s3cmci: DMA fixes

Fixes for the DMA transfer mode of the driver to try and improve the state
of the code:

- Ensure that dma_complete is set during the end of the command phase
  so that transfers do not stall awaiting the completion

- Update the DMA debugging to provide a bit more useful information
  such as how many DMA descriptors where not processed and print the
  DMA addresses in hexadecimal.

- Fix the DMA channel request code to actually request DMA for the
  S3CMCI block instead of whatever '0' signified.

- Add fallback to PIO if we cannot get the DMA channel, as many of the
  devices with this block only have a limited number of DMA channels.

- Only try and claim and free the DMA channel if we are trying to use it.

This improves the driver DMA code to the point where it can now identify a
card and read the partition table.  However the DMA can still stall when
trying to move data between the host and memory.

Signed-off-by: Ben Dooks <ben@simtec.co.uk>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 47 insertions, 18 deletions

diff --git a/drivers/mmc/host/s3cmci.c b/drivers/mmc/host/s3cmci.c
index 0adf31895f2a..0af972275d45 100644
--- a/drivers/mmc/host/s3cmci.c
+++ b/drivers/mmc/host/s3cmci.c
@@ -183,6 +183,21 @@ static inline bool s3cmci_host_usedma(struct s3cmci_host *host)
 #endif
 }
 
+/**
+ * s3cmci_host_canpio - return true if host has pio code available
+ *
+ * Return true if the driver has been compiled with the PIO support code
+ * available.
+ */
+static inline bool s3cmci_host_canpio(void)
+{
+#ifdef CONFIG_MMC_S3C_PIO
+        return true;
+#else
+        return false;
+#endif
+}
+
 static inline u32 enable_imask(struct s3cmci_host *host, u32 imask)
 {
         u32 newmask;
@@ -786,6 +801,7 @@ static void s3cmci_dma_done_callback(struct s3c2410_dma_chan *dma_ch,
         dbg(host, dbg_dma, "DMA FINISHED Size:%i DSTA:%08x DCNT:%08x\n",
                 size, mci_dsta, mci_dcnt);
 
+        host->dma_complete = 1;
         host->complete_what = COMPLETION_FINALIZE;
 
 out:
@@ -816,7 +832,8 @@ static void finalize_request(struct s3cmci_host *host)
         if (cmd->data && (cmd->error == 0) &&
             (cmd->data->error == 0)) {
                 if (s3cmci_host_usedma(host) && (!host->dma_complete)) {
-                        dbg(host, dbg_dma, "DMA Missing!\n");
+                        dbg(host, dbg_dma, "DMA Missing (%d)!\n",
+                            host->dma_complete);
                         return;
                 }
         }
@@ -1065,7 +1082,7 @@ static int s3cmci_prepare_pio(struct s3cmci_host *host, struct mmc_data *data)
 static int s3cmci_prepare_dma(struct s3cmci_host *host, struct mmc_data *data)
 {
         int dma_len, i;
-        int rw = (data->flags & MMC_DATA_WRITE) ? 1 : 0;
+        int rw = data->flags & MMC_DATA_WRITE;
 
         BUG_ON((data->flags & BOTH_DIR) == BOTH_DIR);
 
@@ -1073,7 +1090,7 @@ static int s3cmci_prepare_dma(struct s3cmci_host *host, struct mmc_data *data)
         s3c2410_dma_ctrl(host->dma, S3C2410_DMAOP_FLUSH);
 
         dma_len = dma_map_sg(mmc_dev(host->mmc), data->sg, data->sg_len,
-                             (rw) ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
+                             rw ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
 
         if (dma_len == 0)
                 return -ENOMEM;
@@ -1084,11 +1101,11 @@ static int s3cmci_prepare_dma(struct s3cmci_host *host, struct mmc_data *data)
         for (i = 0; i < dma_len; i++) {
                 int res;
 
