[U-Boot] [PATCH] MMC: PL180: Fix infinite loop with VExpress extended fifo implementation

[Jon Medhurst (Tixy)]

From: Jon Medhurst <jon.medhurst at linaro.org>

The new IO FPGA implementation for Versatile Express contains an MMCI
(PL180) cell with the FIFO extended to 128 words. This causes the
read_bytes() function to go into an infinite loop; as it will wait for
for the half-full signal (SDI_STA_RXFIFOBR) if there are more than 8
words remaining (SDI_FIFO_BURST_SIZE), but it won't receive this signal
once there are fewer than 64 words left to transfer.

One possible fix is to add some build time configuration to change
SDI_FIFO_BURST_SIZE for the new implementation. However, the problematic
code only seems to exist as a small performance optimisation, so the
solution implemented by this patch is to simply remove it. The error
checking following the loop is also removed as this will be handled by
code further down the function.

Cc: Andy Fleming <afleming at gmail.com>
Signed-off-by: Jon Medhurst <jon.medhurst at linaro.org>
---

If it is desirable to keep the burst read optimisation, then an
alternative solution would be to keep the loop and add an if clause to
do a single read if the fifo doesn't have enough for a burst.

---
 drivers/mmc/arm_pl180_mmci.c |   26 --------------------------
 1 files changed, 0 insertions(+), 26 deletions(-)

diff --git a/drivers/mmc/arm_pl180_mmci.c b/drivers/mmc/arm_pl180_mmci.c
index ed296ee..e6467a2 100644
--- a/drivers/mmc/arm_pl180_mmci.c
+++ b/drivers/mmc/arm_pl180_mmci.c
@@ -111,7 +111,6 @@ static int do_command(struct mmc *dev, struct mmc_cmd *cmd)
 static int read_bytes(struct mmc *dev, u32 *dest, u32 blkcount, u32 blksize)
 {
        u32 *tempbuff = dest;
-       int i;
        u64 xfercount = blkcount * blksize;
        struct mmc_host *host = dev->priv;
        u32 status, status_err;
@@ -121,31 +120,6 @@ static int read_bytes(struct mmc *dev, u32 *dest, u32 blkcount, u32 blksize)
        status = readl(&host->base->status);
        status_err = status & (SDI_STA_DCRCFAIL | SDI_STA_DTIMEOUT |
                               SDI_STA_RXOVERR);
-       while (!status_err &&
-              (xfercount >= SDI_FIFO_BURST_SIZE * sizeof(u32))) {
-               if (status & SDI_STA_RXFIFOBR) {
-                       for (i = 0; i < SDI_FIFO_BURST_SIZE; i++)
-                               *(tempbuff + i) = readl(&host->base->fifo);
-                       tempbuff += SDI_FIFO_BURST_SIZE;
-                       xfercount -= SDI_FIFO_BURST_SIZE * sizeof(u32);
-               }
-               status = readl(&host->base->status);
-               status_err = status &
-                       (SDI_STA_DCRCFAIL | SDI_STA_DTIMEOUT | SDI_STA_RXOVERR);
-       }
-
-       if (status & SDI_STA_DTIMEOUT) {
-               printf("Read data timed out, xfercount: %llu, status: 0x%08X\n",
-                       xfercount, status);
-               return -ETIMEDOUT;
-       } else if (status & SDI_STA_DCRCFAIL) {
-               printf("Read data blk CRC error: 0x%x\n", status);
-               return -EILSEQ;
-       } else if (status & SDI_STA_RXOVERR) {
-               printf("Read data RX overflow error\n");
-               return -EIO;
-       }
-
        while ((!status_err) && (xfercount >= sizeof(u32))) {
                if (status & SDI_STA_RXDAVL) {
                        *(tempbuff) = readl(&host->base->fifo);
-- 
1.7.4.1