mmc: sdio: add a quirk for broken SDIO_CCCR_INTx polling

Polling SDIO_CCCR_INTx could create a fake interrupt with Marvell
SD8797 card. Add a quirk to handle this case. The fixup here is
to issue a dummy CMD52 read to function 0 register 0xff, and this
dummy read must be right after SDIO_CCCR_INTx is read.

Patch has been verified on a dw_mmc controller (Samsung Chromebook)
with MMC_CAP_SDIO_IRQ disabled.

Signed-off-by: Bing Zhao <bzhao@marvell.com>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <chris@printf.net>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/mmc/core/sdio_irq.c b/drivers/mmc/core/sdio_irq.c
index 3d8ceb4084de..aaa90460ed23 100644
--- a/drivers/mmc/core/sdio_irq.c
+++ b/drivers/mmc/core/sdio_irq.c
@@ -53,6 +53,17 @@ static int process_sdio_pending_irqs(struct mmc_host *host)
                 return ret;
         }
 
+        if (pending && mmc_card_broken_irq_polling(card) &&
+            !(host->caps & MMC_CAP_SDIO_IRQ)) {
+                unsigned char dummy;
+
+                /* A fake interrupt could be created when we poll SDIO_CCCR_INTx
+                 * register with a Marvell SD8797 card. A dummy CMD52 read to
+                 * function 0 register 0xff can avoid this.
+                 */
+                mmc_io_rw_direct(card, 0, 0, 0xff, 0, &dummy);
+        }
+
         count = 0;
         for (i = 1; i <= 7; i++) {
                 if (pending & (1 << i)) {