Re: [PATCH v11 4/7] drm/sun4i: dsi: Handle bus clock explicitly

[Maxime Ripard <maxime@cerno.tech>]

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Hi,

On Thu, Nov 21, 2019 at 05:24:47PM +0530, Jagan Teki wrote:
> On Sun, Nov 3, 2019 at 11:02 PM Maxime Ripard <mripard@kernel.org> wrote:
> >
> > On Fri, Nov 01, 2019 at 07:42:55PM +0530, Jagan Teki wrote:
> > > Hi Maxime,
> > >
> > > On Tue, Oct 29, 2019 at 2:24 PM Maxime Ripard <mripard@kernel.org> wrote:
> > > >
> > > > On Tue, Oct 29, 2019 at 04:03:56AM +0530, Jagan Teki wrote:
> > > > > > > explicit handling of common clock would require since the A64
> > > > > > > doesn't need to mention the clock-names explicitly in dts since it
> > > > > > > support only one bus clock.
> > > > > > >
> > > > > > > Also pass clk_id NULL instead "bus" to regmap clock init function
> > > > > > > since the single clock variants no need to mention clock-names
> > > > > > > explicitly.
> > > > > >
> > > > > > You don't need explicit clock handling. Passing NULL as the argument
> > > > > > in regmap_init_mmio_clk will make it use the first clock, which is the
> > > > > > bus clock.
> > > > >
> > > > > Indeed I tried that, since NULL clk_id wouldn't enable the bus clock
> > > > > during regmap_mmio_gen_context code, passing NULL triggering vblank
> > > > > timeout.
> > > >
> > > > There's a bunch of users of NULL in tree, so finding out why NULL
> > > > doesn't work is the way forward.
> > >
> > > I'd have looked the some of the users before checking the code as
> > > well. As I said passing NULL clk_id to devm_regmap_init_mmio_clk =>
> > > __devm_regmap_init_mmio_clk would return before processing the clock.
> > >
> > > Here is the code snippet on the tree just to make sure I'm on the same
> > > page or not.
> > >
> > > static struct regmap_mmio_context *regmap_mmio_gen_context(struct device *dev,
> > >                                         const char *clk_id,
> > >                                         void __iomem *regs,
> > >                                         const struct regmap_config *config)
> > > {
> > >         -----------------------
> > >         --------------
> > >         if (clk_id == NULL)
> > >                 return ctx;
> > >
> > >         ctx->clk = clk_get(dev, clk_id);
> > >         if (IS_ERR(ctx->clk)) {
> > >                 ret = PTR_ERR(ctx->clk);
> > >                 goto err_free;
> > >         }
> > >
> > >         ret = clk_prepare(ctx->clk);
> > >         if (ret < 0) {
> > >                 clk_put(ctx->clk);
> > >                 goto err_free;
> > >         }
> > >         -------------
> > >         ---------------
> > > }
> > >
> > > Yes, I did check on the driver in the tree before committing explicit
> > > clock handle, which make similar requirements like us in [1]. this
> > > imx2 wdt driver is handling the explicit clock as well. I'm sure this
> > > driver is updated as I have seen few changes related to this driver in
> > > ML.
> >
> > I guess we have two ways to go at this then.
> >
> > Either we remove the return, but it might have a few side-effects, or
> > we call clk_get with NULL or bus depending on the case, and then call
> > regmap_mmio_attach_clk.
>
> Thanks for the inputs.
>
> Please have a look at this snippet, I have used your second
> suggestions. let me know if you have any comments?
>
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> index 8fa90cfc2ac8..91c95e56d870 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> @@ -1109,24 +1109,36 @@ static int sun6i_dsi_probe(struct platform_device *pdev)
>          return PTR_ERR(dsi->regulator);
>      }
>
> -    dsi->regs = devm_regmap_init_mmio_clk(dev, "bus", base,
> -                          &sun6i_dsi_regmap_config);
> -    if (IS_ERR(dsi->regs)) {
> -        dev_err(dev, "Couldn't create the DSI encoder regmap\n");
> -        return PTR_ERR(dsi->regs);
> -    }
> -
>      dsi->reset = devm_reset_control_get_shared(dev, NULL);
>      if (IS_ERR(dsi->reset)) {
>          dev_err(dev, "Couldn't get our reset line\n");
>          return PTR_ERR(dsi->reset);
>      }
>
> +    dsi->regs = regmap_init_mmio(dev, base, &sun6i_dsi_regmap_config);

You should use the devm variant here

> +    if (IS_ERR(dsi->regs)) {
> +        dev_err(dev, "Couldn't init regmap\n");
> +        return PTR_ERR(dsi->regs);
> +    }
> +
> +    dsi->bus_clk = devm_clk_get(dev, NULL);

I guess you still need to pass 'bus' here?

> +    if (IS_ERR(dsi->bus_clk)) {
> +        dev_err(dev, "Couldn't get the DSI bus clock\n");
> +        ret = PTR_ERR(dsi->bus_clk);
> +        goto err_regmap;
> +    } else {
> +        printk("Jagan.. Got the BUS clock\n");
> +        ret = regmap_mmio_attach_clk(dsi->regs, dsi->bus_clk);
> +        if (ret)
> +            goto err_bus_clk;
> +    }
> +
>      if (dsi->variant->has_mod_clk) {
>          dsi->mod_clk = devm_clk_get(dev, "mod");
>          if (IS_ERR(dsi->mod_clk)) {
>              dev_err(dev, "Couldn't get the DSI mod clock\n");
> -            return PTR_ERR(dsi->mod_clk);
> +            ret = PTR_ERR(dsi->mod_clk);
> +            goto err_attach_clk;
>          }
>      }
>
> @@ -1167,6 +1179,14 @@ static int sun6i_dsi_probe(struct platform_device *pdev)
>  err_unprotect_clk:
>      if (dsi->variant->has_mod_clk)
>          clk_rate_exclusive_put(dsi->mod_clk);
> +err_attach_clk:
> +    if (!IS_ERR(dsi->bus_clk))
> +        regmap_mmio_detach_clk(dsi->regs);
> +err_bus_clk:
> +    if (!IS_ERR(dsi->bus_clk))
> +        clk_put(dsi->bus_clk);
> +err_regmap:
> +    regmap_exit(dsi->regs);
>      return ret;
>  }
>
> @@ -1181,6 +1201,13 @@ static int sun6i_dsi_remove(struct platform_device *pdev)
>      if (dsi->variant->has_mod_clk)
>          clk_rate_exclusive_put(dsi->mod_clk);
>
> +    if (!IS_ERR(dsi->bus_clk)) {
> +        regmap_mmio_detach_clk(dsi->regs);
> +        clk_put(dsi->bus_clk);

This will trigger a warning, you put down the reference twice

Maxime

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