mfd: rtsx: Do retry when DMA transfer error

The request should be resent when DMA transfer error occurred.
For rts5227, the clock rate needs to be reduced when error occurred.

Signed-off-by: Steven Feng <steven_feng@realsil.com.cn>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/rtsx_pcr.c b/drivers/mfd/rtsx_pcr.c
index 850590a..a0ac89d 100644
--- a/drivers/mfd/rtsx_pcr.c
+++ b/drivers/mfd/rtsx_pcr.c
@@ -30,6 +30,7 @@
 #include <linux/platform_device.h>
 #include <linux/mfd/core.h>
 #include <linux/mfd/rtsx_pci.h>
+#include <linux/mmc/card.h>
 #include <asm/unaligned.h>
 
 #include "rtsx_pcr.h"
@@ -452,8 +453,12 @@
 	}
 
 	spin_lock_irqsave(&pcr->lock, flags);
-	if (pcr->trans_result == TRANS_RESULT_FAIL)
-		err = -EINVAL;
+	if (pcr->trans_result == TRANS_RESULT_FAIL) {
+		err = -EILSEQ;
+		if (pcr->dma_error_count < RTS_MAX_TIMES_FREQ_REDUCTION)
+			pcr->dma_error_count++;
+	}
+
 	else if (pcr->trans_result == TRANS_NO_DEVICE)
 		err = -ENODEV;
 	spin_unlock_irqrestore(&pcr->lock, flags);
@@ -659,6 +664,13 @@
 	if (err < 0)
 		return err;
 
+	/* Reduce card clock by 20MHz each time a DMA transfer error occurs */
+	if (card_clock == UHS_SDR104_MAX_DTR &&
+	    pcr->dma_error_count &&
+	    PCI_PID(pcr) == RTS5227_DEVICE_ID)
+		card_clock = UHS_SDR104_MAX_DTR -
+			(pcr->dma_error_count * 20000000);
+
 	card_clock /= 1000000;
 	pcr_dbg(pcr, "Switch card clock to %dMHz\n", card_clock);
 
@@ -894,6 +906,7 @@
 			pcr->card_removed |= SD_EXIST;
 			pcr->card_inserted &= ~SD_EXIST;
 		}
+		pcr->dma_error_count = 0;
 	}
 
 	if (int_reg & MS_INT) {