From: Hans de Goede <hdegoede@redhat.com>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: "Thierry Reding" <thierry.reding@gmail.com>,
"Jani Nikula" <jani.nikula@linux.intel.com>,
"Joonas Lahtinen" <joonas.lahtinen@linux.intel.com>,
"Ville Syrjälä" <ville.syrjala@linux.intel.com>,
"Rafael J . Wysocki" <rjw@rjwysocki.net>,
"Len Brown" <lenb@kernel.org>,
linux-pwm@vger.kernel.org,
intel-gfx <intel-gfx@lists.freedesktop.org>,
dri-devel@lists.freedesktop.org,
"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
"Mika Westerberg" <mika.westerberg@linux.intel.com>,
linux-acpi@vger.kernel.org
Subject: Re: [PATCH v3 04/15] pwm: lpss: Add range limit check for the base_unit register value
Date: Tue, 7 Jul 2020 19:31:29 +0200 [thread overview]
Message-ID: <1496178b-ce39-9285-ff75-cd39bc0e9aa7@redhat.com> (raw)
In-Reply-To: <20200707073424.w6vd6e4bhl56kosd@pengutronix.de>
Hi,
On 7/7/20 9:34 AM, Uwe Kleine-König wrote:
> On Mon, Jul 06, 2020 at 10:53:08PM +0200, Hans de Goede wrote:
>> Hi,
>>
>> Thank you for your review and sorry for the slow reply.
>
> No problem for me, I didn't hold my breath :-)
>
>>>> diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
>>>> index 43b1fc634af1..80d0f9c64f9d 100644
>>>> --- a/drivers/pwm/pwm-lpss.c
>>>> +++ b/drivers/pwm/pwm-lpss.c
>>>> @@ -97,6 +97,9 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm,
>>>> freq *= base_unit_range;
>>>> base_unit = DIV_ROUND_CLOSEST_ULL(freq, c);
>>>
>>> DIV_ROUND_CLOSEST_ULL is most probably wrong, too. But I didn't spend
>>> the time to actually confirm that.
>>
>> Yes I saw your comment elsewhere that the PWM API defines rounding
>> in a certain direction, but fixing that falls outside of this patch.
>
> Yeah, sure.
>
>> [...]
>> I hope this helps to explain what is going on a bit.
>
> I will try to make sense of that and reply to the patch directly when I
> succeeded.
>
>> ###
>>
>> As for the behavior on base_unit==0 in the get_state method,
>> as mentioned above I wrote that when I did not fully understood
>> how the controller works.
>>
>> We really should never encounter this.
>>
>> But if we do then I think closest to the truth would be:
>>
>> state->period = UINT_MAX;
>> state->duty_cycle = 0;
>
> I'd say state->period = 1 & state->duty_cycle = 0 is a better
> representation.
But that would suggest the output is configured for an
infinitely high output frequency, but the frequency is
actually 0, the reason why get_state needs to treat a
base_unit val of 0 special at all is to avoid a division
by 0, and in math dividing by 0 gives infinite, isn't
UINT_MAX a better way to represent infinity ?
Regards,
Hans
WARNING: multiple messages have this Message-ID (diff)
From: Hans de Goede <hdegoede@redhat.com>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: linux-pwm@vger.kernel.org,
intel-gfx <intel-gfx@lists.freedesktop.org>,
"Rafael J . Wysocki" <rjw@rjwysocki.net>,
linux-acpi@vger.kernel.org,
Thierry Reding <thierry.reding@gmail.com>,
dri-devel@lists.freedesktop.org,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Mika Westerberg <mika.westerberg@linux.intel.com>,
Len Brown <lenb@kernel.org>
Subject: Re: [PATCH v3 04/15] pwm: lpss: Add range limit check for the base_unit register value
Date: Tue, 7 Jul 2020 19:31:29 +0200 [thread overview]
Message-ID: <1496178b-ce39-9285-ff75-cd39bc0e9aa7@redhat.com> (raw)
In-Reply-To: <20200707073424.w6vd6e4bhl56kosd@pengutronix.de>
Hi,
On 7/7/20 9:34 AM, Uwe Kleine-König wrote:
> On Mon, Jul 06, 2020 at 10:53:08PM +0200, Hans de Goede wrote:
>> Hi,
>>
>> Thank you for your review and sorry for the slow reply.
