Re: [PATCH v2 03/19] spi: dw: Clear DMAC register when done or stopped

[Andy Shevchenko]

On Fri, May 15, 2020 at 01:47:42PM +0300, Serge Semin wrote:
> If DMAC register is left uncleared any further DMAless transfers
> may cause the DMAC hardware handshaking interface getting activated.
> So the next DMA-based Rx/Tx transaction will be started right
> after the dma_async_issue_pending() method is invoked even if no
> DMATDLR/DMARDLR conditions are met. This at the same time may cause
> the Tx/Rx FIFO buffers underrun/overrun. In order to fix this we
> must clear DMAC register after a current DMA-based transaction is
> finished.

After adding a Fixes tag,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>

> 
> Co-developed-by: Georgy Vlasov <Georgy.Vlasov@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Georgy Vlasov <Georgy.Vlasov@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx>
> Cc: Ramil Zaripov <Ramil.Zaripov@xxxxxxxxxxxxxxxxxxxx>
> Cc: Alexey Malahov <Alexey.Malahov@xxxxxxxxxxxxxxxxxxxx>
> Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
> Cc: Paul Burton <paulburton@xxxxxxxxxx>
> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Allison Randal <allison@xxxxxxxxxxx>
> Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> Cc: Gareth Williams <gareth.williams.jx@xxxxxxxxxxx>
> Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> Cc: linux-mips@xxxxxxxxxxxxxxx
> Cc: devicetree@xxxxxxxxxxxxxxx
> 
> ---
> 
> Changelog v2:
> - Move the patch to the head of the series so one could be picked up to
>   the stable kernels as a fix.
> - Clear the DMACR in the DMA exit callback too.
> ---
>  drivers/spi/spi-dw-mid.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/spi/spi-dw-mid.c b/drivers/spi/spi-dw-mid.c
> index 7a5ae1506365..0c597b6bb154 100644
> --- a/drivers/spi/spi-dw-mid.c
> +++ b/drivers/spi/spi-dw-mid.c
> @@ -108,6 +108,8 @@ static void mid_spi_dma_exit(struct dw_spi *dws)
>  		dmaengine_terminate_sync(dws->rxchan);
>  		dma_release_channel(dws->rxchan);
>  	}
> +
> +	dw_writel(dws, DW_SPI_DMACR, 0);
>  }
>  
>  static irqreturn_t dma_transfer(struct dw_spi *dws)
> @@ -178,6 +180,8 @@ static void dw_spi_dma_tx_done(void *arg)
>  	clear_bit(TX_BUSY, &dws->dma_chan_busy);
>  	if (test_bit(RX_BUSY, &dws->dma_chan_busy))
>  		return;
> +
> +	dw_writel(dws, DW_SPI_DMACR, 0);
>  	spi_finalize_current_transfer(dws->master);
>  }
>  
> @@ -249,6 +253,8 @@ static void dw_spi_dma_rx_done(void *arg)
>  	clear_bit(RX_BUSY, &dws->dma_chan_busy);
>  	if (test_bit(TX_BUSY, &dws->dma_chan_busy))
>  		return;
> +
> +	dw_writel(dws, DW_SPI_DMACR, 0);
>  	spi_finalize_current_transfer(dws->master);
>  }
>  
> @@ -342,6 +348,8 @@ static void mid_spi_dma_stop(struct dw_spi *dws)
>  		dmaengine_terminate_sync(dws->rxchan);
>  		clear_bit(RX_BUSY, &dws->dma_chan_busy);
>  	}
> +
> +	dw_writel(dws, DW_SPI_DMACR, 0);
>  }
>  
>  static const struct dw_spi_dma_ops mfld_dma_ops = {
> -- 
> 2.25.1
> 

-- 
With Best Regards,
Andy Shevchenko