Re: [PATCH 1/2] dmaengine: rcar-dmac: Don't set DMACHCLR bit 0 to 1 if iommu is mapped

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Shimoda-san,

On Wed, Aug 28, 2019 at 1:15 PM Yoshihiro Shimoda
<yoshihiro.shimoda.uh@renesas.com> wrote:
> The commit 20c169aceb45 ("dmaengine: rcar-dmac: clear pertinence
> number of channels") always set the DMACHCLR bit 0 to 1, but if
> iommu is mapped to the device, this driver doesn't need to clear it.
> So, this patch takes care of it by using "channels_mask" bitfield.
>
> Note that, this patch doesn't have a "Fixes:" tag because the driver
> doesn't manage the channel 0 anyway so that the behavior of
> the channel is not changed.
>
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> ---
>  drivers/dma/sh/rcar-dmac.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
> index 779b715..204160e 100644
> --- a/drivers/dma/sh/rcar-dmac.c
> +++ b/drivers/dma/sh/rcar-dmac.c
> @@ -192,6 +192,7 @@ struct rcar_dmac_chan {
>   * @iomem: remapped I/O memory base
>   * @n_channels: number of available channels
>   * @channels: array of DMAC channels
> + * @channels_mask: bitfield of which DMA channels are managed by this driver
>   * @modules: bitmask of client modules in use
>   */
>  struct rcar_dmac {
> @@ -202,6 +203,7 @@ struct rcar_dmac {
>
>         unsigned int n_channels;
>         struct rcar_dmac_chan *channels;
> +       unsigned int channels_mask;

Given you want to store the output of of_property_read_u32() here in a
subsequent patch, you may want to use u32 instead of unsigned int.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds