stm32h7: sdmmc: handle CMD12 before second cache discard

commit 11817f99f80492ae9990e625828d7a161aea9928
Author: Aidan MacDonald <[email protected]>
Date:   Fri Aug 14 20:30:05 2026 +0100

    stm32h7: sdmmc: handle CMD12 before second cache discard
    
    Because DMA is still running until CMD12 is issued the second
    cache discard must occur after CMD12, otherwise the cache may
    contain a stale copy of data. While the buffer is garbage at
    this point it's probably not a good idea to leave the buffer
    in a weird state where the cache doesn't match what's in RAM.
    
    Change-Id: I7caf91d17631c92686ef0ad6f148e6c1d1bcbfa0

diff --git a/firmware/target/arm/stm32/sdmmc-stm32h7.c b/firmware/target/arm/stm32/sdmmc-stm32h7.c
index 13fd606eb4..ed93f229df 100644
--- a/firmware/target/arm/stm32/sdmmc-stm32h7.c
+++ b/firmware/target/arm/stm32/sdmmc-stm32h7.c
@@ -378,16 +378,8 @@ int stm32h7_sdmmc_submit_command(void *controller,
     /* Wait for command completion */
     semaphore_wait(&ctl->sem, TIMEOUT_BLOCK);
 
-    /*
-     * Discard data from speculative reads that may have
-     * accessed the buffer during the DMA transfer.
-     */
+    /* Save original command status code */
     int cmd_error = ctl->cmd_error;
-    if (cmd_error == SDMMC_STATUS_OK)
-    {
-        if (SDMMC_DATA_DIR(cmd->flags) == SDMMC_DATA_READ)
-            discard_dcache_range(buff_addr, buff_size);
-    }
 
     /*
      * If a data transfer command fails we need to issue CMD12
@@ -409,6 +401,15 @@ int stm32h7_sdmmc_submit_command(void *controller,
         stm32h7_sdmmc_submit_command(ctl, &cmd12, NULL);
     }
 
+    /*
+     * Discard data from speculative reads that may have
+     * accessed the buffer during the DMA transfer. Must
+     * be done after the CMD12 above otherwise the cache
+     * may end up out of sync with main memory.
+     */
+    if (SDMMC_DATA_DIR(cmd->flags) == SDMMC_DATA_READ)
+        discard_dcache_range(buff_addr, buff_size);
+
     /* Return error from original command */
     return cmd_error;
 }
-- 
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