[PATCH v10 3/4] pwm: add microchip soft ip corePWM driver

Uwe Kleine-König u.kleine-koenig at pengutronix.de
Fri Sep 30 02:13:16 PDT 2022


On Mon, Sep 19, 2022 at 03:29:19PM +0100, Conor Dooley wrote:
> Hey Uwe,
> 
> On Mon, Sep 19, 2022 at 03:50:08PM +0200, Uwe Kleine-König wrote:
> > On Mon, Sep 19, 2022 at 01:53:56PM +0100, Conor Dooley wrote:
> > > Because I was running into conflicts between the reporting here and some
> > > of the checks that I have added to prevent the PWM being put into an
> > > invalid state. On boot both negedge and posedge will be zero & this was
> > > preventing me from setting the period at all.
> > 
> > I don't understood that.
> 
> On startup, (negedge == posedge) is true as both are zero, but the reset
> values for prescale and period are actually 0x8. If on reset I try to
> set a small period, say "echo 1000 > period" apply() returns -EINVAL
> because of a check in the pwm core in pwm_apply_state() as I am
> attempting to set the period to lower than the out-of-reset duty cycle.

You're supposed to keep the period for pwm#1 untouched while configuring
pwm#0 only if pwm#1 already has a consumer. So if pwm#1 isn't requested,
you can change the period for pwm#0.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 488 bytes
Desc: not available
URL: <http://lists.infradead.org/pipermail/linux-riscv/attachments/20220930/bbad3d6d/attachment.sig>


More information about the linux-riscv mailing list