Re: [PATCH] spi: spi-rspi: Add force_dma variable to spi_ops

[Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>]

Hi Biju,

On Sat, Jul 16, 2022 at 5:39 PM Biju Das <biju.das.jz@xxxxxxxxxxxxxx> wrote:
> On RZ/G2L SoCs switching from DMA to interrupt mode, causes timeout
> issue as we are not getting Rx interrupt even though SPRF bit is set in
> the status register.
>
> But there is no issue if we don't switch between interrupt to DMA mode
> or vice versa.
>
> Performance comparison between interrupt and DMA mode on RZ/Five SMARC
> platform connected to a display module shows that performance and
> CPU utilization is much better with DMA mode compared to interrupt mode
> (1->65 fps) and (98->8%).
>
> This patch introduces a variable force_dma to avoid switching between
> DMA to interrupt mode for RZ platforms.
>
> Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>

Thanks for your patch!

> @@ -1196,6 +1197,7 @@ static const struct spi_ops rspi_rz_ops = {
>         .flags =                SPI_CONTROLLER_MUST_RX | SPI_CONTROLLER_MUST_TX,
>         .fifo_size =            8,      /* 8 for TX, 32 for RX */
>         .num_hw_ss =            1,
> +       .force_dma =            true,
>  };

Do you know if this is needed on RZ/A series, too?
I know upstream does not have DMA support for RZ/A yet, but the
BSP has?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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when I'm talking to journalists I just say "programmer" or something like that.
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