Hi Janusz,
Am Montag, den 08.12.2014, 21:03 +0100 schrieb Janusz Użycki:
> Hi,
>
> I've fixed my pwm driver and I can enable 12MHz 50% output using sysfs.
> Then I rebased the pwm-clock to 3.14.
> I have connected mcp2515 and it works with fixed clock. When I switch
> the chip's clock to pwm clock in dt
> I get "mcp251x: probe of spi1.2 failed with error -2". I've also added
> clock-frequency property
> but it didn't help.
> When I set the mcp2515 clock to fixed clock again but the clock is not
> applied to mcp2515 I get
> "mcp251x spi1.2: MCP251x didn't enter in conf mode after reset".
> So it looks this is indeed probe error caused likely by dt.
Did pwm-clock fail to probe already? Could you check with the patch
below?
> The fixed and pwm clock in DT:
> clocks {
> #address-cells = <1>;
> #size-cells = <1>;
> ranges;
> mcp251x_xtal_clk: mcp2515_xtal {
> compatible = "fixed-clock";
> #clock-cells = <0>;
> clock-frequency = <12000000>;
> };
>
> mcp251x_pwm_clk: mcp2515_pwm {
> compatible = "pwm-clock";
> #clock-cells = <0>;
> clock-frequency = <12000000>;
> clock-output-names = "can_clk";
> pwms = <&pwm 3 83>; /* 12MHz = 1 / ~83ns */
> };
> };
>
> Also the mentioned frequency recalculation problem appears here.
> In the case above recalc value is about 12.048MHz instead of 12.0MHz.
> While PWM block is clocked 24MHz and the pwm generates exactly 12MHz
> the pwm-clock driver returns drifted value. Using clock-frequency like
> fixed-clock does could simply solve the binding problem.
Yes, for this case it is very unfortunate that there's only nanosecond
resolution for the duty cycle. Adding a clock-frequency property to
indicate the real frequency would solve this problem.
------8<------
diff --git a/drivers/clk/clk-pwm.c b/drivers/clk/clk-pwm.c
index 8f747b3..9c13856 100644
--- a/drivers/clk/clk-pwm.c
+++ b/drivers/clk/clk-pwm.c
@@ -63,12 +63,16 @@ int clk_pwm_probe(struct platform_device *pdev)
return -ENOMEM;
pwm = devm_pwm_get(&pdev->dev, NULL);
- if (IS_ERR(pwm))
+ if (IS_ERR(pwm)) {
+ dev_err(&pdev->dev, "failed to get pwm: %ld\n", PTR_ERR(pwm));
return PTR_ERR(pwm);
+ }
ret = pwm_config(pwm, (pwm->period + 1) >> 1, pwm->period);
- if (ret < 0)
+ if (ret < 0) {
+ dev_err(&pdev->dev, "failed to configure pwm: %d\n", ret);
return ret;
+ }
init.name = "pwm-clock";
init.ops = &clk_pwm_ops;
@@ -78,11 +82,18 @@ int clk_pwm_probe(struct platform_device *pdev)
clk_pwm->pwm = pwm;
clk_pwm->hw.init = &init;
clk = devm_clk_register(&pdev->dev, &clk_pwm->hw);
- if (IS_ERR(clk))
+ if (IS_ERR(clk)) {
+ dev_err(&pdev->dev, "failed to register clock: %ld\n",
+ PTR_ERR(clk));
return PTR_ERR(clk);
+ }
- return of_clk_add_provider(pdev->dev.of_node,
- of_clk_src_simple_get, clk);
+ ret = of_clk_add_provider(pdev->dev.of_node,
+ of_clk_src_simple_get, clk);
+ if (ret)
+ dev_err(&pdev->dev, "failed to add clock provider: %d\n", ret);
+
+ return ret;
}
int clk_pwm_remove(struct platform_device *pdev)
--
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