Re: [PATCH 0/5] drm/vc4: hdmi: Remove CPU hangs, take 2

From: Michael Stapelberg <michael@stapelberg.ch>
To: Maxime Ripard <maxime@cerno.tech>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	Daniel Vetter <daniel.vetter@intel.com>,
	David Airlie <airlied@linux.ie>,
	linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org,
	linux-rpi-kernel@lists.infradead.org,
	Mike Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>,
	Nicolas Saenz Julienne <nsaenz@kernel.org>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 0/5] drm/vc4: hdmi: Remove CPU hangs, take 2
Date: Thu, 23 Sep 2021 09:05:40 +0200	[thread overview]
Message-ID: <CANnVG6mEL+Lzir=K7zBTWVV5zXsdokWCHvsTkM2McGHTO3HEfQ@mail.gmail.com> (raw)
In-Reply-To: <CANnVG6kFC7q_dDDp4rRZsJz=paHKy2STn9127LE=JJOf2kW2TA@mail.gmail.com>

I can confirm that this patch series (applied to linux commit
58e2cf5d794616b84f591d4d1276c8953278ce24) works for me — my Raspberry
Pi 3 still boots fine (without HDMI connected).

Thanks!

On Wed, 22 Sept 2021 at 23:18, Michael Stapelberg <michael@stapelberg.ch> wrote:
>
>
> On Wed, 22 Sept 2021 at 14:54, Maxime Ripard <maxime@cerno.tech> wrote:
>>
>> Hi,
>>
>> Here's another attempt at fixing the complete CPU stall while retrieving the
>> HDMI connector status when the connector is disabled.
>>
>> This was fixed already, but eventually got reverted by Linus due to the same
>> symptom happening in another situation. This was likely (but not confirmed by
>> the reporter) due to the kernel being booted without an HDMI display connected,
>> in which case the firmware won't initialise the HDMI State Machine clock.
>
>
> Sorry for the lack of confirmation: yes, this problem was encountered when no HDMI display was connected.
>
> I’ll try testing your patch series tomorrow.
>
> Thanks for taking care of this!
>
>>
>>
>> This is fixed by patch 3. However, further changes in the clock drivers were
>> needed for clk_set_min_rate to be used, which are patches 1 and 2.
>>
>> Finally, patches 4 and 5 are the original patches that were reverted. Patch 4
>> got a small modification to move the clk_set_min_rate() call before the HSM
>> clock is enabled.
>>
>> Let me know what you think,
>> Maxime
>>
>> Maxime Ripard (5):
>>   clk: bcm-2835: Pick the closest clock rate
>>   clk: bcm-2835: Remove rounding up the dividers
>>   drm/vc4: hdmi: Set a default HSM rate
>>   drm/vc4: hdmi: Move the HSM clock enable to runtime_pm
>>   drm/vc4: hdmi: Make sure the controller is powered in detect
>>
>>  drivers/clk/bcm/clk-bcm2835.c  | 13 ++---
>>  drivers/gpu/drm/vc4/vc4_hdmi.c | 90 ++++++++++++++++++++++++----------
>>  2 files changed, 68 insertions(+), 35 deletions(-)
>>
>> --
>> 2.31.1
>>
>
>
> --
> Best regards,
> Michael

-- 
Best regards,
Michael