linux-kernel - [PATCH] mmc: dw_mmc: Reset DMA before enabling IDMAC

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Message-Id: <1412618020-22278-1-git-send-email-sonnyrao@chromium.org>
Date:	Mon,  6 Oct 2014 10:53:40 -0700
From:	Sonny Rao <sonnyrao@...omium.org>
To:	linux-mmc@...r.kernel.org
Cc:	Heiko Stuebner <heiko@...ech.de>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Ulf Hansson <ulf.hansson@...aro.org>, dianders@...omium.org,
	eddie.cai@...k-chips.com, addy.ke@...k-chips.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Sonny Rao <sonnyrao@...omium.org>
Subject: [PATCH] mmc: dw_mmc: Reset DMA before enabling IDMAC

We've already got a reset of DMA after it's done.  Add one before we
start DMA too.  This fixes a data corruption on Rockchip SoCs which
will get bad data when doing a DMA transfer after doing a PIO transfer.

We tested this on an Exynos 5800 with HS200 and didn't notice any
difference in sequential read throughput.

Signed-off-by: Sonny Rao <sonnyrao@...omium.org>
Signed-off-by: Doug Anderson <dianders@...omium.org>
---
 drivers/mmc/host/dw_mmc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 69f0cc6..2b5401e 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -83,6 +83,7 @@ struct idmac_desc {
 #endif /* CONFIG_MMC_DW_IDMAC */
 
 static bool dw_mci_reset(struct dw_mci *host);
+static bool dw_mci_ctrl_reset(struct dw_mci *host, u32 reset);
 
 #if defined(CONFIG_DEBUG_FS)
 static int dw_mci_req_show(struct seq_file *s, void *v)
@@ -448,6 +449,9 @@ static void dw_mci_idmac_start_dma(struct dw_mci *host, unsigned int sg_len)
 
 	dw_mci_translate_sglist(host, host->data, sg_len);
 
+	/* Make sure to reset DMA in case we did PIO before this */
+	dw_mci_ctrl_reset(host, SDMMC_CTRL_DMA_RESET);
+
 	/* Select IDMAC interface */
 	temp = mci_readl(host, CTRL);
 	temp |= SDMMC_CTRL_USE_IDMAC;
-- 
1.8.3.2

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