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 <[email protected]> Acked-by: Laurent Pinchart <[email protected]> --- v2: - Add Acked-by --- drivers/spi/spi-sh-msiof.c | 23 +++++++++++++++-------- 1 file changed, 15 insertions(+), 8 deletions(-) diff --git a/drivers/spi/spi-sh-msiof.c b/drivers/spi/spi-sh-msiof.c index 6f449b24704a..2a4354dcd661 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->master->dma_tx->device->dev, @@ -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); @@ -823,6 +824,12 @@ 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; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
