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

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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




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