ARM: mmci: avoid reporting too many completed bytes on fifo overrun

The data counter counts the number of bytes transferred on the MMC bus.
When a FIFO overrun occurs, we will not have transferred a FIFOs-worth
of data to memory, and so the data counter will be a FIFOs-worth ahead.
If this occurs on a block boundary, we will report one too many sectors
as successful.  Fix this.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 18 insertions, 6 deletions

diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
index 2d6de3e03e2d..d7b83a8b3534 100644
--- a/drivers/mmc/host/mmci.c
+++ b/drivers/mmc/host/mmci.c
@@ -283,22 +283,34 @@ mmci_data_irq(struct mmci_host *host, struct mmc_data *data,
         if (status & (MCI_DATACRCFAIL|MCI_DATATIMEOUT|MCI_TXUNDERRUN|MCI_RXOVERRUN)) {
                 u32 remain, success;
 
-                /* Calculate how far we are into the transfer */
+                /*
+                 * Calculate how far we are into the transfer.  Note that
+                 * the data counter gives the number of bytes transferred
+                 * on the MMC bus, not on the host side.  On reads, this
+                 * can be as much as a FIFO-worth of data ahead.  This
+                 * matters for FIFO overruns only.
+                 */
                 remain = readl(host->base + MMCIDATACNT);
                 success = data->blksz * data->blocks - remain;
 
-                dev_dbg(mmc_dev(host->mmc), "MCI ERROR IRQ (status %08x)\n", status);
+                dev_dbg(mmc_dev(host->mmc), "MCI ERROR IRQ, status 0x%08x at 0x%08x\n",
+                        status, success);
                 if (status & MCI_DATACRCFAIL) {
                         /* Last block was not successful */
-                        host->data_xfered = round_down(success - 1, data->blksz);
+                        success -= 1;
                         data->error = -EILSEQ;
                 } else if (status & MCI_DATATIMEOUT) {
-                        host->data_xfered = round_down(success, data->blksz);
                         data->error = -ETIMEDOUT;
-                } else if (status & (MCI_TXUNDERRUN|MCI_RXOVERRUN)) {
-                        host->data_xfered = round_down(success, data->blksz);
+                } else if (status & MCI_TXUNDERRUN) {
+                        data->error = -EIO;
+                } else if (status & MCI_RXOVERRUN) {
+                        if (success > host->variant->fifosize)
+                                success -= host->variant->fifosize;
+                        else
+                                success = 0;
                         data->error = -EIO;
                 }
+                host->data_xfered = round_down(success, data->blksz);
 
                 /*
                  * We hit an error condition.  Ensure that any data