sdmmc_host: add support for SET_BLOCK_COUNT (CMD23)

According to commit 7327d9fb6c ("Implement set block count
(CMD23) for x1000 target") some cards may experience data
corruption with certain controllers when CMD12 is used to
terminate multiblock writes. Using set block count (CMD23)
is reported to fix this issue.

Following the approach in that patch, use the SCR register
to probe support for CMD23, but disable use at runtime if
CMD23 generates an illegal command error.

Change-Id: I3ee1e48939b79b848fbda12c6737f2f974f47fa0

firmware/drivers/sdmmc_host.c

@@ -196,6 +196,7 @@ static void sdmmc_host_bus_reset(struct sdmmc_host *host)
     host->need_reset = false;
     host->initialized = false;
     host->is_hcs_card = false;
+    host->use_cmd23 = false;
     memset(&host->cardinfo, 0, sizeof(host->cardinfo));
 }
 
@@ -487,6 +488,10 @@ static int sdmmc_host_cmd_send_scr(struct sdmmc_host *host)
     host->cardinfo.scr[0] = load_be32_aligned(cmd.buffer + 4);
     host->cardinfo.scr[1] = load_be32_aligned(cmd.buffer + 0);
 
+    /* Use CMD23 (SET_BLOCK_COUNT) if card reports support */
+    if (host->cardinfo.scr[1] & 0x2)
+        host->use_cmd23 = true;
+
     return rc;
 }
 
@@ -562,6 +567,28 @@ static int sdmmc_host_cmd_set_block_len(struct sdmmc_host *host, int len)
     return sdmmc_host_submit_cmd(host, &cmd, NULL);
 }
 
+static int sdmmc_host_cmd_set_block_count(struct sdmmc_host *host, int count)
+{
+    struct sdmmc_host_response resp;
+    struct sdmmc_host_command cmd = {
+        .command   = SD_SET_BLOCK_COUNT,
+        .argument  = count,
+        .flags     = SDMMC_RESP_SHORT,
+    };
+
+    int rc = sdmmc_host_submit_cmd(host, &cmd, &resp);
+    if (rc)
+        return rc;
+
+    if (resp.data[0] & SD_R1_ILLEGAL_COMMAND)
+    {
+        logf("sdmmc: card claimed support for CMD23 but rejected it");
+        host->use_cmd23 = false;
+    }
+
+    return rc;
+}
+
 static void sdmmc_host_set_controller_bus_width(struct sdmmc_host *host, uint32_t width)
 {
     if (host->ops->set_bus_width)
@@ -764,6 +791,18 @@ static int sdmmc_host_transfer(struct sdmmc_host *host,
                 cmd.command = SD_WRITE_MULTIPLE_BLOCK;
             else
                 cmd.command = SD_READ_MULTIPLE_BLOCK;
+
+            /*
+             * Note: if the card rejects the command the return code
+             * will be successful, but use_cmd23 is set to false, and
+             * CMD12 will be used to terminate the read/write instead.
+             */
+            if (host->use_cmd23)
+            {
+                rc = sdmmc_host_cmd_set_block_count(host, xfer_count);
+                if (rc)
+                    goto out;
+            }
         }
         else
         {
@@ -787,7 +826,7 @@ static int sdmmc_host_transfer(struct sdmmc_host *host,
          *       the end of a transfer, eg. X1000; it might be worth
          *       supporting that via a feature flag.
          */
-        if (xfer_count > 1)
+        if (xfer_count > 1 && !host->use_cmd23)
         {
             memset(&cmd, 0, sizeof(cmd));
             cmd.command = SD_STOP_TRANSMISSION;

firmware/export/sdmmc_host.h

@@ -241,6 +241,7 @@ struct sdmmc_host
     bool powered     : 1;
     bool initialized : 1;
     bool is_hcs_card : 1;
+    bool use_cmd23   : 1;
 
     /* Controller implemented by the target */
     const struct sdmmc_controller_ops *ops;