diff options
| author | Geert Uytterhoeven <geert+renesas@glider.be> | 2014-07-09 12:26:23 +0200 |
|---|---|---|
| committer | Mark Brown <broonie@linaro.org> | 2014-07-16 22:41:51 +0100 |
| commit | 279d2378c9c4f05bbe41b55625b4003871026266 (patch) | |
| tree | c07d111eb25b18e62addcd98e311013c8c0e486b /drivers/spi/spi-sh-msiof.c | |
| parent | 51fd509046f71471e606f3fd76411d238c3b5d39 (diff) | |
| download | lwn-279d2378c9c4f05bbe41b55625b4003871026266.tar.gz lwn-279d2378c9c4f05bbe41b55625b4003871026266.zip | |
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>
Diffstat (limited to 'drivers/spi/spi-sh-msiof.c')
| -rw-r--r-- | drivers/spi/spi-sh-msiof.c | 23 |
1 files changed, 15 insertions, 8 deletions
diff --git a/drivers/spi/spi-sh-msiof.c b/drivers/spi/spi-sh-msiof.c index 9922ed3a4441..373de70baf08 100644 --- a/drivers/spi/spi-sh-msiof.c +++ b/drivers/spi/spi-sh-msiof.c @@ -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; |