>
> No problem for me, I didn't hold my breath :-)
>
>>>> diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
>>>> index 43b1fc634af1..80d0f9c64f9d 100644
>>>> --- a/drivers/pwm/pwm-lpss.c
>>>> +++ b/drivers/pwm/pwm-lpss.c
>>>> @@ -97,6 +97,9 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm,
>>>> freq *= base_unit_range;
>>>> base_unit = DIV_ROUND_CLOSEST_ULL(freq, c);
>>>
>>> DIV_ROUND_CLOSEST_ULL is most probably wrong, too. But I didn't spend
>>> the time to actually confirm that.
>>
>> Yes I saw your comment elsewhere that the PWM API defines rounding
>> in a certain direction, but fixing that falls outside of this patch.
>
> Yeah, sure.
>
>> [...]
>> I hope this helps to explain what is going on a bit.
>
> I will try to make sense of that and reply to the patch directly when I
> succeeded.
>
>> ###
>>
>> As for the behavior on base_unit==0 in the get_state method,
>> as mentioned above I wrote that when I did not fully understood
>> how the controller works.
>>
>> We really should never encounter this.
>>
>> But if we do then I think closest to the truth would be:
>>
>> state->period = UINT_MAX;
>> state->duty_cycle = 0;
>
> I'd say state->period = 1 & state->duty_cycle = 0 is a better
> representation.
But that would suggest the output is configured for an
infinitely high output frequency, but the frequency is
actually 0, the reason why get_state needs to treat a
base_unit val of 0 special at all is to avoid a division
by 0, and in math dividing by 0 gives infinite, isn't
UINT_MAX a better way to represent infinity ?
Regards,
Hans
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
WARNING: multiple messages have this Message-ID (diff)
From: Hans de Goede <hdegoede@redhat.com>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: linux-pwm@vger.kernel.org,
intel-gfx <intel-gfx@lists.freedesktop.org>,
"Rafael J . Wysocki" <rjw@rjwysocki.net>,
linux-acpi@vger.kernel.org, dri-devel@lists.freedesktop.org,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Mika Westerberg <mika.westerberg@linux.intel.com>,
Len Brown <lenb@kernel.org>
Subject: Re: [Intel-gfx] [PATCH v3 04/15] pwm: lpss: Add range limit check for the base_unit register value
Date: Tue, 7 Jul 2020 19:31:29 +0200 [thread overview]
Message-ID: <1496178b-ce39-9285-ff75-cd39bc0e9aa7@redhat.com> (raw)
In-Reply-To: <20200707073424.w6vd6e4bhl56kosd@pengutronix.de>
Hi,
On 7/7/20 9:34 AM, Uwe Kleine-König wrote:
> On Mon, Jul 06, 2020 at 10:53:08PM +0200, Hans de Goede wrote:
>> Hi,
>>
>> Thank you for your review and sorry for the slow reply.
>
> No problem for me, I didn't hold my breath :-)
>
>>>> diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
>>>> index 43b1fc634af1..80d0f9c64f9d 100644
>>>> --- a/drivers/pwm/pwm-lpss.c
>>>> +++ b/drivers/pwm/pwm-lpss.c
>>>> @@ -97,6 +97,9 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm,
>>>> freq *= base_unit_range;
>>>> base_unit = DIV_ROUND_CLOSEST_ULL(freq, c);
>>>
>>> DIV_ROUND_CLOSEST_ULL is most probably wrong, too. But I didn't spend
>>> the time to actually confirm that.
