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

[Jagan Teki]

Hi Maxime,

On Sun, Nov 3, 2019 at 11:02 PM Maxime Ripard <mripard@xxxxxxxxxx> 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@xxxxxxxxxx> 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);
+    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);
+    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);
+    }
+
+    regmap_exit(dsi->regs);
+
     return 0;
 }


Jagan.