spi: sh-msiof: Handle dmaengine_prep_slave_single() failures gracefully
As typically a shmobile SoC has less DMA channels than devices that can use
DMA, we may want to prioritize access to the DMA channels in the future.
This means that dmaengine_prep_slave_single() may start failing
arbitrarily.
Handle dmaengine_prep_slave_single() failures gracefully by falling back to
PIO. This requires moving DMA-specific configuration of the MSIOF device
after the call(s) to dmaengine_prep_slave_single().
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/drivers/spi/spi-sh-msiof.c b/drivers/spi/spi-sh-msiof.c
index 9922ed3..373de70 100644
--- a/drivers/spi/spi-sh-msiof.c
+++ b/drivers/spi/spi-sh-msiof.c
@@ -636,12 +636,6 @@
dma_cookie_t cookie;
int ret;
- /* 1 stage FIFO watermarks for DMA */
- sh_msiof_write(p, FCTR, FCTR_TFWM_1 | FCTR_RFWM_1);
-
- /* setup msiof transfer mode registers (32-bit words) */
- sh_msiof_spi_set_mode_regs(p, tx, rx, 32, len / 4);
-
if (tx) {
ier_bits |= IER_TDREQE | IER_TDMAE;
dma_sync_single_for_device(&p->pdev->dev, p->tx_dma_addr, len,
@@ -650,7 +644,7 @@
p->tx_dma_addr, len, DMA_TO_DEVICE,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (!desc_tx)
- return -EIO;
+ return -EAGAIN;
}
if (rx) {
@@ -659,8 +653,15 @@
p->rx_dma_addr, len, DMA_FROM_DEVICE,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (!desc_rx)
- return -EIO;
+ return -EAGAIN;
}
+
+ /* 1 stage FIFO watermarks for DMA */
+ sh_msiof_write(p, FCTR, FCTR_TFWM_1 | FCTR_RFWM_1);
+
+ /* setup msiof transfer mode registers (32-bit words) */
+ sh_msiof_spi_set_mode_regs(p, tx, rx, 32, len / 4);
+
sh_msiof_write(p, IER, ier_bits);
reinit_completion(&p->done);
@@ -822,6 +823,12 @@
copy32(p->tx_dma_page, tx_buf, l / 4);
ret = sh_msiof_dma_once(p, tx_buf, rx_buf, l);
+ if (ret == -EAGAIN) {
+ pr_warn_once("%s %s: DMA not available, falling back to PIO\n",
+ dev_driver_string(&p->pdev->dev),
+ dev_name(&p->pdev->dev));
+ break;
+ }
if (ret)
return ret;