>>
>> Yes I saw your comment elsewhere that the PWM API defines rounding
>> in a certain direction, but fixing that falls outside of this patch.
>
> Yeah, sure.
>
>> [...]
>> I hope this helps to explain what is going on a bit.
>
> I will try to make sense of that and reply to the patch directly when I
> succeeded.
>
>> ###
>>
>> As for the behavior on base_unit==0 in the get_state method,
>> as mentioned above I wrote that when I did not fully understood
>> how the controller works.
>>
>> We really should never encounter this.
>>
>> But if we do then I think closest to the truth would be:
>>
>> state->period = UINT_MAX;
>> state->duty_cycle = 0;
>
> I'd say state->period = 1 & state->duty_cycle = 0 is a better
> representation.
But that would suggest the output is configured for an
infinitely high output frequency, but the frequency is
actually 0, the reason why get_state needs to treat a
base_unit val of 0 special at all is to avoid a division
by 0, and in math dividing by 0 gives infinite, isn't
UINT_MAX a better way to represent infinity ?
Regards,
Hans
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
next prev parent reply other threads:[~2020-07-07 17:31 UTC|newest]
Thread overview: 114+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-20 12:17 [PATCH v3 00/15] acpi/pwm/i915: Convert pwm-crc and i915 driver's PWM code to use the atomic PWM API Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-20 12:17 ` [PATCH v3 01/15] ACPI / LPSS: Resume Cherry Trail PWM controller in no-irq phase Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-22 16:03 ` Rafael J. Wysocki
2020-06-22 16:03 ` [Intel-gfx] " Rafael J. Wysocki
2020-06-22 16:03 ` Rafael J. Wysocki
2020-06-20 12:17 ` [PATCH v3 02/15] ACPI / LPSS: Save Cherry Trail PWM ctx registers only once (at activation) Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-22 16:04 ` Rafael J. Wysocki
2020-06-22 16:04 ` [Intel-gfx] " Rafael J. Wysocki
2020-06-22 16:04 ` Rafael J. Wysocki
2020-06-20 12:17 ` [PATCH v3 03/15] pwm: lpss: Fix off by one error in base_unit math in pwm_lpss_prepare() Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-22 7:25 ` Uwe Kleine-König
2020-06-22 7:25 ` [Intel-gfx] " Uwe Kleine-König
2020-06-22 7:25 ` Uwe Kleine-König
2020-06-20 12:17 ` [PATCH v3 04/15] pwm: lpss: Add range limit check for the base_unit register value Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-22 7:35 ` Uwe Kleine-König
2020-06-22 7:35 ` [Intel-gfx] " Uwe Kleine-König
2020-06-22 7:35 ` Uwe Kleine-König
2020-07-06 20:53 ` Hans de Goede
2020-07-06 20:53 ` [Intel-gfx] " Hans de Goede
2020-07-06 20:53 ` Hans de Goede
2020-07-07 7:34 ` Uwe Kleine-König
2020-07-07 7:34 ` [Intel-gfx] " Uwe Kleine-König
2020-07-07 7:34 ` Uwe Kleine-König
2020-07-07 8:04 ` Hans de Goede
2020-07-07 8:04 ` [Intel-gfx] " Hans de Goede
2020-07-07 8:04 ` Hans de Goede
2020-07-07 17:31 ` Hans de Goede [this message]
2020-07-07 17:31 ` [Intel-gfx] " Hans de Goede
2020-07-07 17:31 ` Hans de Goede
2020-07-07 19:09 ` Uwe Kleine-König
2020-07-07 19:09 ` [Intel-gfx] " Uwe Kleine-König
2020-07-07 19:09 ` Uwe Kleine-König
2020-07-07 19:41 ` Hans de Goede
2020-07-07 19:41 ` [Intel-gfx] " Hans de Goede
