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

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Message-ID: <CAMty3ZBBkAk3==9u9XS3utms8GZD-5wPKu1WSR3byh5h-tY8aw@mail.gmail.com>
Date:   Tue, 3 Dec 2019 12:08:06 +0530
From:   Jagan Teki <jagan@...rulasolutions.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Mark Rutland <mark.rutland@....com>,
        devicetree <devicetree@...r.kernel.org>,
        David Airlie <airlied@...ux.ie>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Michael Trimarchi <michael@...rulasolutions.com>,
        linux-amarula <linux-amarula@...rulasolutions.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Icenowy Zheng <icenowy@...c.io>
Subject: Re: [PATCH v11 4/7] drm/sun4i: dsi: Handle bus clock explicitly

On Thu, Nov 28, 2019 at 11:21 PM Maxime Ripard <maxime@...no.tech> wrote:
>
> On Sat, Nov 23, 2019 at 01:20:21AM +0530, Jagan Teki wrote:
> > > > 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
> >
> > Sure.
> >
> > >
> > > > +    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?
> >
> > But the idea here is not to specify clock name explicitly to support
> > A64. otherwise A64 would fail as we are not specifying the clock-names
> > explicitly on dsi node.
>
> Right. But you have no guarantee that the bus clock is going to be the
> first one on the other SoCs either.
>
> What about something like that instead:
>
> char *clk_name = NULL;
> if (dsi->has_mod_clk)
>     clk_name = "bus";
>
> clk = devm_clk_get(dev, clk_name);
> if (IS_ERR(clk))
>     return PTR_ERR(clk));
>
> regmap_mmio_attach_clk(regmap, clk);

This makes sense, thanks for your input. I have tested in A33, A64.

>
> >
> > dsi: dsi@...0000 {
> >        compatible = "allwinner,sun50i-a64-mipi-dsi";
> >        reg = <0x01ca0000 0x1000>;
> >        interrupts = <GIC_SPI 89 IRQ_TYPE_LEVEL_HIGH>;
> >        clocks = <&ccu CLK_BUS_MIPI_DSI>;
> >        resets = <&ccu RST_BUS_MIPI_DSI>;
> >       phys = <&dphy>;
> >       phy-names = "dphy";
> > .....
> > };
> >
> > >
> > > > +    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
> >
> > You mean regmap_mmio_detach_clk will put the clk?
>
> No, devm_clk_get will.

Got it. Will update and send v12.

Jagan.