sdhci: use PIO when DMA can't satisfy the request

Some controllers have been designed on the assumption that all transfers
will be 32-bit aligned, both in start address and in size. This is not a
guarantee the SDHCI specification provides and not one we can provide.

Revert back to PIO for individual requests in order to work around the
hardware bug.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

2 files changed, 31 insertions, 4 deletions

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 758a7417eb50..a5300f238d98 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -43,6 +43,10 @@ static unsigned int debug_quirks = 0;
 #define SDHCI_QUIRK_RESET_CMD_DATA_ON_IOS               (1<<4)
 /* Controller has an unusable DMA engine */
 #define SDHCI_QUIRK_BROKEN_DMA                          (1<<5)
+/* Controller can only DMA from 32-bit aligned addresses */
+#define SDHCI_QUIRK_32BIT_DMA_ADDR                      (1<<6)
+/* Controller can only DMA chunk sizes that are a multiple of 32 bits */
+#define SDHCI_QUIRK_32BIT_DMA_SIZE                      (1<<7)
 
 static const struct pci_device_id pci_ids[] __devinitdata = {
         {
@@ -429,7 +433,29 @@ static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_data *data)
 
         writeb(count, host->ioaddr + SDHCI_TIMEOUT_CONTROL);
 
-        if (host->flags & SDHCI_USE_DMA) {
+        if (host->flags & SDHCI_USE_DMA)
+                host->flags |= SDHCI_REQ_USE_DMA;
+
+        if (unlikely((host->flags & SDHCI_REQ_USE_DMA) &&
+                (host->chip->quirks & SDHCI_QUIRK_32BIT_DMA_SIZE) &&
+                ((data->blksz * data->blocks) & 0x3))) {
+                DBG("Reverting to PIO because of transfer size (%d)\n",
+                        data->blksz * data->blocks);
+                host->flags &= ~SDHCI_REQ_USE_DMA;
+        }
+
+        /*
+         * The assumption here being that alignment is the same after
+         * translation to device address space.
+         */
+        if (unlikely((host->flags & SDHCI_REQ_USE_DMA) &&
+                (host->chip->quirks & SDHCI_QUIRK_32BIT_DMA_ADDR) &&
+                (data->sg->offset & 0x3))) {
+                DBG("Reverting to PIO because of bad alignment\n");
+                host->flags &= ~SDHCI_REQ_USE_DMA;
+        }
+
+        if (host->flags & SDHCI_REQ_USE_DMA) {
                 int count;
 
                 count = pci_map_sg(host->chip->pdev, data->sg, data->sg_len,
@@ -466,7 +492,7 @@ static void sdhci_set_transfer_mode(struct sdhci_host *host,
                 mode |= SDHCI_TRNS_MULTI;
         if (data->flags & MMC_DATA_READ)
                 mode |= SDHCI_TRNS_READ;
-        if (host->flags & SDHCI_USE_DMA)
+        if (host->flags & SDHCI_REQ_USE_DMA)
                 mode |= SDHCI_TRNS_DMA;
 
         writew(mode, host->ioaddr + SDHCI_TRANSFER_MODE);
@@ -482,7 +508,7 @@ static void sdhci_finish_data(struct sdhci_host *host)
         data = host->data;
         host->data = NULL;
 
-        if (host->flags & SDHCI_USE_DMA) {
+        if (host->flags & SDHCI_REQ_USE_DMA) {
                 pci_unmap_sg(host->chip->pdev, data->sg, data->sg_len,
                         (data->flags & MMC_DATA_READ)?PCI_DMA_FROMDEVICE:PCI_DMA_TODEVICE);
         }
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index 05195ea900f4..e4d77b038bfa 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -171,7 +171,8 @@ struct sdhci_host {
         spinlock_t              lock;           /* Mutex */
 
         int                     flags;          /* Host attributes */
-#define SDHCI_USE_DMA           (1<<0)
+#define SDHCI_USE_DMA           (1<<0)          /* Host is DMA capable */
+#define SDHCI_REQ_USE_DMA       (1<<1)          /* Use DMA for this req. */
 
         unsigned int            max_clk;        /* Max possible freq (MHz) */
         unsigned int            timeout_clk;    /* Timeout freq (KHz) */