sdmmc_host: support multiblock transfers

commit 6da20a18c3dc81d7ca2ae5462d2ed77b4ddd5617
Author: Aidan MacDonald <[email protected]>
Date:   Fri Feb 6 10:22:25 2026 +0000

    sdmmc_host: support multiblock transfers
    
    Change-Id: I6414028bbafd4ea4ef469f9a387f4bd52ec227e5

diff --git a/firmware/drivers/sdmmc_host.c b/firmware/drivers/sdmmc_host.c
index c012731a7e..ad21cfed32 100644
--- a/firmware/drivers/sdmmc_host.c
+++ b/firmware/drivers/sdmmc_host.c
@@ -677,10 +677,12 @@ static int sdmmc_host_transfer(struct sdmmc_host *host,
     if (start + count > host->cardinfo.numblocks)
         goto out;
 
+    int max_nr_blocks = MAX(host->config.max_nr_blocks, 1);
     while (count > 0)
     {
-        /* TODO: multiple block transfers */
-        int xfer_count = 1;
+        int xfer_count = count;
+        if (xfer_count > max_nr_blocks)
+            xfer_count = max_nr_blocks;
 
         /* Set block length for non-HCS cards */
         if (!host->is_hcs_card)
@@ -692,15 +694,25 @@ static int sdmmc_host_transfer(struct sdmmc_host *host,
 
         struct sdmmc_host_command cmd = {
             .buffer = buf,
-            .nr_blocks = 1,
+            .nr_blocks = xfer_count,
             .block_len = SD_BLOCK_SIZE,
             .flags = SDMMC_RESP_SHORT | data_dir,
         };
 
-        if (data_dir == SDMMC_DATA_WRITE)
-            cmd.command = SD_WRITE_BLOCK;
+        if (xfer_count > 1)
+        {
+            if (data_dir == SDMMC_DATA_WRITE)
+                cmd.command = SD_WRITE_MULTIPLE_BLOCK;
+            else
+                cmd.command = SD_READ_MULTIPLE_BLOCK;
+        }
         else
-            cmd.command = SD_READ_SINGLE_BLOCK;
+        {
+            if (data_dir == SDMMC_DATA_WRITE)
+                cmd.command = SD_WRITE_BLOCK;
+            else
+                cmd.command = SD_READ_SINGLE_BLOCK;
+        }
 
         if (host->cardinfo.sd2plus)
             cmd.argument = start;
@@ -711,6 +723,22 @@ static int sdmmc_host_transfer(struct sdmmc_host *host,
         if (rc)
             goto out;
 
+        /*
+         * NOTE: some controllers can send CMD12 automatically after
+         *       the end of a transfer, eg. X1000; it might be worth
+         *       supporting that via a feature flag.
+         */
+        if (xfer_count > 1)
+        {
+            memset(&cmd, 0, sizeof(cmd));
+            cmd.command = SD_STOP_TRANSMISSION;
+            cmd.flags = SDMMC_RESP_SHORT | SDMMC_RESP_BUSY;
+
+            rc = sdmmc_host_submit_cmd(host, &cmd, NULL);
+            if (rc)
+                goto out;
+        }
+
         buf += xfer_count * SD_BLOCK_SIZE;
         start += xfer_count;
         count -= xfer_count;
diff --git a/firmware/export/sdmmc_host.h b/firmware/export/sdmmc_host.h
index 1d00c94a27..3d6c7fbb0f 100644
--- a/firmware/export/sdmmc_host.h
+++ b/firmware/export/sdmmc_host.h
@@ -207,6 +207,9 @@ struct sdmmc_host_config
     uint32_t bus_widths;
     uint32_t bus_clocks;
 
+    /* Max number of blocks in a multiblock transfer */
+    int max_nr_blocks;
+
     /* Set to true if the device is removable at runtime */
     bool is_removable;
 };
-- 
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