From 46d179525a1f6d16957dcb4624517bc04142b3e7 Mon Sep 17 00:00:00 2001 From: Doug Anderson Date: Tue, 26 Apr 2016 10:03:58 +0200 Subject: [PATCH] mmc: dw_mmc: Wait for data transfer after response errors. According to the DesignWare state machine description, after we get a "response error" or "response CRC error" we move into data transfer mode. That means that we don't necessarily need to special case trying to deal with the failure right away. We can wait until we are notified that the data transfer is complete (with or without errors) and then we can deal with the failure. It may sound strange to defer dealing with a command that we know will fail anyway, but this appears to fix a bug. During tuning (CMD19) on a specific card on an rk3288-based system, we found that we could get a "response CRC error". Sending the stop command after the "response CRC error" would then throw the system into a confused state causing all future tuning phases to report failure. When in the confused state, the controller would show these (hex codes are interrupt status register): CMD ERR: 0x00000046 (cmd=19) CMD ERR: 0x0000004e (cmd=12) DATA ERR: 0x00000208 DATA ERR: 0x0000020c CMD ERR: 0x00000104 (cmd=19) CMD ERR: 0x00000104 (cmd=12) DATA ERR: 0x00000208 DATA ERR: 0x0000020c ... ... It is inherently difficult to deal with the complexity of trying to correctly send a stop command while a data transfer is taking place since you need to deal with different corner cases caused by the fact that the data transfer could complete (with errors or without errors) during various places in sending the stop command (dw_mci_stop_dma, send_stop_abort, etc) Instead of adding a bunch of extra complexity to deal with this, it seems much simpler to just use the more straightforward (and less error-prone) path of letting the data transfer finish. There shouldn't be any huge benefit to sending the stop command slightly earlier, anyway. Signed-off-by: Doug Anderson Signed-off-by: Enric Balletbo i Serra Cc: Alim Akhtar Signed-off-by: Jaehoon Chung Signed-off-by: Ulf Hansson --- drivers/mmc/host/dw_mmc.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c index b7c7a76b80d5..7e5e8b056c13 100644 --- a/drivers/mmc/host/dw_mmc.c +++ b/drivers/mmc/host/dw_mmc.c @@ -1761,6 +1761,33 @@ static void dw_mci_tasklet_func(unsigned long priv) } if (cmd->data && err) { + /* + * During UHS tuning sequence, sending the stop + * command after the response CRC error would + * throw the system into a confused state + * causing all future tuning phases to report + * failure. + * + * In such case controller will move into a data + * transfer state after a response error or + * response CRC error. Let's let that finish + * before trying to send a stop, so we'll go to + * STATE_SENDING_DATA. + * + * Although letting the data transfer take place + * will waste a bit of time (we already know + * the command was bad), it can't cause any + * errors since it's possible it would have + * taken place anyway if this tasklet got + * delayed. Allowing the transfer to take place + * avoids races and keeps things simple. + */ + if ((err != -ETIMEDOUT) && + (cmd->opcode == MMC_SEND_TUNING_BLOCK)) { + state = STATE_SENDING_DATA; + continue; + } + dw_mci_stop_dma(host); send_stop_abort(host, data); state = STATE_SENDING_STOP;