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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>
This commit is contained in:
Geert Uytterhoeven 2014-07-09 12:26:23 +02:00 committed by Mark Brown
parent 51fd509046
commit 279d2378c9
1 changed files with 15 additions and 8 deletions
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23
drivers/spi/spi-sh-msiof.c
View File

@ -636,12 +636,6 @@ static int sh_msiof_dma_once(struct sh_msiof_spi_priv *p, const void *tx,
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 @@ static int sh_msiof_dma_once(struct sh_msiof_spi_priv *p, const void *tx,
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 @@ static int sh_msiof_dma_once(struct sh_msiof_spi_priv *p, const void *tx,
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 @@ static int sh_msiof_transfer_one(struct spi_master *master,
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;