linux-kernel - [PATCH 3.2 033/200] mmc: atmel-mci: fix timeout errors in SDIO mode when using DMA

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Message-ID: <lsq.1396221815.728347403@decadent.org.uk>
Date:	Mon, 31 Mar 2014 00:23:35 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Nicolas Ferre" <nicolas.ferre@...el.com>,
	"Ludovic Desroches" <ludovic.desroches@...el.com>,
	"Chris Ball" <cjb@...top.org>
Subject: [PATCH 3.2 033/200] mmc: atmel-mci: fix timeout errors in SDIO
 mode when using DMA

3.2.56-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ludovic Desroches <ludovic.desroches@...el.com>

commit 66b512eda74d59b17eac04c4da1b38d82059e6c9 upstream.

With some SDIO devices, timeout errors can happen when reading data.
To solve this issue, the DMA transfer has to be activated before sending
the command to the device. This order is incorrect in PDC mode. So we
have to take care if we are using DMA or PDC to know when to send the
MMC command.

Signed-off-by: Ludovic Desroches <ludovic.desroches@...el.com>
Acked-by: Nicolas Ferre <nicolas.ferre@...el.com>
Signed-off-by: Chris Ball <cjb@...top.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/mmc/host/atmel-mci.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

--- a/drivers/mmc/host/atmel-mci.c
+++ b/drivers/mmc/host/atmel-mci.c
@@ -1014,11 +1014,22 @@ static void atmci_start_request(struct a
 	iflags |= ATMCI_CMDRDY;
 	cmd = mrq->cmd;
 	cmdflags = atmci_prepare_command(slot->mmc, cmd);
-	atmci_send_command(host, cmd, cmdflags);
+
+	/*
+	 * DMA transfer should be started before sending the command to avoid
+	 * unexpected errors especially for read operations in SDIO mode.
+	 * Unfortunately, in PDC mode, command has to be sent before starting
+	 * the transfer.
+	 */
+	if (host->submit_data != &atmci_submit_data_dma)
+		atmci_send_command(host, cmd, cmdflags);
 
 	if (data)
 		host->submit_data(host, data);
 
+	if (host->submit_data == &atmci_submit_data_dma)
+		atmci_send_command(host, cmd, cmdflags);
+
 	if (mrq->stop) {
 		host->stop_cmdr = atmci_prepare_command(slot->mmc, mrq->stop);
 		host->stop_cmdr |= ATMCI_CMDR_STOP_XFER;

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