From 6191e47f23fe4fa13dfbb38dfdda12e567028963 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Fri, 26 Oct 2018 17:29:51 +0100
Subject: [PATCH 433/454] mmc/bcm2835-sdhost: 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 <phil@raspberrypi.org>
---
 drivers/mmc/host/bcm2835-sdhost.c | 9 +++++++++
 1 file changed, 9 insertions(+)

--- a/drivers/mmc/host/bcm2835-sdhost.c
+++ b/drivers/mmc/host/bcm2835-sdhost.c
@@ -1244,6 +1244,8 @@ static void bcm2835_sdhost_finish_comman
 				pr_info("%s: ignoring CRC7 error for CMD1\n",
 					mmc_hostname(host->mmc));
 		} else {
+			u32 edm, fsm;
+
 			if (sdhsts & SDHSTS_CMD_TIME_OUT) {
 				if (host->debug)
 					pr_warn("%s: command %d timeout\n",
@@ -1256,6 +1258,13 @@ static void bcm2835_sdhost_finish_comman
 				       host->cmd->opcode);
 				host->cmd->error = -EILSEQ;
 			}
+
+			edm = readl(host->ioaddr + SDEDM);
+			fsm = edm & SDEDM_FSM_MASK;
+			if (fsm == SDEDM_FSM_READWAIT ||
+			    fsm == SDEDM_FSM_WRITESTART1)
+				writel(edm | SDEDM_FORCE_DATA_MODE,
+				       host->ioaddr + SDEDM);
 			tasklet_schedule(&host->finish_tasklet);
 			return;
 		}
