mmc: meson-gx: work around broken SDIO with certain WiFi chips

There have been reports about SDIO failing with certain WiFi chips in
descriptor chain mode. SD / eMMC are working fine.

So let's fall back to bounce buffer mode for command SD_IO_RW_EXTENDED.
This was reported to fix the error.

Fixes: 79ed05e329c3 "mmc: meson-gx: add support for descriptor chain mode"
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Tested-by: Martin Blumenstingl <martin.blumenstingl@googlemail.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 1842ed341af10e38902f1178f409d645b7301679..de962c2d5e000a834bc40064be3bbe426e55bf5a 100644 (file)
--- a/drivers/mmc/host/meson-gx-mmc.c
+++ b/drivers/mmc/host/meson-gx-mmc.c
@@ -210,6 +210,15 @@ static void meson_mmc_get_transfer_mode(struct mmc_host *mmc,
        int i;
        bool use_desc_chain_mode = true;
 
+       /*
+        * Broken SDIO with AP6255-based WiFi on Khadas VIM Pro has been
+        * reported. For some strange reason this occurs in descriptor
+        * chain mode only. So let's fall back to bounce buffer mode
+        * for command SD_IO_RW_EXTENDED.
+        */
+       if (mrq->cmd->opcode == SD_IO_RW_EXTENDED)
+               return;
+
        for_each_sg(data->sg, sg, data->sg_len, i)
                /* check for 8 byte alignment */
                if (sg->offset & 7) {