Re: [PATCH v2 2/3] dma: imx-sdma: add clock ratio 1:1 check

[Daniel Baluta <daniel.baluta@gmail.com>]

On Sun, Jan 20, 2019 at 4:32 AM Angus Ainslie (Purism) <angus@akkea.ca> wrote:
>
> On i.mx8 mscale B0 chip, AHB/SDMA clock ratio 2:1 can't be supportted,
> since SDMA clock ratio has to be increased to 250Mhz, AHB can't reach
> to 500Mhz, so use 1:1 instead.
>
> based on NXP commit MLK-16841-1

Hi Angus,

Thanks for doing this!

I'm not sure specifying the MLK here helps. I think it would be better
to somehow add the original Signed-off-by and mention that the commit
was pulled from NXP linux-imx tree.
>
> Signed-off-by: Angus Ainslie (Purism) <angus@akkea.ca>
> ---
>  .../devicetree/bindings/dma/fsl-imx-sdma.txt  |  1 +
>  drivers/dma/imx-sdma.c                        | 20 +++++++++++++++----
>  2 files changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt b/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt
> index 3c9a57a8443b..17544c1820b7 100644
> --- a/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt
> +++ b/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt
> @@ -67,6 +67,7 @@ Optional properties:
>      reg is the GPR register offset.
>      shift is the bit position inside the GPR register.
>      val is the value of the bit (0 or 1).
> +- fsl,ratio-1-1: AHB/SDMA core clock ration 1:1, 2:1 without this.
>
>  Examples:
>
> diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> index 0b3a67ff8e82..65dada21d3c1 100644
> --- a/drivers/dma/imx-sdma.c
> +++ b/drivers/dma/imx-sdma.c
> @@ -440,6 +440,8 @@ struct sdma_engine {
>         unsigned int                    irq;
>         dma_addr_t                      bd0_phys;
>         struct sdma_buffer_descriptor   *bd0;
> +       /* clock ratio for AHB:SDMA core. 1:1 is 1, 2:1 is 0*/
> +       bool                            clk_ratio;
>  };
>
>  static int sdma_config_write(struct dma_chan *chan,
> @@ -662,8 +664,14 @@ static int sdma_run_channel0(struct sdma_engine *sdma)
>                 dev_err(sdma->dev, "Timeout waiting for CH0 ready\n");
>
>         /* Set bits of CONFIG register with dynamic context switching */
> -       if (readl(sdma->regs + SDMA_H_CONFIG) == 0)
> -               writel_relaxed(SDMA_H_CONFIG_CSM, sdma->regs + SDMA_H_CONFIG);
> +       if (readl(sdma->regs + SDMA_H_CONFIG) == 0) {
> +               if (sdma->clk_ratio)
> +                       reg = SDMA_H_CONFIG_CSM | SDMA_H_CONFIG_ACR;
> +               else
> +                       reg = SDMA_H_CONFIG_CSM;
> +
> +               writel_relaxed(reg, sdma->regs + SDMA_H_CONFIG);
> +       }
>
>         return ret;
>  }
> @@ -1880,8 +1888,10 @@ static int sdma_init(struct sdma_engine *sdma)
>         writel_relaxed(0x4050, sdma->regs + SDMA_CHN0ADDR);
>
>         /* Set bits of CONFIG register but with static context switching */
> -       /* FIXME: Check whether to set ACR bit depending on clock ratios */
> -       writel_relaxed(0, sdma->regs + SDMA_H_CONFIG);
> +       if (sdma->clk_ratio)
> +               writel_relaxed(SDMA_H_CONFIG_ACR, sdma->regs + SDMA_H_CONFIG);
> +       else
> +               writel_relaxed(0, sdma->regs + SDMA_H_CONFIG);
>
>         writel_relaxed(ccb_phys, sdma->regs + SDMA_H_C0PTR);
>
> @@ -1975,6 +1985,8 @@ static int sdma_probe(struct platform_device *pdev)
>         if (!sdma)
>                 return -ENOMEM;
>
> +       sdma->clk_ratio = of_property_read_bool(np, "fsl,ratio-1-1");
> +
>         spin_lock_init(&sdma->channel_0_lock);
>
>         sdma->dev = &pdev->dev;
> --
> 2.17.1
>