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>
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@ -636,12 +636,6 @@ static int sh_msiof_dma_once(struct sh_msiof_spi_priv *p, const void *tx,
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dma_cookie_t cookie;
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int ret;
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/* 1 stage FIFO watermarks for DMA */
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sh_msiof_write(p, FCTR, FCTR_TFWM_1 | FCTR_RFWM_1);
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/* setup msiof transfer mode registers (32-bit words) */
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sh_msiof_spi_set_mode_regs(p, tx, rx, 32, len / 4);
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if (tx) {
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ier_bits |= IER_TDREQE | IER_TDMAE;
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dma_sync_single_for_device(&p->pdev->dev, p->tx_dma_addr, len,
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@ -650,7 +644,7 @@ static int sh_msiof_dma_once(struct sh_msiof_spi_priv *p, const void *tx,
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p->tx_dma_addr, len, DMA_TO_DEVICE,
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DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
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if (!desc_tx)
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return -EIO;
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return -EAGAIN;
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}
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if (rx) {
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@ -659,8 +653,15 @@ static int sh_msiof_dma_once(struct sh_msiof_spi_priv *p, const void *tx,
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p->rx_dma_addr, len, DMA_FROM_DEVICE,
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DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
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if (!desc_rx)
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return -EIO;
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return -EAGAIN;
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}
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/* 1 stage FIFO watermarks for DMA */
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sh_msiof_write(p, FCTR, FCTR_TFWM_1 | FCTR_RFWM_1);
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/* setup msiof transfer mode registers (32-bit words) */
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sh_msiof_spi_set_mode_regs(p, tx, rx, 32, len / 4);
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sh_msiof_write(p, IER, ier_bits);
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reinit_completion(&p->done);
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@ -822,6 +823,12 @@ static int sh_msiof_transfer_one(struct spi_master *master,
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copy32(p->tx_dma_page, tx_buf, l / 4);
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ret = sh_msiof_dma_once(p, tx_buf, rx_buf, l);
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if (ret == -EAGAIN) {
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pr_warn_once("%s %s: DMA not available, falling back to PIO\n",
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dev_driver_string(&p->pdev->dev),
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dev_name(&p->pdev->dev));
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break;
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}
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if (ret)
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return ret;
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