[PATCH v3] mmc: meson-gx: fix SDIO interrupt handling

[Peter Suti]

With the interrupt support introduced in commit 066ecde sometimes the
Marvell-8987 wifi chip got stuck using the marvell-sd-uapsta-8987
vendor driver. The cause seems to be that after sending ack to all interrupts
the IRQ_SDIO still happens, but it is ignored.

To work around this, recheck the IRQ_SDIO after meson_mmc_request_done().

Inspired by 9e2582e ("mmc: mediatek: fix SDIO irq issue") which used a
similar fix to handle lost interrupts.

Fixes: 066ecde ("mmc: meson-gx: add SDIO interrupt support")

Signed-off-by: Peter Suti <peter.suti at streamunlimited.com>
---
Changes in v2:
	- use spin_lock instead of spin_lock_irqsave
	- only reenable interrupts if they were enabled already

Changes in v3:
	- Rework the patch based on feedback from Heiner Kallweit.
		The IRQ does not happen on 2 CPUs and the hard IRQ is not re-entrant.
		But still one SDIO IRQ is lost without this change.
		After the ack, reading the SD_EMMC_STATUS BIT(15) is set, but 
		meson_mmc_irq() is never called again.

		The fix is similar to Mediatek msdc_recheck_sdio_irq().
		That platform also loses an IRQ in some cases it seems.

 drivers/mmc/host/meson-gx-mmc.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
index 6e5ea0213b47..7d3ee2f9a7f6 100644
--- a/drivers/mmc/host/meson-gx-mmc.c
+++ b/drivers/mmc/host/meson-gx-mmc.c
@@ -1023,6 +1023,22 @@ static irqreturn_t meson_mmc_irq(int irq, void *dev_id)
 	if (ret == IRQ_HANDLED)
 		meson_mmc_request_done(host->mmc, cmd->mrq);
 
+	/*
+	* Sometimes after we ack all raised interrupts,
+	* an IRQ_SDIO can still be pending, which can get lost.
+	*
+	* To prevent this, recheck the IRQ_SDIO here and schedule
+	* it to be processed.
+	*/
+	raw_status = readl(host->regs + SD_EMMC_STATUS);
+	status = raw_status & (IRQ_EN_MASK | IRQ_SDIO);
+	if (status & IRQ_SDIO) {
+		spin_lock(&host->lock);
+		__meson_mmc_enable_sdio_irq(host->mmc, 0);
+		sdio_signal_irq(host->mmc);
+		spin_unlock(&host->lock);
+	}
+
 	return ret;
 }
 
-- 
2.25.1