linux-kernel - [PATCH] mmc: dw_mmc: Fix hang on data CRC error

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Message-ID: <20210630102232.16011-1-vincent.whitchurch@axis.com>
Date:   Wed, 30 Jun 2021 12:22:32 +0200
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     Jaehoon Chung <jh80.chung@...sung.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
CC:     <kernel@...s.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        <linux-mmc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] mmc: dw_mmc: Fix hang on data CRC error

When a Data CRC interrupt is received, the driver disables the DMA, then
sends the stop/abort command and then waits for Data Transfer Over.

However, sometimes, when a data CRC error is received in the middle of a
multi-block write transfer, the Data Transfer Over interrupt is never
received, and the driver hangs and never completes the request.

The driver sets the BMOD.SWR bit (SDMMC_IDMAC_SWRESET) when stopping the
DMA, but according to the manual CMD.STOP_ABORT_CMD should be programmed
"before assertion of SWR".  Do these operations in the recommended
order.  With this change the Data Transfer Over is always received
correctly in my tests.

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
---
 drivers/mmc/host/dw_mmc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index f85271f5c4fa..845b0745ea37 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -2083,8 +2083,8 @@ static void dw_mci_tasklet_func(struct tasklet_struct *t)
 					continue;
 				}
 
-				dw_mci_stop_dma(host);
 				send_stop_abort(host, data);
+				dw_mci_stop_dma(host);
 				state = STATE_SENDING_STOP;
 				break;
 			}
@@ -2108,10 +2108,10 @@ static void dw_mci_tasklet_func(struct tasklet_struct *t)
 			 */
 			if (test_and_clear_bit(EVENT_DATA_ERROR,
 					       &host->pending_events)) {
-				dw_mci_stop_dma(host);
 				if (!(host->data_status & (SDMMC_INT_DRTO |
 							   SDMMC_INT_EBE)))
 					send_stop_abort(host, data);
+				dw_mci_stop_dma(host);
 				state = STATE_DATA_ERROR;
 				break;
 			}
@@ -2144,10 +2144,10 @@ static void dw_mci_tasklet_func(struct tasklet_struct *t)
 			 */
 			if (test_and_clear_bit(EVENT_DATA_ERROR,
 					       &host->pending_events)) {
-				dw_mci_stop_dma(host);
 				if (!(host->data_status & (SDMMC_INT_DRTO |
 							   SDMMC_INT_EBE)))
 					send_stop_abort(host, data);
+				dw_mci_stop_dma(host);
 				state = STATE_DATA_ERROR;
 				break;
 			}
-- 
2.28.0