[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <b49a242f-dc85-171d-1f0c-93b9099712a3@i2se.com>
Date: Mon, 14 Nov 2022 01:48:14 +0100
From: Stefan Wahren <stefan.wahren@...e.com>
To: Maxime Ripard <maxime@...no.tech>, David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
Thomas Zimmermann <tzimmermann@...e.de>,
Maxime Ripard <mripard@...nel.org>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Emma Anholt <emma@...olt.net>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
Marc Kleine-Budde <mkl@...gutronix.de>
Subject: Re: [PATCH 1/2] drm/vc4: hdmi: Enforce the minimum rate at
runtime_resume
Am 11.11.22 um 22:08 schrieb Stefan Wahren:
> Hi Maxime,
>
> Am 29.09.22 um 11:21 schrieb Maxime Ripard:
>> This is a revert of commit fd5894fa2413 ("drm/vc4: hdmi: Remove clock
>> rate initialization"), with the code slightly moved around.
>>
>> It turns out that we can't downright remove that code from the driver,
>> since the Pi0-3 and Pi4 are in different cases, and it only works for
>> the Pi4.
>>
>> Indeed, the commit mentioned above was relying on the RaspberryPi
>> firmware clocks driver to initialize the rate if it wasn't done by the
>> firmware. However, the Pi0-3 are using the clk-bcm2835 clock driver that
>> wasn't doing this initialization. We therefore end up with the clock not
>> being assigned a rate, and the CPU stalling when trying to access a
>> register.
>>
>> We can't move that initialization in the clk-bcm2835 driver, since the
>> HSM clock we depend on is actually part of the HDMI power domain, so any
>> rate setup is only valid when the power domain is enabled. Thus, we
>> reinstated the minimum rate setup at runtime_suspend, which should
>> address both issues.
>>
>> Link:
>> https://lore.kernel.org/dri-devel/20220922145448.w3xfywkn5ecak2et@pengutronix.de/
>> Fixes: fd5894fa2413 ("drm/vc4: hdmi: Remove clock rate initialization")
>> Reported-by: Marc Kleine-Budde <mkl@...gutronix.de>
>> Signed-off-by: Maxime Ripard <maxime@...no.tech>
>> ---
>> drivers/gpu/drm/vc4/vc4_hdmi.c | 9 +++++++++
>> 1 file changed, 9 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c
>> b/drivers/gpu/drm/vc4/vc4_hdmi.c
>> index 199bc398817f..2e28fe16ed5e 100644
>> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
>> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
>> @@ -2891,6 +2891,15 @@ static int vc4_hdmi_runtime_resume(struct
>> device *dev)
>> u32 __maybe_unused value;
>> int ret;
>> + /*
>> + * The HSM clock is in the HDMI power domain, so we need to set
>> + * its frequency while the power domain is active so that it
>> + * keeps its rate.
>> + */
>> + ret = clk_set_min_rate(vc4_hdmi->hsm_clock, HSM_MIN_CLOCK_FREQ);
>> + if (ret)
>> + return ret;
>> +
>
> unfortunately this breaks X on Raspberry Pi 4 in Linux 6.0.5
> (multi_v7_defconfig + LPAE). Today i saw this report [1] and bisected
> the issue down to this patch. Shame on me that i only tested this
> patch with Rpi 3B+ :-(
Looks like "drm/vc4: hdmi: Fix HSM clock too low on Pi4" addresses this
issue ...
>
> Best regards
>
> [1] - https://bugzilla.suse.com/show_bug.cgi?id=1205259
>
>> ret = clk_prepare_enable(vc4_hdmi->hsm_clock);
>> if (ret)
>> return ret;
>>
Powered by blists - more mailing lists