[PATCH rtems-libbsd 2/2] st-sdmmc: Handle short not cache aligned buffers

[Christian Mauderer]

Possible data sources for SD driver:

- mmc_sd_switch():
    - length: 64 byte;
    - buffer on stack
- mmc_test_bus_width():
    - length: 4 or 8 byte
    - buffer in program memory or on stack
- mmc_app_send_scr():
    - length: 8 byte
    - buffer from device ivar structure
- mmc_app_sd_status():
    - length: 64 byte
    - buffer from device ivar structure
- mmc_send_ext_csd():
    - length: MMC_EXTCSD_SIZE = 512
    - buffer from device ivar structure
- rtems_bsd_mmcsd_disk_read_write():
    - length: depends on read
    - buffer from rtems_blkdev buffer -> already aligned
- mmcsd_ioctl_cmd():
    - length: depends on call
    - buffer malloced, not aligned -> patched in RTEMS

So the problematic buffers are only the ones up to 512 bytes. Copy these data
into a buffer to avoid that problem.
---
 rtemsbsd/sys/dev/mmc/st-sdmmc.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/rtemsbsd/sys/dev/mmc/st-sdmmc.c b/rtemsbsd/sys/dev/mmc/st-sdmmc.c
index e50b400a..4b202952 100644
--- a/rtemsbsd/sys/dev/mmc/st-sdmmc.c
+++ b/rtemsbsd/sys/dev/mmc/st-sdmmc.c
@@ -117,7 +117,8 @@ __FBSDID("$FreeBSD$");
 #define RES_IRQ_SDMMC 2
 #define RES_NR 3
 
-#define DMA_BUF_SIZE CPU_CACHE_LINE_BYTES
+/* Maximum non-aligned buffer is 512 byte from mmc_send_ext_csd() */
+#define DMA_BUF_SIZE 512
 
 #if 0
 #define debug_print(sc, lvl, ...) \
@@ -575,14 +576,19 @@ st_sdmmc_cmd_do(struct st_sdmmc_softc *sc, struct 
mmc_command *cmd)
 
                BSD_ASSERT(xferlen % (1 << blksize) == 0);
 
-               if (xferlen < CPU_CACHE_LINE_BYTES) {
+               data = cmd->data->data;
+               /*
+                * Check whether data have to be copied. Reason is either
+                * misaligned start address or misaligned length.
+                */
+               if (((uintptr_t)data % CPU_CACHE_LINE_BYTES != 0) ||
+                   (xferlen % CPU_CACHE_LINE_BYTES) != 0) {
+                       BSD_ASSERT(xferlen < DMA_BUF_SIZE);
                        if ((cmd->data->flags & MMC_DATA_READ) == 0) {
                                memcpy(sc->dmabuf, cmd->data->data, xferlen);
                        }
                        data = sc->dmabuf;
                        short_xfer = true;
-               } else {
-                       data = cmd->data->data;
                }
 
                dctrl |= blksize << SDMMC_DCTRL_DBLOCKSIZE_Pos;
-- 
2.26.2

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