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Message-Id: <3HUDXQ.7RBGD4FUHR2F@crapouillou.net>
Date: Thu, 05 Aug 2021 22:05:27 +0200
From: Paul Cercueil <paul@...pouillou.net>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Rob Herring <robh@...nel.org>,
"Rafael J . Wysocki" <rafael@...nel.org>,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
Sam Ravnborg <sam@...nborg.org>, list@...ndingux.net,
linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 2/2] gpu/drm: ingenic: Add workaround for disabled drivers
Hi Greg,
Le jeu., août 5 2021 at 21:35:34 +0200, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> a écrit :
> On Thu, Aug 05, 2021 at 09:21:09PM +0200, Paul Cercueil wrote:
>> When the drivers of remote devices (e.g. HDMI chip) are disabled in
>> the
>> config, we want the ingenic-drm driver to be able to probe
>> nonetheless
>> with the other devices (e.g. internal LCD panel) that are enabled.
>>
>> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
>> ---
>> drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 12 ++++++++++++
>> 1 file changed, 12 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
>> b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
>> index d261f7a03b18..5e1fdbb0ba6b 100644
>> --- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
>> +++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
>> @@ -1058,6 +1058,18 @@ static int ingenic_drm_bind(struct device
>> *dev, bool has_components)
>> for (i = 0; ; i++) {
>> ret = drm_of_find_panel_or_bridge(dev->of_node, 0, i, &panel,
>> &bridge);
>> if (ret) {
>> + /*
>> + * Workaround for the case where the drivers for the
>> + * remote devices are not enabled. When that happens,
>> + * drm_of_find_panel_or_bridge() returns -EPROBE_DEFER
>> + * endlessly, which prevents the ingenic-drm driver from
>> + * working at all.
>> + */
>> + if (ret == -EPROBE_DEFER) {
>> + ret = driver_deferred_probe_check_state(dev);
>> + if (ret == -ENODEV || ret == -ETIMEDOUT)
>> + continue;
>> + }
>
> So you are mucking around with devices on other busses within this
> driver? What could go wrong? :(
I'm doing the same thing as everybody else. This is the DRM driver, and
there is a driver for the external HDMI chip which gives us a DRM
bridge that we can obtain from the device tree.
> Please use the existing driver core functionality for this type of
> thing, it is not unique, no need for this function to be called.
I'm not sure you understand what I'm doing here. This driver calls
drm_of_find_panel_or_bridge(), without guarantee that the driver for
the remote device (connected via DT graph) has been enabled in the
kernel config. In that case it will always return -EPROBE_DEFER and the
ingenic-drm driver will never probe.
This patch makes sure that the driver can probe if the HDMI driver has
been disabled in the kernel config, nothing more.
Cheers,
-Paul
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