mmc: meson-gx: limit segments to 1 when dram-access-quirk is needed

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@khadas.com>
Reported-by: Christian Hewitt <christianshewitt@gmail.com>
Fixes: acdc8e71d9bb ("mmc: meson-gx: add dram-access-quirk")
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200608084458.32014-1-narmstrong@baylibre.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
index 7eb38d7482c6d97d6ef16024a13759ac7af1c635..08a3b1c05acb9741c422553c446df5eda9e76fa9 100644 (file)
--- a/drivers/mmc/host/meson-gx-mmc.c
+++ b/drivers/mmc/host/meson-gx-mmc.c
@@ -1146,9 +1146,11 @@ static int meson_mmc_probe(struct platform_device *pdev)
 
        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 /