[PATCH v2 03/25] hw/sd: ssi-sd: Fix incorrect card response sequence

[Bin Meng <bmeng.cn@gmail.com>]

From: Bin Meng <bin.meng@windriver.com>

Per the "Physical Layer Specification Version 8.00" chapter 7.5.1,
"Command/Response", there is a minimum 8 clock cycles (Ncr) before
the card response shows up on the data out line. However current
implementation jumps directly to the sending response state after
all 6 bytes command is received, which is a spec violation.

Add a new state PREP_RESP in the ssi-sd state machine to handle it.

Fixes: 775616c3ae8c ("Partial SD card SPI mode support")
Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Pragnesh Patel <pragnesh.patel@sifive.com>
Tested-by: Pragnesh Patel <pragnesh.patel@sifive.com>

---

Changes in v2:
- Add a debug printf in the state handling codes

 hw/sd/ssi-sd.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/hw/sd/ssi-sd.c b/hw/sd/ssi-sd.c
index 9a75e0095c..043e270066 100644
--- a/hw/sd/ssi-sd.c
+++ b/hw/sd/ssi-sd.c
@@ -36,6 +36,7 @@ do { fprintf(stderr, "ssi_sd: error: " fmt , ## __VA_ARGS__);} while (0)
 typedef enum {
     SSI_SD_CMD = 0,
     SSI_SD_CMDARG,
+    SSI_SD_PREP_RESP,
     SSI_SD_RESPONSE,
     SSI_SD_DATA_START,
     SSI_SD_DATA_READ,
@@ -163,12 +164,16 @@ static uint32_t ssi_sd_transfer(SSIPeripheral *dev, uint32_t val)
                 s->response[1] = status;
                 DPRINTF("Card status 0x%02x\n", status);
             }
-            s->mode = SSI_SD_RESPONSE;
+            s->mode = SSI_SD_PREP_RESP;
             s->response_pos = 0;
         } else {
             s->cmdarg[s->arglen++] = val;
         }
         return 0xff;
+    case SSI_SD_PREP_RESP:
+        DPRINTF("Prepare card response (Ncr)\n");
+        s->mode = SSI_SD_RESPONSE;
+        return 0xff;
     case SSI_SD_RESPONSE:
         if (s->stopping) {
             s->stopping = 0;
-- 
2.25.1