[MMC] sdhci: Avoid sdhci DMA boundaries

The sdhci controllers will issue an interrupt when a configurable number of
bytes have been transfered using DMA. The purpose is to handle multiple,
scattered memory pages.

Unfortunately, it requires that all transfers are completely aligned to
memory pages, which we cannot guarantee. So we just disable the function.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 10 insertions, 4 deletions

diff --git a/drivers/mmc/sdhci.c b/drivers/mmc/sdhci.c
index 8e480140cd28..95fe0fdac484 100644
--- a/drivers/mmc/sdhci.c
+++ b/drivers/mmc/sdhci.c
@@ -326,6 +326,9 @@ static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_data *data)
         DBG("tsac %d ms nsac %d clk\n",
                 data->timeout_ns / 1000000, data->timeout_clks);
 
+        /* Sanity checks */
+        BUG_ON(data->blksz * data->blocks > 524288);
+
         /* timeout in us */
         target_timeout = data->timeout_ns / 1000 +
                 data->timeout_clks / host->clock;
@@ -375,7 +378,9 @@ static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_data *data)
                 host->remain = host->cur_sg->length;
         }
 
-        writew(data->blksz, host->ioaddr + SDHCI_BLOCK_SIZE);
+        /* We do not handle DMA boundaries, so set it to max (512 KiB) */
+        writew(SDHCI_MAKE_BLKSZ(7, data->blksz),
+                host->ioaddr + SDHCI_BLOCK_SIZE);
         writew(data->blocks, host->ioaddr + SDHCI_BLOCK_COUNT);
 }
 
@@ -1188,10 +1193,10 @@ static int __devinit sdhci_probe_slot(struct pci_dev *pdev, int slot)
         mmc->max_phys_segs = 16;
 
         /*
-         * Maximum number of sectors in one transfer. Limited by sector
-         * count register.
+         * Maximum number of sectors in one transfer. Limited by DMA boundary
+         * size (512KiB), which means (512 KiB/512=) 1024 entries.
          */
-        mmc->max_sectors = 0x3FFF;
+        mmc->max_sectors = 1024;
 
         /*
          * Maximum segment size. Could be one segment with the maximum number
diff --git a/drivers/mmc/sdhci.h b/drivers/mmc/sdhci.h
index f8df28f8d6dd..8ed2a8973db6 100644
--- a/drivers/mmc/sdhci.h
+++ b/drivers/mmc/sdhci.h
@@ -23,6 +23,7 @@
 #define SDHCI_DMA_ADDRESS       0x00
 
 #define SDHCI_BLOCK_SIZE        0x04
+#define  SDHCI_MAKE_BLKSZ(dma, blksz) (((dma & 0x7) << 12) | (blksz & 0xFFF))
 
 #define SDHCI_BLOCK_COUNT       0x06