Re: [PATCH v6 2/2] pwm: Add support for RZ/G2L GPT

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

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Hello,

On Wed, Sep 21, 2022 at 01:46:54PM +0000, Biju Das wrote:
> > Actually it's worse:
> > 
> > - When both channels are used, setting the duty-cycle on one aborts the
> >   currently running period on the other and starts it anew.
> > 
> > (Did I get this correctly?)
> 
> I think, I have fixed that issue with the below logic
> Which allows to update duty cycle on the fly.
> 
> Now the only limitation is w.r.to disabling channels
> as we need to disable together as stopping the counter
> affects both.
> 
>       /*
> 	 * Counter must be stopped before modifying mode, prescaler, timer
> 	 * counter and buffer enable registers. These registers are shared
> 	 * between both channels. So allow updating these registers only for the
> 	 * first enabled channel.
> 	 */
> 	if (rzg2l_gpt->user_count <= 1)
> 		rzg2l_gpt_disable(rzg2l_gpt);
> 
> 	is_counter_running = rzg2l_gpt_read(rzg2l_gpt, RZG2L_GTCR) & RZG2L_GTCR_CST;
> 	if (!is_counter_running)
> 		/* GPT set operating mode (saw-wave up-counting) */
> 		rzg2l_gpt_modify(rzg2l_gpt, RZG2L_GTCR, RZG2L_GTCR_MD,
> 				 RZG2L_GTCR_MD_SAW_WAVE_PWM_MODE);

So if the PWM is already running (e.g. from the bootloader) and the mode
is wrong, this isn't fixed? Similar problems in the if blocks below.

> 	/* Set count direction */
> 	rzg2l_gpt_write(rzg2l_gpt, RZG2L_GTUDDTYC, RZG2L_UP_COUNTING);
> 
> 	if (!is_counter_running)
> 		/* Select count clock */
> 		rzg2l_gpt_modify(rzg2l_gpt, RZG2L_GTCR, RZG2L_GTCR_TPCS,
> 				 FIELD_PREP(RZG2L_GTCR_TPCS, prescale));
> 
> 	/* Set period */
> 	rzg2l_gpt_write(rzg2l_gpt, RZG2L_GTPR, pv);
> 
> 	/* Set duty cycle */
> 	rzg2l_gpt_write(rzg2l_gpt, RZG2L_GTCCR(pwm->hwpwm), dc);
> 
> 	if (!is_counter_running) {
> 		/* Set initial value for counter */
> 		rzg2l_gpt_write(rzg2l_gpt, RZG2L_GTCNT, 0);
> 
> 		/* Set no buffer operation */
> 		rzg2l_gpt_write(rzg2l_gpt, RZG2L_GTBER, 0);
> 	}

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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