Re: [PATCH] hwmon: (aspeed-pwm-tacho) Deassert reset in probe

[Guenter Roeck]

On 10/31/2017 07:04 PM, Stafford Horne wrote:
> On Tue, Oct 31, 2017 at 06:53:15PM -0700, Guenter Roeck wrote:
> > On 10/31/2017 06:34 PM, Joel Stanley wrote:
> > > The ASPEED SoC must deassert a reset in order to use the PWM/tach
> > > peripheral.
> > >
> > > The device tree bindings are updated to document the resets phandle, and
> > > the example is updated to match what is expected for both the reset and
> > > clock phandle. Note that the bindings should have always had the reset
> > > controller, as the hardware is unusable without it.
> > >
> > > Signed-off-by: Joel Stanley <joel@xxxxxxxxx>
> >
> > Presumably the driver is being used. This change makes it incompatible with
> > existing users. This is unacceptable; after all, it is possible that the
> > device is taken out of reset by ROMMON or BIOS.
> >
> > On top of that, the reset controller code is quite strict and issues a
> > backtrace if CONFIG_RESET_CONTROLLER is not enabled. Yet, there is no
> > dependency added on RESET_CONTROLLER. You might want to consider making
> > the new control optional and using devm_reset_control_get_optional_exclusive().
> >
> > The DT change should be a separate patch.
> >
> > More comments below.
>
> [..]
>
> > >    	return PTR_ERR_OR_ZERO(hwmon);
> > >    }
> > > +static int aspeed_pwm_tacho_remove(struct platform_device *pdev)
> > > +{
> > > +	struct aspeed_pwm_tacho_data *priv = platform_get_drvdata(pdev);
> > > +
> > > +	reset_control_deassert(priv->rst);
> >
> > This seems to be quite pointless. Also, did you test this code ?
> >
> > > +
> > > +	return 0;
> > > +}
> > > +
> > >    static const struct of_device_id of_pwm_tacho_match_table[] = {
> > >    	{ .compatible = "aspeed,ast2400-pwm-tacho", },
> > >    	{ .compatible = "aspeed,ast2500-pwm-tacho", },
> > > @@ -969,6 +989,7 @@ MODULE_DEVICE_TABLE(of, of_pwm_tacho_match_table);
> > >    static struct platform_driver aspeed_pwm_tacho_driver = {
> > >    	.probe		= aspeed_pwm_tacho_probe,
> > > +	.probe		= aspeed_pwm_tacho_remove,
>
> Also, this cant be right (should be .remove)?

Nice. Makes me really wonder what this code would do. Does this even compile ?

Guenter