Change the driver's default behaviour from DMA to PIO for each request.
Preparing DMA can fail or be prevented by other causes. Switch to a DMA
operation only, if it is really possible.
This avoids a NULL pointer dereference on shutdown in mxcmci_start_cmd()
where it tries to store a DMA callback configuration into mxcmci_host::desc
which isn't setup a this point of time.
Signed-off-by: Juergen Borleis <jbe@xxxxxxxxxxxxxx>
---
drivers/mmc/host/mxcmmc.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/drivers/mmc/host/mxcmmc.c b/drivers/mmc/host/mxcmmc.c
index 611f827..41feea9 100644
--- a/drivers/mmc/host/mxcmmc.c
+++ b/drivers/mmc/host/mxcmmc.c
@@ -293,14 +293,13 @@ static int mxcmci_setup_data(struct mxcmci_host *host, struct mmc_data *data)
mxcmci_writew(host, blksz, MMC_REG_BLK_LEN);
host->datasize = datasize;
- if (!mxcmci_use_dma(host))
- return 0;
+ if (host->dma == NULL)
+ return 0; /* Keep PIO */
+ /* Avoid the use of DMA on short transfers, e.g. non-sectors for example */
for_each_sg(data->sg, sg, data->sg_len, i) {
- if (sg->offset & 3 || sg->length & 3 || sg->length < 512) {
- host->do_dma = 0;
- return 0;
- }
+ if (sg->offset & 3 || sg->length & 3 || sg->length < 512)
+ return 0; /* Keep PIO */
}
if (data->flags & MMC_DATA_READ) {
@@ -325,9 +324,11 @@ static int mxcmci_setup_data(struct mxcmci_host *host, struct mmc_data *data)
if (!host->desc) {
dma_unmap_sg(host->dma->device->dev, data->sg, data->sg_len,
host->dma_dir);
- host->do_dma = 0;
- return 0; /* Fall back to PIO */
+ return 0; /* Keep PIO */
}
+
+ /* DMA is possible */
+ host->do_dma = 1;
wmb();
dmaengine_submit(host->desc);
@@ -747,8 +748,11 @@ static void mxcmci_request(struct mmc_host *mmc, struct mmc_request *req)
host->req = req;
host->cmdat &= ~CMD_DAT_CONT_INIT;
- if (host->dma)
- host->do_dma = 1;
+ /*
+ * Default always to PIO. DMA will be enabled in
+ * mxcmci_setup_data() if possible
+ */
+ host->do_dma = 0;
if (req->data) {
error = mxcmci_setup_data(host, req->data);
--
2.20.1
