linux-kernel - Re: [PATCH] staging: greybus: introduce pwm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <6acc4f74-31a1-75b2-f7e8-610aac7b0ec8@189.cn>
Date:   Fri, 11 Feb 2022 11:06:33 +0800
From:   Song Chen <chensong_2000@....cn>
To:     Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc:     johan@...nel.org, elder@...nel.org, gregkh@...uxfoundation.org,
        thierry.reding@...il.com, lee.jones@...aro.org,
        greybus-dev@...ts.linaro.org, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org
Subject: Re: [PATCH] staging: greybus: introduce pwm_ops::apply



在 2022/2/10 18:03, Uwe Kleine-König 写道:
> On Thu, Feb 10, 2022 at 05:05:02PM +0800, Song Chen wrote:
>> Introduce apply in pwm_ops to replace legacy operations,
>> like enable, disable, config and set_polarity.
>>
>> Signed-off-by: Song Chen <chensong_2000@....cn>
>> ---
>>   drivers/staging/greybus/pwm.c | 46 +++++++++++++++--------------------
>>   1 file changed, 19 insertions(+), 27 deletions(-)
>>
>> diff --git a/drivers/staging/greybus/pwm.c b/drivers/staging/greybus/pwm.c
>> index 891a6a672378..e1889cf979b2 100644
>> --- a/drivers/staging/greybus/pwm.c
>> +++ b/drivers/staging/greybus/pwm.c
>> @@ -204,43 +204,35 @@ static void gb_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
>>   	gb_pwm_deactivate_operation(pwmc, pwm->hwpwm);
>>   }
>>   
>> -static int gb_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
>> -			 int duty_ns, int period_ns)
>> -{
>> -	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
>> -
>> -	return gb_pwm_config_operation(pwmc, pwm->hwpwm, duty_ns, period_ns);
>> -};
>> -
>> -static int gb_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
>> -			       enum pwm_polarity polarity)
>> +static int gb_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>> +			const struct pwm_state *state)
>>   {
>> +	int ret;
>>   	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
>>   
>> -	return gb_pwm_set_polarity_operation(pwmc, pwm->hwpwm, polarity);
>> -};
>> -
>> -static int gb_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
>> -{
>> -	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);
>> +	/* set period and duty cycle*/
>> +	ret = gb_pwm_config_operation(pwmc, pwm->hwpwm, state->duty_cycle, state->period);
> 
> gb_pwm_config_operation's 3rd parameter is an u32, so you're loosing
> bits here as state->duty_cycle is a u64. Ditto for period.

originally, pwm_apply_state --> pwm_apply_legacy --> gb_pwm_config --> 
gb_pwm_config_operation is also loosing bits, does it mean greybus can 
live with that?

Or redefine gb_pwm_config_request, switch duty and period to __le64?

> 
> Also it would be nice if you go from
> 
> 	.duty_cycle = A, .period = B, .enabled = 1
> 
> to
> 
> 	.duty_cycle = C, .period = D, .enabled = 0
> 
> that C/D wasn't visible on the output pin. So please disable earlier
> (but keep enable at the end).

sorry, i don't quite understand this part, but is below code looking 
good to you?

static int gb_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
			const struct pwm_state *state)
{
	int err;
	bool enabled = pwm->state.enabled;
	struct gb_pwm_chip *pwmc = pwm_chip_to_gb_pwm_chip(chip);

	/* set polarity */
	if (state->polarity != pwm->state.polarity) {
		if (enabled) {
			gb_pwm_disable_operation(pwmc, pwm->hwpwm);
			enabled = false;
		}
		err = gb_pwm_set_polarity_operation(pwmc, pwm->hwpwm, state->polarity);
		if (err)
			return err;
	}

	if (!state->enabled) {
		if (enabled)
			gb_pwm_disable_operation(pwmc, pwm->hwpwm);
		return 0;
	}

	/* set period and duty cycle*/
	err = gb_pwm_config_operation(pwmc, pwm->hwpwm, state->duty_cycle, 
state->period);
	if (err)
		return err;

	/* enable/disable */
	if (!enabled)
		return gb_pwm_enable_operation(pwmc, pwm->hwpwm);

	return 0;
}

> 
> Best regards
> Uwe
>