target/linux/brcm2708/patches-4.14/950-0434-mmc-bcm2835-Recover-from-MMC_SEND_EXT_CSD.patch

   1 From c2eae29f6503cf29ac6a204c51132cfed33d203e Mon Sep 17 00:00:00 2001
   2 From: Phil Elwell <phil@raspberrypi.org>
   3 Date: Fri, 26 Oct 2018 17:40:44 +0100
   4 Subject: [PATCH 434/454] mmc/bcm2835: Recover from MMC_SEND_EXT_CSD
   5
   6 If the user issues an "mmc extcsd read", the SD controller receives
   7 what it thinks is a SEND_IF_COND command with an unexpected data block.
   8 The resulting operations leave the FSM stuck in READWAIT, a state which
   9 persists until the MMC framework resets the controller, by which point
  10 the root filesystem is likely to have been unmounted.
  11
  12 A less heavyweight solution is to detect the condition and nudge the
  13 FSM by asserting the (self-clearing) FORCE_DATA_MODE bit.
  14
  15 N.B. This workaround was essentially discovered by accident and without
  16 a full understanding the inner workings of the controller, so it is
  17 fortunate that the "fix" only modifies error paths.
  18
  19 See: https://github.com/raspberrypi/linux/issues/2728
  20
  21 Signed-off-by: Phil Elwell <phil@raspberrypi.org>
  22 ---
  23  drivers/mmc/host/bcm2835.c | 9 +++++++++
  24  1 file changed, 9 insertions(+)
  25
  26 --- a/drivers/mmc/host/bcm2835.c
  27 +++ b/drivers/mmc/host/bcm2835.c
  28 @@ -772,6 +772,8 @@ static void bcm2835_finish_command(struc
  29
  30                 if (!(sdhsts & SDHSTS_CRC7_ERROR) ||
  31                     (host->cmd->opcode != MMC_SEND_OP_COND)) {
  32 +                       u32 edm, fsm;
  33 +
  34                         if (sdhsts & SDHSTS_CMD_TIME_OUT) {
  35                                 host->cmd->error = -ETIMEDOUT;
  36                         } else {
  37 @@ -780,6 +782,13 @@ static void bcm2835_finish_command(struc
  38                                 bcm2835_dumpregs(host);
  39                                 host->cmd->error = -EILSEQ;
  40                         }
  41 +                       edm = readl(host->ioaddr + SDEDM);
  42 +                       fsm = edm & SDEDM_FSM_MASK;
  43 +                       if (fsm == SDEDM_FSM_READWAIT ||
  44 +                           fsm == SDEDM_FSM_WRITESTART1)
  45 +                               /* Kick the FSM out of its wait */
  46 +                               writel(edm | SDEDM_FORCE_DATA_MODE,
  47 +                                      host->ioaddr + SDEDM);
  48                         bcm2835_finish_request(host);
  49                         return;
  50                 }