 0) ||
+            (frags_rdy < pdcs->rx_ctx[pdcs->rxin].rxin_numd))
                 /* No response ready */
                 return -EAGAIN;
 
@@ -617,24 +623,23 @@ pdc_receive_one(struct pdc_state *pdcs)
         dma_unmap_sg(dev, pdcs->src_sg[pdcs->txin],
                      sg_nents(pdcs->src_sg[pdcs->txin]), DMA_TO_DEVICE);
 
-        for (i = 0; i < num_frags; i++)
-                pdcs->txin = NEXTTXD(pdcs->txin, pdcs->ntxpost);
+        pdcs->txin = (pdcs->txin + num_frags) & pdcs->ntxpost;
 
         dev_dbg(dev, "PDC %u reclaimed %d tx descriptors",
                 pdcs->pdc_idx, num_frags);
 
         rx_idx = pdcs->rxin;
-        num_frags = pdcs->rxin_numd[rx_idx];
+        rx_ctx = &pdcs->rx_ctx[rx_idx];
+        num_frags = rx_ctx->rxin_numd;
         /* Return opaque context with result */
-        mssg.ctx = pdcs->rxp_ctx[rx_idx];
-        pdcs->rxp_ctx[rx_idx] = NULL;
-        resp_hdr = pdcs->resp_hdr[rx_idx];
-        resp_hdr_daddr = pdcs->resp_hdr_daddr[rx_idx];
-        dma_unmap_sg(dev, pdcs->dst_sg[rx_idx],
-                     sg_nents(pdcs->dst_sg[rx_idx]), DMA_FROM_DEVICE);
+        mssg.ctx = rx_ctx->rxp_ctx;
+        rx_ctx->rxp_ctx = NULL;
+        resp_hdr = rx_ctx->resp_hdr;
+        resp_hdr_daddr = rx_ctx->resp_hdr_daddr;
+        dma_unmap_sg(dev, rx_ctx->dst_sg, sg_nents(rx_ctx->dst_sg),
+                     DMA_FROM_DEVICE);
 
-        for (i = 0; i < num_frags; i++)
-                pdcs->rxin = NEXTRXD(pdcs->rxin, pdcs->nrxpost);
+        pdcs->rxin = (pdcs->rxin + num_frags) & pdcs->nrxpost;
 
         dev_dbg(dev, "PDC %u reclaimed %d rx descriptors",
                 pdcs->pdc_idx, num_frags);
@@ -826,6 +831,7 @@ static int pdc_rx_list_init(struct pdc_state *pdcs, struct scatterlist *dst_sg,
         u32 rx_pkt_cnt = 1;     /* Adding a single rx buffer */
         dma_addr_t daddr;
         void *vaddr;
+        struct pdc_rx_ctx *rx_ctx;
 
         rx_avail = pdcs->nrxpost - NRXDACTIVE(pdcs->rxin, pdcs->rxout,
                                               pdcs->nrxpost);
@@ -849,15 +855,16 @@ static int pdc_rx_list_init(struct pdc_state *pdcs, struct scatterlist *dst_sg,
 
         /* This is always the first descriptor in the receive sequence */
         flags = D64_CTRL1_SOF;
-        pdcs->rxin_numd[pdcs->rx_msg_start] = 1;
+        pdcs->rx_ctx[pdcs->rx_msg_start].rxin_numd = 1;
 
         if (unlikely(pdcs->rxout == (pdcs->nrxd - 1)))
                 flags |= D64_CTRL1_EOT;
 
-        pdcs->rxp_ctx[pdcs->rxout] = ctx;
-        pdcs->dst_sg[pdcs->rxout] = dst_sg;
-        pdcs->resp_hdr[pdcs->rxout] = vaddr;
-        pdcs->resp_hdr_daddr[pdcs->rxout] = daddr;
+        rx_ctx = &pdcs->rx_ctx[pdcs->rxout];
+        rx_ctx->rxp_ctx = ctx;
+        rx_ctx->dst_sg = dst_sg;
+        rx_ctx->resp_hdr = vaddr;
+        rx_ctx->resp_hdr_daddr = daddr;
         pdc_build_rxd(pdcs, daddr, pdcs->pdc_resp_hdr_len, flags);
         return PDC_SUCCESS;
 }
@@ -925,7 +932,7 @@ static int pdc_rx_list_sg_add(struct pdc_state *pdcs, struct scatterlist *sg)
                 desc_w++;
                 sg = sg_next(sg);
         }
-        pdcs->rxin_numd[pdcs->rx_msg_start] += desc_w;
+        pdcs->rx_ctx[pdcs->rx_msg_start].rxin_numd += desc_w;
 
         return PDC_SUCCESS;
 }
@@ -954,6 +961,9 @@ static irqreturn_t pdc_irq_handler(int irq, void *data)
         /* Clear interrupt flags in device */
         iowrite32(intstatus, pdcs->pdc_reg_vbase + PDC_INTSTATUS_OFFSET);
 
+        /* Disable interrupts until soft handler runs */
+        iowrite32(0, pdcs->pdc_reg_vbase + PDC_INTMASK_OFFSET);
+
         /* Wakeup IRQ thread */
         if (likely(pdcs && (irq == pdcs->pdc_irq) &&
                    (intstatus & PDC_INTMASK))) {
@@ -971,6 +981,9 @@ static void pdc_tasklet_cb(unsigned long data)
         rx_int = test_and_clear_bit(PDC_RCVINT_0, &pdcs->intstatus);
         if (likely(pdcs && rx_int))
                 pdc_receive(pdcs);
+
+        /* reenable interrupts */
+        iowrite32(PDC_INTMASK, pdcs->pdc_reg_vbase + PDC_INTMASK_OFFSET);
 }
 
 /**