-                dbg(host, dbg_dma, "enqueue %i:%u@%u\n", i,
-                        sg_dma_address(&data->sg[i]),
-                        sg_dma_len(&data->sg[i]));
+                dbg(host, dbg_dma, "enqueue %i: %08x@%u\n", i,
+                    sg_dma_address(&data->sg[i]),
+                    sg_dma_len(&data->sg[i]));
 
-                res = s3c2410_dma_enqueue(host->dma, (void *) host,
+                res = s3c2410_dma_enqueue(host->dma, host,
                                           sg_dma_address(&data->sg[i]),
                                           sg_dma_len(&data->sg[i]));
 
@@ -1581,8 +1598,6 @@ static int __devinit s3cmci_probe(struct platform_device *pdev)
         host->complete_what     = COMPLETION_NONE;
         host->pio_active        = XFER_NONE;
 
-        host->dma               = S3CMCI_DMA;
-
 #ifdef CONFIG_MMC_S3C_PIODMA
         host->dodma             = host->pdata->dma;
 #endif
@@ -1665,10 +1680,21 @@ static int __devinit s3cmci_probe(struct platform_device *pdev)
                 gpio_direction_input(host->pdata->gpio_wprotect);
         }
 
-        if (s3c2410_dma_request(S3CMCI_DMA, &s3cmci_dma_client, NULL) < 0) {
-                dev_err(&pdev->dev, "unable to get DMA channel.\n");
-                ret = -EBUSY;
-                goto probe_free_gpio_wp;
+        /* depending on the dma state, get a dma channel to use. */
+
+        if (s3cmci_host_usedma(host)) {
+                host->dma = s3c2410_dma_request(DMACH_SDI, &s3cmci_dma_client,
+                                                host);
+                if (host->dma < 0) {
+                        dev_err(&pdev->dev, "cannot get DMA channel.\n");
+                        if (!s3cmci_host_canpio()) {
+                                ret = -EBUSY;
+                                goto probe_free_gpio_wp;
+                        } else {
+                                dev_warn(&pdev->dev, "falling back to PIO.\n");
+                                host->dodma = 0;
+                        }
+                }
         }
 
         host->clk = clk_get(&pdev->dev, "sdi");
@@ -1676,7 +1702,7 @@ static int __devinit s3cmci_probe(struct platform_device *pdev)
                 dev_err(&pdev->dev, "failed to find clock source.\n");
                 ret = PTR_ERR(host->clk);
                 host->clk = NULL;
-                goto probe_free_host;
+                goto probe_free_dma;
         }
 
         ret = clk_enable(host->clk);
@@ -1738,6 +1764,10 @@ static int __devinit s3cmci_probe(struct platform_device *pdev)
  clk_free:
         clk_put(host->clk);
 
+ probe_free_dma:
+        if (s3cmci_host_usedma(host))
+                s3c2410_dma_free(host->dma, &s3cmci_dma_client);
+
  probe_free_gpio_wp:
         if (host->pdata->gpio_wprotect)
                 gpio_free(host->pdata->gpio_wprotect);
@@ -1796,7 +1826,9 @@ static int __devexit s3cmci_remove(struct platform_device *pdev)
         clk_put(host->clk);
 
         tasklet_disable(&host->pio_tasklet);
-        s3c2410_dma_free(S3CMCI_DMA, &s3cmci_dma_client);
+
+        if (s3cmci_host_usedma(host))
+                s3c2410_dma_free(host->dma, &s3cmci_dma_client);
 
         free_irq(host->irq, host);
 
diff --git a/drivers/mmc/host/s3cmci.h b/drivers/mmc/host/s3cmci.h
index 62fac6602306..c76b53dbeb61 100644
--- a/drivers/mmc/host/s3cmci.h
+++ b/drivers/mmc/host/s3cmci.h
@@ -8,9 +8,6 @@
  * published by the Free Software Foundation.
  */
 
-/* FIXME: DMA Resource management ?! */
-#define S3CMCI_DMA 0
-
 enum s3cmci_waitfor {
         COMPLETION_NONE,
         COMPLETION_FINALIZE,