[v2,10/25] hw/sd: ssi-sd: Support multiple block read

Commit Message

Bin Meng Jan. 23, 2021, 10:40 a.m. UTC

From: Bin Meng <[e-mail]>

In the case of a multiple block read operation every transferred
block has its suffix of CRC16. Update the state machine logic to
handle multiple block read.

Signed-off-by: Bin Meng <[e-mail]>
Acked-by: Alistair Francis <[e-mail]>

---

Changes in v2:
- Fix 2 typos in the commit message
- Add a comment block to explain the CMD12 timing
- Catch CMD12 in all of the data read states per the timing requirement

 hw/sd/ssi-sd.c | 38 +++++++++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 7 deletions(-)

Patch

diff --git a/hw/sd/ssi-sd.c b/hw/sd/ssi-sd.c
index 9e2f13374a..c1532b004b 100644
--- a/hw/sd/ssi-sd.c
+++ b/hw/sd/ssi-sd.c
@@ -52,6 +52,7 @@  struct ssi_sd_state {
     uint8_t cmdarg[4];
     uint8_t response[5];
     uint16_t crc16;
+    int32_t read_bytes;
     int32_t arglen;
     int32_t response_pos;
     int32_t stopping;
@@ -82,11 +83,26 @@  static uint32_t ssi_sd_transfer(SSIPeripheral *dev, uint32_t val)
 {
     ssi_sd_state *s = SSI_SD(dev);
 
-    /* Special case: allow CMD12 (STOP TRANSMISSION) while reading data.  */
-    if (s->mode == SSI_SD_DATA_READ && val == 0x4c) {
-        s->mode = SSI_SD_CMD;
-        /* There must be at least one byte delay before the card responds.  */
-        s->stopping = 1;
+    /*
+     * Special case: allow CMD12 (STOP TRANSMISSION) while reading data.
+     *
+     * See "Physical Layer Specification Version 8.00" chapter 7.5.2.2,
+     * to avoid conflict between CMD12 response and next data block,
+     * timing of CMD12 should be controlled as follows:
+     *
+     * - CMD12 issued at the timing that end bit of CMD12 and end bit of
+     *   data block is overlapped
+     * - CMD12 issued after one clock cycle after host receives a token
+     *   (either Start Block token or Data Error token)
+     *
+     * We need to catch CMD12 in all of the data read states.
+     */
+    if (s->mode >= SSI_SD_PREP_DATA && s->mode <= SSI_SD_DATA_CRC16) {
+        if (val == 0x4c) {
+            s->mode = SSI_SD_CMD;
+            /* There must be at least one byte delay before the card responds */
+            s->stopping = 1;
+        }
     }
 
     switch (s->mode) {
@@ -206,8 +222,9 @@  static uint32_t ssi_sd_transfer(SSIPeripheral *dev, uint32_t val)
         return 0xfe;
     case SSI_SD_DATA_READ:
         val = sdbus_read_byte(&s->sdbus);
+        s->read_bytes++;
         s->crc16 = crc_ccitt_false(s->crc16, (uint8_t *)&val, 1);
-        if (!sdbus_data_ready(&s->sdbus)) {
+        if (!sdbus_data_ready(&s->sdbus) || s->read_bytes == 512) {
             DPRINTF("Data read end\n");
             s->mode = SSI_SD_DATA_CRC16;
         }
@@ -218,7 +235,12 @@  static uint32_t ssi_sd_transfer(SSIPeripheral *dev, uint32_t val)
         s->response_pos++;
         if (s->response_pos == 2) {
             DPRINTF("CRC16 read end\n");
-            s->mode = SSI_SD_CMD;
+            if (s->read_bytes == 512 && s->cmd != 17) {
+                s->mode = SSI_SD_PREP_DATA;
+            } else {
+                s->mode = SSI_SD_CMD;
+            }
+            s->read_bytes = 0;
             s->response_pos = 0;
         }
         return val;
@@ -258,6 +280,7 @@  static const VMStateDescription vmstate_ssi_sd = {
         VMSTATE_UINT8_ARRAY(cmdarg, ssi_sd_state, 4),
         VMSTATE_UINT8_ARRAY(response, ssi_sd_state, 5),
         VMSTATE_UINT16(crc16, ssi_sd_state),
+        VMSTATE_INT32(read_bytes, ssi_sd_state),
         VMSTATE_INT32(arglen, ssi_sd_state),
         VMSTATE_INT32(response_pos, ssi_sd_state),
         VMSTATE_INT32(stopping, ssi_sd_state),
@@ -310,6 +333,7 @@  static void ssi_sd_reset(DeviceState *dev)
     memset(s->cmdarg, 0, sizeof(s->cmdarg));
     memset(s->response, 0, sizeof(s->response));
     s->crc16 = 0;
+    s->read_bytes = 0;
     s->arglen = 0;
     s->response_pos = 0;
     s->stopping = 0;