[PATCH] pwm: lpc32xx: Set PWM_PIN_LEVEL bit in lpc32xx_pwm_disable
thierry.reding at gmail.com
Wed Jun 22 07:36:50 PDT 2016
On Wed, Jun 22, 2016 at 09:26:04AM -0400, Sylvain Lemieux wrote:
> Hi Thierry,
> On Wed, 2016-06-22 at 14:32 +0200, Thierry Reding wrote:
> > On Fri, Jun 03, 2016 at 03:37:57PM -0400, Sylvain Lemieux wrote:
> > > From: Sylvain Lemieux <slemieux at tycoint.com>
> > >
> > > If the PWM_PIN_LEVEL bit is setup to 1 in the bootloader, when the kernel
> > > disable the PWM, the PWM output is always set as a logic 1.
> > I presume there's a reason why the bootloader set this bit to 1. Why do
> > you assume it's the right thing to clear it?
> There is an alternative mode for the PWM output pin; using the
> PWM_PIN_LEVEL bit to control the PWM output (logical 0 or 1 on
> output) when the PWM is disable.
> In this case, the bootloader is using the PWM_PIN_LEVEL bit
> to control the PWM output (always 1) to enable the LCD; the
> application is using the PWM to control the intensity of the
> LCD output. When disabling the PWM, the line level should be
> setup to 0.
But doesn't that mean that if the pin is used in PWM mode there's never
a use-case for having it go high when disabled? Given that this is a PWM
driver I don't see how we'd ever be in the case where the alternate
setting makes sense.
> A version 2 of this patch will be send with support to select
> the alternate PWM disable level high from the device tree.
> For details, you can refer to:
Given the above I don't think we should add this new device tree
property until we encounter a setup where it's needed.
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