2014-12-11 01:29:15 +00:00
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From 7b4540118f9d125ed8cf51f80aa429d1a7f5bc94 Mon Sep 17 00:00:00 2001
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2014-12-01 04:11:11 +00:00
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From: Andrew Lunn <andrew@lunn.ch>
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Date: Wed, 12 Nov 2014 23:10:08 +0100
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2014-12-11 01:29:15 +00:00
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Subject: [PATCH 5/5] mmc: mvsdio: Work around broken TX DMA
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2014-12-01 04:11:11 +00:00
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In order to use the mvsdio driver for sdio, it has been necessary to
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use a module parameter to disable DMA so to force PIO is used. It is
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then possible to use wireless LAN devices like mwifiex found on
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topkick and mirabox. However, accessing an MMC SD card does work with
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DMA.
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Investigation has shown that MMC block device accesses are always
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aligned to 64 byte boundaries, where as transfers from mwifiex are
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rarely more than word aligned. It has also been determined that card
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to host transfers work with DMA for SDIO devices, but host to card
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transfers with DMA have problems.
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This patch extends the current checks for buffers which are not word
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aligned or multiple of words. All host to card transfers which are not
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64 byte aligned are now also performed via PIO. This should not affect
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the performance of SD cards, but allow sdio devices to work out of the
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box, and they are likely to be more efficient since DMA will be used
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for card to host transfers.
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Tested on mirabox for wifi via mwifiex
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Tested on 370 RD for file systems on an SD card.
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Signed-off-by: Andrew Lunn <andrew@lunn.ch>
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Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
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---
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drivers/mmc/host/mvsdio.c | 7 ++++++-
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1 file changed, 6 insertions(+), 1 deletion(-)
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diff --git a/drivers/mmc/host/mvsdio.c b/drivers/mmc/host/mvsdio.c
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2014-12-11 01:29:15 +00:00
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index 9f50234..ab95bb7 100644
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2014-12-01 04:11:11 +00:00
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--- a/drivers/mmc/host/mvsdio.c
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+++ b/drivers/mmc/host/mvsdio.c
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@@ -111,10 +111,15 @@ static int mvsd_setup_data(struct mvsd_host *host, struct mmc_data *data)
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mvsd_write(MVSD_BLK_COUNT, data->blocks);
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mvsd_write(MVSD_BLK_SIZE, data->blksz);
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- if (nodma || (data->blksz | data->sg->offset) & 3) {
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+ if (nodma || (data->blksz | data->sg->offset) & 3 ||
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+ ((!(data->flags & MMC_DATA_READ) && data->sg->offset & 0x3f))) {
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/*
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* We cannot do DMA on a buffer which offset or size
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* is not aligned on a 4-byte boundary.
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+ *
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+ * It also appears the host to card DMA can corrupt
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+ * data when the buffer is not aligned on a 64 byte
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+ * boundary.
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*/
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host->pio_size = data->blocks * data->blksz;
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host->pio_ptr = sg_virt(data->sg);
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--
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2.1.3
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