2020-07-07 19:41 ` Hans de Goede
2020-06-20 12:17 ` [PATCH v3 05/15] pwm: lpss: Use pwm_lpss_apply() when restoring state on resume Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-20 12:17 ` [PATCH v3 06/15] pwm: crc: Fix period / duty_cycle times being off by a factor of 256 Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-20 12:17 ` [PATCH v3 07/15] pwm: crc: Fix off-by-one error in the clock-divider calculations Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-20 12:17 ` [PATCH v3 08/15] pwm: crc: Fix period changes not having any effect Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-20 12:17 ` [PATCH v3 09/15] pwm: crc: Enable/disable PWM output on enable/disable Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-22 7:55 ` Uwe Kleine-König
2020-06-22 7:55 ` [Intel-gfx] " Uwe Kleine-König
2020-06-22 7:55 ` Uwe Kleine-König
2020-07-06 21:03 ` Hans de Goede
2020-07-06 21:03 ` [Intel-gfx] " Hans de Goede
2020-07-06 21:03 ` Hans de Goede
2020-07-07 7:26 ` Uwe Kleine-König
2020-07-07 7:26 ` [Intel-gfx] " Uwe Kleine-König
2020-07-07 7:26 ` Uwe Kleine-König
2020-06-20 12:17 ` [PATCH v3 10/15] pwm: crc: Implement apply() method to support the new atomic PWM API Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-20 12:17 ` [PATCH v3 11/15] pwm: crc: Implement get_state() method Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-22 7:57 ` Uwe Kleine-König
2020-06-22 7:57 ` [Intel-gfx] " Uwe Kleine-König
2020-06-22 7:57 ` Uwe Kleine-König
2020-07-06 21:05 ` Hans de Goede
2020-07-06 21:05 ` [Intel-gfx] " Hans de Goede
2020-07-06 21:05 ` Hans de Goede
2020-07-06 21:05 ` Hans de Goede
2020-07-07 7:24 ` Uwe Kleine-König
2020-07-07 7:24 ` [Intel-gfx] " Uwe Kleine-König
2020-07-07 7:24 ` Uwe Kleine-König
2020-06-20 12:17 ` [PATCH v3 12/15] drm/i915: panel: Add get_vbt_pwm_freq() helper Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-20 12:17 ` [PATCH v3 13/15] drm/i915: panel: Honor the VBT PWM frequency for devs with an external PWM controller Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-20 12:17 ` [PATCH v3 14/15] drm/i915: panel: Honor the VBT PWM min setting " Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-06-20 12:17 ` [PATCH v3 15/15] drm/i915: panel: Use atomic PWM API " Hans de Goede
2020-06-20 12:17 ` [Intel-gfx] " Hans de Goede
2020-06-20 12:17 ` Hans de Goede
2020-07-07 7:50 ` Uwe Kleine-König
2020-07-07 7:50 ` [Intel-gfx] " Uwe Kleine-König
2020-07-07 7:50 ` Uwe Kleine-König
2020-07-07 19:21 ` Hans de Goede
2020-07-07 19:21 ` [Intel-gfx] " Hans de Goede
2020-07-07 19:21 ` Hans de Goede
2020-06-20 12:41 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for acpi/pwm/i915: Convert pwm-crc and i915 driver's PWM code to use the atomic PWM API Patchwork
2020-06-20 13:04 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2020-06-20 14:10 ` [Intel-gfx] ✓ Fi.CI.IGT: " Patchwork
2020-06-30 13:51 ` [PATCH v3 00/15] " Jani Nikula
2020-06-30 13:51 ` [Intel-gfx] " Jani Nikula
2020-06-30 13:51 ` Jani Nikula
2020-06-30 13:51 ` Jani Nikula
2020-07-06 20:53 ` Hans de Goede
2020-07-06 20:53 ` [Intel-gfx] " Hans de Goede
2020-07-06 20:53 ` Hans de Goede
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