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>

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 @@ int rtsx_pci_dma_transfer(struct rtsx_pcr *pcr, struct scatterlist *sglist,
 	}
 
 	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 @@ int rtsx_pci_switch_clock(struct rtsx_pcr *pcr, unsigned int card_clock,
 	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 @@ static irqreturn_t rtsx_pci_isr(int irq, void *dev_id)
 			pcr->card_removed |= SD_EXIST;
 			pcr->card_inserted &= ~SD_EXIST;
 		}
+		pcr->dma_error_count = 0;
 	}
 
 	if (int_reg & MS_INT) {

include/linux/mfd/rtsx_pci.h

@@ -850,6 +850,9 @@
 
 #define rtsx_pci_init_cmd(pcr)		((pcr)->ci = 0)
 
+#define RTS5227_DEVICE_ID		0x5227
+#define RTS_MAX_TIMES_FREQ_REDUCTION	8
+
 struct rtsx_pcr;
 
 struct pcr_handle {
@@ -957,6 +960,8 @@ struct rtsx_pcr {
 
 	int				num_slots;
 	struct rtsx_slot		*slots;
+
+	u8				dma_error_count;
 };
 
 #define CHK_PCI_PID(pcr, pid)		((pcr)->pci->device == (pid))