mmc: mmci: Prevent polling for busy detection in IRQ context

The IRQ handler, mmci_irq(), loops until all status bits have been cleared.
However, the status bit signaling busy in variant->busy_detect_flag, may be
set even if busy detection isn't monitored for the current request.

This may be the case for the CMD11 when switching the I/O voltage, which
leads to that mmci_irq() busy loops in IRQ context. Fix this problem, by
clearing the status bit for busy, before continuing to validate the
condition for the loop. This is safe, because the busy status detection has
already been taken care of by mmci_cmd_irq().
Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/mmci.c

@@ -1535,9 +1535,10 @@ static irqreturn_t mmci_irq(int irq, void *dev_id)
 		}
 
 		/*
-		 * Don't poll for busy completion in irq context.
+		 * Busy detection has been handled by mmci_cmd_irq() above.
+		 * Clear the status bit to prevent polling in IRQ context.
 		 */
-		if (host->variant->busy_detect && host->busy_status)
+		if (host->variant->busy_detect_flag)
 			status &= ~host->variant->busy_detect_flag;
 
 		ret = 1;