Re: [PATCH v4 7/7] clk: qcom: add the driver for the MSM8996 APCS clocks

[Dmitry Baryshkov]

On 25/01/2023 23:38, Stephen Boyd wrote:
> Quoting Dmitry Baryshkov (2023-01-18 05:22:54)
> > diff --git a/drivers/clk/qcom/apcs-msm8996.c b/drivers/clk/qcom/apcs-msm8996.c
> > new file mode 100644
> > index 000000000000..7e46ea8ed444
> > --- /dev/null
> > +++ b/drivers/clk/qcom/apcs-msm8996.c
> > @@ -0,0 +1,76 @@
> [...]
> > +
> > +static int qcom_apcs_msm8996_clk_probe(struct platform_device *pdev)
> > +{
> > +       struct device *dev = &pdev->dev;
> > +       struct device *parent = dev->parent;
> > +       struct regmap *regmap;
> > +       struct clk_hw *hw;
> > +       unsigned int val;
> > +       int ret = -ENODEV;
> > +
> > +       regmap = dev_get_regmap(parent, NULL);
> > +       if (!regmap) {
> > +               dev_err(dev, "failed to get regmap: %d\n", ret);
> > +               return ret;
> > +       }
> > +
> > +       regmap_read(regmap, APCS_AUX_OFFSET, &val);
> > +       regmap_update_bits(regmap, APCS_AUX_OFFSET, APCS_AUX_DIV_MASK,
> > +                          FIELD_PREP(APCS_AUX_DIV_MASK, APCS_AUX_DIV_2));
> > +
> > +       /* Hardware mandated delay */
>
> Delay for what? Setting the divider? What if the register value didn't
> change at all? Can you skip the delay in that case?

Ack, I'll expand the comment.

> > +       udelay(5);
> > +
> > +       /*
> > +        * Register the clock as fixed rate instead of being a child of gpll0
> > +        * to let the driver register probe as early as possible.
>
> The function doesn't block or return EPROBE_DEFER if the clk is orphaned
> when registered. Why is this necessary? Are you getting defered by the
> fw_devlink logic thinking it needs to defer probe of this driver until
> gpll0 provider probes? We should fix fw_devlink to not do that. Maybe if
> the node is a clk provider (#clock-cells exists) then we don't wait for
> clocks property to be provided, because the clk core already handles
> that itself.

Letting clock-controllers probe was my idea for the patch, but it was 
delayed again by Saravana, see [1], [2]

[1] 
https://lore.kernel.org/all/20230118091122.2205452-1-dmitry.baryshkov@xxxxxxxxxx/

[2] 
https://lore.kernel.org/all/CAGETcx8Xy5OzsbW3123esxsbQJq-SqDkP1S5g2mmwzoCz4shtQ@xxxxxxxxxxxxxx/

> > +        */
> > +       hw = devm_clk_hw_register_fixed_rate(dev, "sys_apcs_aux", NULL, 0, 300000000);

--
With best wishes
Dmitry