On Fri, Dec 07, 2018 at 05:29:33PM +0900, Yoshihiro Shimoda wrote:
> This PWM Timer cannot output low because setting 0x000 is prohibited
> on PWMCNT.PH0 (High-Level Period) bitfields. So, avoiding
> the prohibited, this patch adds a workaround function to change
> the value from 0 to 1 as pseudo low level.
>
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
> ---
> drivers/pwm/pwm-rcar.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/drivers/pwm/pwm-rcar.c b/drivers/pwm/pwm-rcar.c
> index e479b6a..888cb37 100644
> --- a/drivers/pwm/pwm-rcar.c
> +++ b/drivers/pwm/pwm-rcar.c
> @@ -166,6 +166,20 @@ static void rcar_pwm_disable(struct rcar_pwm_chip *rp)
> rcar_pwm_update(rp, RCAR_PWMCR_EN0, 0, RCAR_PWMCR);
> }
>
> +static void rcar_pwm_workaround_output_low(struct rcar_pwm_chip *rp)
> +{
> + /*
> + * This PWM Timer cannot output low because setting 0x000 is
> + * prohibited on PWMCNT.PH0 (High-Level Period) bitfields. So, avoiding
> + * the prohibited, this function changes the value from 0 to 1 as
> + * pseudo low level.
> + *
> + * TODO: Add GPIO handling to output low level.
> + */
> + if ((rp->pwmcnt & RCAR_PWMCNT_PH0_MASK) == 0)
> + rp->pwmcnt |= 1;
In my eyes this is too broken to do. Not sure I have the complete
picture, but given a small period (say 2) this 1 cycle might result in
50 % duty cycle. Depending on how the hardware behaves if you disable
it, better do this instead.
Are you aware of the series adding such gpio support to the imx driver?
@Thierry: So there are three drivers now that could benefit for a
generic approach.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
