[incubator-nuttx] branch master updated: stm32f7:sdmmc invalidate before DMA to avoid eviction overwrite

[xi...@apache.org]

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xiaoxiang pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/incubator-nuttx.git


The following commit(s) were added to refs/heads/master by this push:
     new 74e692b  stm32f7:sdmmc invalidate before DMA to avoid eviction overwrite
74e692b is described below

commit 74e692b3c12836a8297e09b9f22c91b7469fe0ac
Author: David Sidrane <Da...@NscDg.com>
AuthorDate: Wed Dec 15 11:25:15 2021 -0800

    stm32f7:sdmmc invalidate before DMA to avoid eviction overwrite
    
      For FAT the same buffer is used for read and writes, there
      is a possibility a cache line is dirty. But the fs is
      not dirty and will not write the sector to disk. This can
      be seen  https://github.com/PX4/NuttX/pull/175
    
      When the system is busy that cache line can be evicted after the
      RX DMA has completed and overwrite the data in memory. The solution
      is to invalidate before the DMA to prevent an evection causing an
      overwite, and after the DMA it to insure coherency.
---
 arch/arm/src/stm32f7/stm32_sdmmc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/src/stm32f7/stm32_sdmmc.c b/arch/arm/src/stm32f7/stm32_sdmmc.c
index 0d7968c..0350c17 100644
--- a/arch/arm/src/stm32f7/stm32_sdmmc.c
+++ b/arch/arm/src/stm32f7/stm32_sdmmc.c
@@ -3115,6 +3115,8 @@ static int stm32_dmarecvsetup(FAR struct sdio_dev_s *dev,
     {
       priv->rxbuffer = buffer;
       priv->rxend    = buffer + buflen;
+      up_invalidate_dcache((uintptr_t)priv->rxbuffer,
+                           (uintptr_t)priv->rxend);
     }
 
   /* Start the DMA */