From c2eae29f6503cf29ac6a204c51132cfed33d203e Mon Sep 17 00:00:00 2001 From: Phil Elwell Date: Fri, 26 Oct 2018 17:40:44 +0100 Subject: [PATCH 434/454] 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. N.B. This workaround was essentially discovered by accident and without a full understanding the inner workings of the controller, so it is fortunate that the "fix" only modifies error paths. See: https://github.com/raspberrypi/linux/issues/2728 Signed-off-by: Phil Elwell --- drivers/mmc/host/bcm2835.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/drivers/mmc/host/bcm2835.c +++ b/drivers/mmc/host/bcm2835.c @@ -772,6 +772,8 @@ static void bcm2835_finish_command(struc 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 { @@ -780,6 +782,13 @@ static void bcm2835_finish_command(struc 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; }