Re: [PATCH v14 20/39] pwm: tegra: Add runtime PM and OPP support

On Fri, 29 Oct 2021 at 17:20, Dmitry Osipenko digetx@gmail.com wrote:

26.10.2021 01:40, Dmitry Osipenko пишет:

...

• ret = devm_pm_runtime_enable(&pdev->dev);
  

• if (ret)
  

•         return ret;
  

• ret = devm_tegra_core_dev_init_opp_table_common(&pdev->dev);
  

• if (ret)
  

•         return ret;
  

• ret = pm_runtime_resume_and_get(&pdev->dev);
  

• if (ret)
  

•         return ret;
  

• /* Set maximum frequency of the IP */
  

• ret = clk_set_rate(pwm->clk, pwm->soc->max_frequency);
  

• ret = dev_pm_opp_set_rate(pwm->dev, pwm->soc->max_frequency);
  if (ret < 0) {
          dev_err(&pdev->dev, "Failed to set max frequency: %d\n", ret);
  

•         return ret;
  

•         goto put_pm;
  }
  
  /*
  

@@ -278,7 +294,7 @@ static int tegra_pwm_probe(struct platform_device *pdev) if (IS_ERR(pwm->rst)) { ret = PTR_ERR(pwm->rst); dev_err(&pdev->dev, "Reset control is not found: %d\n", ret);

•         return ret;
  

•         goto put_pm;
  }
  
  reset_control_deassert(pwm->rst);
  

@@ -291,10 +307,15 @@ static int tegra_pwm_probe(struct platform_device *pdev) if (ret < 0) { dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret); reset_control_assert(pwm->rst);

•         return ret;
  

•         goto put_pm;
  }
  
  

• pm_runtime_put(&pdev->dev);
  

• return 0;
  

+put_pm:

• pm_runtime_put_sync_suspend(&pdev->dev);
  

• return ret;
  

}

static int tegra_pwm_remove(struct platform_device *pdev) @@ -305,20 +326,44 @@ static int tegra_pwm_remove(struct platform_device *pdev)

  reset_control_assert(pc->rst);

• pm_runtime_force_suspend(&pdev->dev);
  

I just noticed that RPM core doesn't reset RPM-enable count of a device on driver's unbind (pm_runtime_reinit). It was a bad idea to use devm_pm_runtime_enable() + pm_runtime_force_suspend() here, since RPM is disabled twice on driver's removal, and thus, RPM will never be enabled again.

I'll fix it for PWM and other drivers in this series, in v15.

Good catch - and sorry for not spotting it while reviewing!

Maybe devm_pm_runtime_enable() isn't that useful after all? Should we suggest to remove it so others don't fall into the same trap?

Kind regards Uffe