Alignment of buffers in ff.h

[khevessy]

I am using FatFS library on STM32H723 MCU with FreeRTOS and DMA. I have encountered the issue mentioned here on the forum. When buffers are not aligned, file access functions like f_read return FR_INT_ERR as cache coherency operations probably don't work as expected. Turning the ENABLE_SCRATCH_BUFFER and ENABLE_SD_DMA_CACHE_MAINTENANCE defines on in sd_diskio.c template also does not help. I do not know if ST is able to fix those issues in the library, but the fix is simple, change

stm32_mw_fatfs/src/ff.h

Line 125 in 5042a94

BYTE win[_MAX_SS]; /* Disk access window for Directory, FAT (and file data at tiny cfg) */

to

BYTE win[_MAX_SS] __attribute__((aligned(32)));

and

stm32_mw_fatfs/src/ff.h

Line 170 in 5042a94

BYTE buf[_MAX_SS]; /* File private data read/write window */

to

BYTE buf[_MAX_SS] __attribute__((aligned(32)));.

Then the issue goes away completely.

[TOUNSTM]

Hello @khevessy,

Thank you for your contribution. You are absolutely right about this point.
Actually, the point you raised has already been dealt and fixed internally. The fix will be made available in the frame of a future release.

Thank you again for your contribution. We are looking forward to reading from you again.

With regards,

[TOUNSTM]

ST Internal Reference: 133958