[PATCH v4] mfd:rtsx: do retry when DMA transfer error

[steven_feng]

From: Steven Feng <steven_f...@realsil.com.cn>

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_f...@realsil.com.cn>
---
 drivers/mfd/rtsx_pcr.c       | 18 ++++++++++++++++--
 include/linux/mfd/rtsx_pci.h |  5 +++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/mfd/rtsx_pcr.c b/drivers/mfd/rtsx_pcr.c
index 98029ee..8e21fd6 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 @@ 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 +664,14 @@ int rtsx_pci_switch_clock(struct rtsx_pcr *pcr, unsigned 
int card_clock,
        if (err < 0)
                return err;
 
+       /* Reduce MMC 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 +907,7 @@ 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) {
diff --git a/include/linux/mfd/rtsx_pci.h b/include/linux/mfd/rtsx_pci.h
index 7eb7cba..116816f 100644
--- a/include/linux/mfd/rtsx_pci.h
+++ b/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))
-- 
1.9.1