From: Paul Cercueil <paul@crapouillou.net>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Rob Herring <robh@kernel.org>,
"Rafael J . Wysocki" <rafael@kernel.org>,
David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
Sam Ravnborg <sam@ravnborg.org>,
list@opendingux.net, linux-kernel@vger.kernel.org,
linux-mips@vger.kernel.org, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH 2/2] gpu/drm: ingenic: Add workaround for disabled drivers
Date: Thu, 05 Aug 2021 22:05:27 +0200 [thread overview]
Message-ID: <3HUDXQ.7RBGD4FUHR2F@crapouillou.net> (raw)
In-Reply-To: <YQw9hjZll4QmYVLX@kroah.com>
Hi Greg,
Le jeu., août 5 2021 at 21:35:34 +0200, Greg Kroah-Hartman
<gregkh@linuxfoundation.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@crapouillou.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
next prev parent reply other threads:[~2021-08-05 20:05 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-05 19:21 [PATCH 0/2] gpu/drm: ingenic: Handle disabled drivers Paul Cercueil
2021-08-05 19:21 ` [PATCH 1/2] drivers core: Export driver_deferred_probe_check_state() Paul Cercueil
2021-08-05 19:34 ` Greg Kroah-Hartman
2021-08-05 19:21 ` [PATCH 2/2] gpu/drm: ingenic: Add workaround for disabled drivers Paul Cercueil
2021-08-05 19:35 ` Greg Kroah-Hartman
2021-08-05 20:05 ` Paul Cercueil [this message]
2021-08-06 10:17 ` Greg Kroah-Hartman
2021-08-06 11:01 ` Paul Cercueil
2021-08-10 9:35 ` Daniel Vetter
2021-08-10 10:33 ` Paul Cercueil
2021-08-10 10:59 ` Daniel Vetter
2021-08-10 11:58 ` Paul Cercueil
2021-08-10 9:47 ` Greg Kroah-Hartman
2021-08-10 10:40 ` Paul Cercueil
2021-08-10 10:52 ` Daniel Vetter
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