[RFC.PATCH v1 2/2] sd:sdhci: Fix data transfer did not complete if data size is bigger then SDMA Buffer Boundary

[Jamin Lin]

According to the design of sdhci_sdma_transfer_multi_blocks, if the
"s->blkcnt * 512" was bigger than the SDMA Buffer boundary, it breaked the
while loop of data transfer and set SDHC_NISEN_DMA in the normal interreupt
status to notify the firmware that this SDMA boundary buffer Transfer Complete
and firmware should set the system address of the next SDMA boundary buffer
for the remaining data transfer.

However, after firmware set the system address of the next SDMA boundary buffer
in the SDMA System Address Register(0x00), SDHCI modle did not start the data
transfer, again. Finally, firmware breaked the data transfer because firmware
did not receive the DMA Interrupt and Tansfer Complete Interrupt from SDHCI
model.

Error log from u-boot
```
sdhci_transfer_data: Transfer data timeout
 ** fs_devread read error - block
```

According to the following mention from SDMA System Address Refister of SDHCI
spec,
'''
This register contains the system memory address for an SDMA transfer in
32-bit addressing mode. When the Host Controller stops an SDMA transfer,
this register shall point to the system address of the next contiguous data
position.
It can be accessed only if no transaction is executing (i.e., after a 
transaction
has stopped). Reading this register during SDMA transfers may return an
invalid value.
The Host Driver shall initialize this register before starting an SDMA
transaction.
After SDMA has stopped, the next system address of the next contiguous
data position can be read from this register.
The SDMA transfer waits at the every boundary specified by the SDMA
Buffer Boundary in the Block Size register. The Host Controller generates
DMA Interrupt to request the Host Driver to update this register. The Host
Driver sets the next system address of the next data position to this register.
When the most upper byte of this register (003h) is written, the Host Controller
restarts the SDMA transfer.
''',

restrat the data transfer if firmware set the SDMA System Address, s->blkcnt
is bigger than 0 and SDHCI is in the data transfer state.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
---
 hw/sd/sdhci.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/hw/sd/sdhci.c b/hw/sd/sdhci.c
index 47d96b935b..53c23c5437 100644
--- a/hw/sd/sdhci.c
+++ b/hw/sd/sdhci.c
@@ -1170,6 +1170,15 @@ sdhci_write(void *opaque, hwaddr offset, uint64_t val, 
unsigned size)
                     sdhci_sdma_transfer_single_block(s);
                 }
             }
+        } else if (TRANSFERRING_DATA(s->prnsts)) {
+            /* restarts the SDMA transfer if blkcnt is not zero  */
+            if (s->blkcnt && SDHC_DMA_TYPE(s->hostctl1) == SDHC_CTRL_SDMA) {
+                if (s->trnmod & SDHC_TRNS_MULTI) {
+                    sdhci_sdma_transfer_multi_blocks(s);
+                } else {
+                    sdhci_sdma_transfer_single_block(s);
+                }
+            }
         }
         break;
     case SDHC_BLKSIZE:
-- 
2.34.1