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 <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

drivers/mfd/rtsx_pcr.c

···
 #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"
···
 	}
 
 	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);
···
 			SD_CLK_DIVIDE_MASK, clk_divider);
 	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);
···
 			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

···
 
 #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 {
···
 
 	int				num_slots;
 	struct rtsx_slot		*slots;
+
+	u8				dma_error_count;
 };
 
 #define CHK_PCI_PID(pcr, pid)		((pcr)->pci->device == (pid))