linux-kernel - [PATCH 5.4 098/109] mmc: meson-gx: limit segments to 1 when dram-access-quirk is needed

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Message-Id: <20200714184110.256716835@linuxfoundation.org>
Date:   Tue, 14 Jul 2020 20:44:41 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Art Nikpal <art@...das.com>,
        Christian Hewitt <christianshewitt@...il.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: [PATCH 5.4 098/109] mmc: meson-gx: limit segments to 1 when dram-access-quirk is needed

From: Neil Armstrong <narmstrong@...libre.com>

commit 27a5e7d36d383970affae801d77141deafd536a8 upstream.

The actual max_segs computation leads to failure while using the broadcom
sdio brcmfmac/bcmsdh driver, since the driver tries to make usage of
scatter gather.

But with the dram-access-quirk we use a 1,5K SRAM bounce buffer, and the
max_segs current value of 3 leads to max transfers to 4,5k, which doesn't
work.

This patch sets max_segs to 1 to better describe the hardware limitation,
and fix the SDIO functionality with the brcmfmac/bcmsdh driver on Amlogic
G12A/G12B SoCs on boards like SEI510 or Khadas VIM3.

Reported-by: Art Nikpal <art@...das.com>
Reported-by: Christian Hewitt <christianshewitt@...il.com>
Fixes: acdc8e71d9bb ("mmc: meson-gx: add dram-access-quirk")
Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
Reviewed-by: Kevin Hilman <khilman@...libre.com>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/r/20200608084458.32014-1-narmstrong@baylibre.com
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/mmc/host/meson-gx-mmc.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/mmc/host/meson-gx-mmc.c
+++ b/drivers/mmc/host/meson-gx-mmc.c
@@ -1151,9 +1151,11 @@ static int meson_mmc_probe(struct platfo
 
 	mmc->caps |= MMC_CAP_CMD23;
 	if (host->dram_access_quirk) {
+		/* Limit segments to 1 due to low available sram memory */
+		mmc->max_segs = 1;
 		/* Limit to the available sram memory */
-		mmc->max_segs = SD_EMMC_SRAM_DATA_BUF_LEN / mmc->max_blk_size;
-		mmc->max_blk_count = mmc->max_segs;
+		mmc->max_blk_count = SD_EMMC_SRAM_DATA_BUF_LEN /
+				     mmc->max_blk_size;
 	} else {
 		mmc->max_blk_count = CMD_CFG_LENGTH_MASK;
 		mmc->max_segs = SD_EMMC_DESC_BUF_LEN /