Re: [PATCH] spi: omap2-mcspi: fix dma transfer for vmalloced buffer

[Akinobu Mita <akinobu.mita@xxxxxxxxx>]

2016-03-22 1:00 GMT+09:00 Akinobu Mita <akinobu.mita@xxxxxxxxx>:
> Currently omap2-mcspi cannot handle dma transfer for vmalloced buffer.
> I hit this problem when using mtdblock on spi-nor.
>
> This lets the SPI core handle the page mapping for dma transfer buffer.
>
> Signed-off-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
> Cc: Mark Brown <broonie@xxxxxxxxxx>
> ---
>  drivers/spi/spi-omap2-mcspi.c | 62 ++++++++++++-------------------------------
>  1 file changed, 17 insertions(+), 45 deletions(-)
>
> diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
> index 0caa3c8..43a02e3 100644
> --- a/drivers/spi/spi-omap2-mcspi.c
> +++ b/drivers/spi/spi-omap2-mcspi.c
> @@ -423,16 +423,12 @@ static void omap2_mcspi_tx_dma(struct spi_device *spi,
>
>         if (mcspi_dma->dma_tx) {
>                 struct dma_async_tx_descriptor *tx;
> -               struct scatterlist sg;
>
>                 dmaengine_slave_config(mcspi_dma->dma_tx, &cfg);
>
> -               sg_init_table(&sg, 1);
> -               sg_dma_address(&sg) = xfer->tx_dma;
> -               sg_dma_len(&sg) = xfer->len;
> -
> -               tx = dmaengine_prep_slave_sg(mcspi_dma->dma_tx, &sg, 1,
> -               DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> +               tx = dmaengine_prep_slave_sg(mcspi_dma->dma_tx, xfer->tx_sg.sgl,
> +                                            xfer->tx_sg.nents, DMA_MEM_TO_DEV,
> +                                            DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
>                 if (tx) {
>                         tx->callback = omap2_mcspi_tx_callback;
>                         tx->callback_param = spi;
> @@ -478,20 +474,15 @@ omap2_mcspi_rx_dma(struct spi_device *spi, struct spi_transfer *xfer,
>
>         if (mcspi_dma->dma_rx) {
>                 struct dma_async_tx_descriptor *tx;
> -               struct scatterlist sg;
>
>                 dmaengine_slave_config(mcspi_dma->dma_rx, &cfg);
>
>                 if ((l & OMAP2_MCSPI_CHCONF_TURBO) && mcspi->fifo_depth == 0)
>                         dma_count -= es;
>

The actual transfer length can be smaller than xfer->len by above line.
And the last word is filled after dma transfer completion.

So this patch is broken.  Could you revert remove this from your
development tree?
I don't find a way how to fix it without copy and pasting a lot of
line from spi core.

> -               sg_init_table(&sg, 1);
> -               sg_dma_address(&sg) = xfer->rx_dma;
> -               sg_dma_len(&sg) = dma_count;
> -
> -               tx = dmaengine_prep_slave_sg(mcspi_dma->dma_rx, &sg, 1,
> -                               DMA_DEV_TO_MEM, DMA_PREP_INTERRUPT |
> -                               DMA_CTRL_ACK);
> +               tx = dmaengine_prep_slave_sg(mcspi_dma->dma_rx, xfer->rx_sg.sgl,
> +                                            xfer->rx_sg.nents, DMA_DEV_TO_MEM,
> +                                            DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
>                 if (tx) {
>                         tx->callback = omap2_mcspi_rx_callback;
>                         tx->callback_param = spi;
> @@ -505,8 +496,6 @@ omap2_mcspi_rx_dma(struct spi_device *spi, struct spi_transfer *xfer,
>         omap2_mcspi_set_dma_req(spi, 1, 1);
>
>         wait_for_completion(&mcspi_dma->dma_rx_completion);
> -       dma_unmap_single(mcspi->dev, xfer->rx_dma, count,
> -                        DMA_FROM_DEVICE);
>
>         if (mcspi->fifo_depth > 0)
>                 return count;
> @@ -619,8 +608,6 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer)
>
>         if (tx != NULL) {
>                 wait_for_completion(&mcspi_dma->dma_tx_completion);
> -               dma_unmap_single(mcspi->dev, xfer->tx_dma, xfer->len,
> -                                DMA_TO_DEVICE);
>
>                 if (mcspi->fifo_depth > 0) {
>                         irqstat_reg = mcspi->base + OMAP2_MCSPI_IRQSTATUS;
> @@ -1087,6 +1074,16 @@ static void omap2_mcspi_cleanup(struct spi_device *spi)
>                 gpio_free(spi->cs_gpio);
>  }
>
> +static bool omap2_mcspi_can_dma(struct spi_master *master,
> +                               struct spi_device *spi,
> +                               struct spi_transfer *xfer)
> +{
> +       if (xfer->len < DMA_MIN_BYTES)
> +               return false;
> +
> +       return true;
> +}
> +
>  static int omap2_mcspi_work_one(struct omap2_mcspi *mcspi,
>                 struct spi_device *spi, struct spi_transfer *t)
>  {
> @@ -1268,32 +1265,6 @@ static int omap2_mcspi_transfer_one(struct spi_master *master,
>                 return -EINVAL;
>         }
>
> -       if (len < DMA_MIN_BYTES)
> -               goto skip_dma_map;
> -
> -       if (mcspi_dma->dma_tx && tx_buf != NULL) {
> -               t->tx_dma = dma_map_single(mcspi->dev, (void *) tx_buf,
> -                               len, DMA_TO_DEVICE);
> -               if (dma_mapping_error(mcspi->dev, t->tx_dma)) {
> -                       dev_dbg(mcspi->dev, "dma %cX %d bytes error\n",
> -                                       'T', len);
> -                       return -EINVAL;
> -               }
> -       }
> -       if (mcspi_dma->dma_rx && rx_buf != NULL) {
> -               t->rx_dma = dma_map_single(mcspi->dev, rx_buf, t->len,
> -                               DMA_FROM_DEVICE);
> -               if (dma_mapping_error(mcspi->dev, t->rx_dma)) {
> -                       dev_dbg(mcspi->dev, "dma %cX %d bytes error\n",
> -                                       'R', len);
> -                       if (tx_buf != NULL)
> -                               dma_unmap_single(mcspi->dev, t->tx_dma,
> -                                               len, DMA_TO_DEVICE);
> -                       return -EINVAL;
> -               }
> -       }
> -
> -skip_dma_map:
>         return omap2_mcspi_work_one(mcspi, spi, t);
>  }
>
> @@ -1377,6 +1348,7 @@ static int omap2_mcspi_probe(struct platform_device *pdev)
>         master->transfer_one = omap2_mcspi_transfer_one;
>         master->set_cs = omap2_mcspi_set_cs;
>         master->cleanup = omap2_mcspi_cleanup;
> +       master->can_dma = omap2_mcspi_can_dma;
>         master->dev.of_node = node;
>         master->max_speed_hz = OMAP2_MCSPI_MAX_FREQ;
>         master->min_speed_hz = OMAP2_MCSPI_MAX_FREQ >> 15;
> --
> 2.5.0
>
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