linux-kernel - [PATCH 2/2] mmc: meson-gx: also check SD_IO_RW

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Date:   Mon, 26 Apr 2021 19:55:59 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     ulf.hansson@...aro.org, khilman@...libre.com
Cc:     linux-mmc@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Neil Armstrong <narmstrong@...libre.com>,
        Christian Hewitt <christianshewitt@...il.com>
Subject: [PATCH 2/2] mmc: meson-gx: also check SD_IO_RW_EXTENDED for scatterlist size alignment

The brcmfmac driver can generate a scatterlist from a skb with each packets
not aligned to the block size. This is not supported by the Amlogic Descriptor
dma engine where each descriptor must match a multiple of the block size.

The sg list is valid, since the sum of the sg buffers is a multiple of the
block size, but we must discard those when in SD_IO_RW_EXTENDED mode since
SDIO block mode can be used under the hood even with data->blocks == 1.

Those transfers are very rare, thus can be replaced by a bounce buffer
without real performance loss.

Fixes: 7412dee9f1fd ("mmc: meson-gx: replace WARN_ONCE with dev_warn_once about scatterlist size alignment in block mode")
Reported-by: Christian Hewitt <christianshewitt@...il.com>
Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
---
 drivers/mmc/host/meson-gx-mmc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
index 1c61f0f24c09..016a6106151a 100644
--- a/drivers/mmc/host/meson-gx-mmc.c
+++ b/drivers/mmc/host/meson-gx-mmc.c
@@ -236,7 +236,8 @@ static void meson_mmc_get_transfer_mode(struct mmc_host *mmc,
 	if (host->dram_access_quirk)
 		return;
 
-	if (data->blocks > 1) {
+	/* SD_IO_RW_EXTENDED (CMD53) can also use block mode under the hood */
+	if (data->blocks > 1 || mrq->cmd->opcode == SD_IO_RW_EXTENDED) {
 		/*
 		 * In block mode DMA descriptor format, "length" field indicates
 		 * number of blocks and there is no way to pass DMA size that
-- 
2.25.1