On Fri, Feb 10, 2017 at 06:46:45AM -0800, jiada_wang@xxxxxxxxxx wrote:
> From: Jiada Wang <jiada_wang@xxxxxxxxxx>
>
> sdma_disable_channel() cannot ensure dma is stopped to access
> module's FIFOs. Maybe SDMA core is running and accessing BD when
> disable of corresponding channel, this may cause sometimes even
> after call of .sdma_disable_channel(), SDMA core still be running
> and accessing module's FIFOs.
>
> We should add delay of one BD SDMA cost time, the maximum is 1ms.
> So that SDMA clients by calling .device_terminate_all can
> ensure SDMA core has really been stopped.
>
> Signed-off-by: Jiada Wang <jiada_wang@xxxxxxxxxx>
> ---
> drivers/dma/imx-sdma.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> index d1651a5..7332c40 100644
> --- a/drivers/dma/imx-sdma.c
> +++ b/drivers/dma/imx-sdma.c
> @@ -937,6 +937,14 @@ static int sdma_disable_channel(struct dma_chan *chan)
> return 0;
> }
>
> +static int sdma_disable_channel_with_delay(struct dma_chan *chan)
> +{
> + sdma_disable_channel(chan);
> + mdelay(1);
what is the gaurantee that 1ms is fine? Shouldn't you poll the bit to see
channel is disabled properly..
> +
> + return 0;
> +}
> +
> static void sdma_set_watermarklevel_for_p2p(struct sdma_channel *sdmac)
> {
> struct sdma_engine *sdma = sdmac->sdma;
> @@ -1828,7 +1836,7 @@ static int sdma_probe(struct platform_device *pdev)
> sdma->dma_device.device_prep_slave_sg = sdma_prep_slave_sg;
> sdma->dma_device.device_prep_dma_cyclic = sdma_prep_dma_cyclic;
> sdma->dma_device.device_config = sdma_config;
> - sdma->dma_device.device_terminate_all = sdma_disable_channel;
> + sdma->dma_device.device_terminate_all = sdma_disable_channel_with_delay;
> sdma->dma_device.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
> sdma->dma_device.dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
> sdma->dma_device.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
> --
> 2.7.4
>
>
--
~Vinod
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