mmc: bcm2835: Recover from MMC_SEND_EXT_CSD

If the user issues an "mmc extcsd read", the SD controller receives
what it thinks is a SEND_IF_COND command with an unexpected data block.
The resulting operations leave the FSM stuck in READWAIT, a state which
persists until the MMC framework resets the controller, by which point
the root filesystem is likely to have been unmounted.

A less heavyweight solution is to detect the condition and nudge the
FSM by asserting the (self-clearing) FORCE_DATA_MODE bit.

Link: https://github.com/raspberrypi/linux/issues/2728
Signed-off-by: Phil Elwell <phil@raspberrypi.org>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/mmc/host/bcm2835.c b/drivers/mmc/host/bcm2835.c
index beec8d0..096e737 100644 (file)
--- a/drivers/mmc/host/bcm2835.c
+++ b/drivers/mmc/host/bcm2835.c
@@ -762,6 +762,8 @@ static void bcm2835_finish_command(struct bcm2835_host *host)
 
                if (!(sdhsts & SDHSTS_CRC7_ERROR) ||
                    (host->cmd->opcode != MMC_SEND_OP_COND)) {
+                       u32 edm, fsm;
+
                        if (sdhsts & SDHSTS_CMD_TIME_OUT) {
                                host->cmd->error = -ETIMEDOUT;
                        } else {
@@ -770,6 +772,13 @@ static void bcm2835_finish_command(struct bcm2835_host *host)
                                bcm2835_dumpregs(host);
                                host->cmd->error = -EILSEQ;
                        }
+                       edm = readl(host->ioaddr + SDEDM);
+                       fsm = edm & SDEDM_FSM_MASK;
+                       if (fsm == SDEDM_FSM_READWAIT ||
+                           fsm == SDEDM_FSM_WRITESTART1)
+                               /* Kick the FSM out of its wait */
+                               writel(edm | SDEDM_FORCE_DATA_MODE,
+                                      host->ioaddr + SDEDM);
                        bcm2835_finish_request(host);
                        return;
                }