[3.5.y.z extended stable] Patch "mmc: atmel-mci: fix timeout errors in SDIO mode when using DMA" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    mmc: atmel-mci: fix timeout errors in SDIO mode when using DMA

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From d284808feffab7a60f95bc0486dd5fda9a5b893c Mon Sep 17 00:00:00 2001
From: Ludovic Desroches <ludovic.desroches at atmel.com>
Date: Wed, 20 Nov 2013 16:01:11 +0100
Subject: mmc: atmel-mci: fix timeout errors in SDIO mode when using DMA

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 at atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre at atmel.com>
Signed-off-by: Chris Ball <cjb at laptop.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/mmc/host/atmel-mci.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c
index ac472be..e27632e 100644
--- a/drivers/mmc/host/atmel-mci.c
+++ b/drivers/mmc/host/atmel-mci.c
@@ -1106,11 +1106,22 @@ static void atmci_start_request(struct atmel_mci *host,
 	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;
--
1.8.3.2