linux-kernel - Re: [PATCH 1/2] drm/rockchip: dw_hdmi: Call drm_encoder

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Date:	Mon, 7 Mar 2016 10:49:53 -0800
From:	Doug Anderson <dianders@...omium.org>
To:	Heiko Stübner <heiko@...ech.de>
Cc:	Mark yao <mark.yao@...k-chips.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	John Keeping <john@...ping.me.uk>,
	David Airlie <airlied@...ux.ie>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	Daniel Kurtz <djkurtz@...omium.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/2] drm/rockchip: dw_hdmi: Call drm_encoder_cleanup() in
 error path

Hi,

On Mon, Mar 7, 2016 at 9:57 AM, Heiko Stübner <heiko@...ech.de> wrote:
> Am Montag, 7. März 2016, 09:36:07 schrieb Doug Anderson:
>> Hi,
>>
>> On Mon, Mar 7, 2016 at 12:37 AM, Mark yao <mark.yao@...k-chips.com> wrote:
>> > On 2016年03月05日 20:39, Russell King - ARM Linux wrote:
>> >> On Sat, Mar 05, 2016 at 12:11:16PM +0000, John Keeping wrote:
>> >>> On Fri, Mar 04, 2016 at 03:22:01PM -0800, Douglas Anderson wrote:
>> >>>> The drm_encoder_cleanup() was missing both from the error path of
>> >>>> dw_hdmi_rockchip_bind().  This caused a crash when slub_debug was
>> >>>> enabled and we ended up deferring probe of HDMI at boot.
>> >>>>
>> >>>> This call isn't needed from unbind() because if dw_hdmi_bind() returns
>> >>>> no error then it takes over the job of freeing the encoder (in
>> >>>> dw_hdmi_unbind).
>> >>>>
>> >>>> Signed-off-by: Douglas Anderson <dianders@...omium.org>
>> >>>> ---
>> >>>
>> >>> Does dw_hdmi-imx need a similar change?  I wonder if it would be cleaner
>> >>> to push this into dw_hdmi_bind() if it affects all of the platforms..
>> >>
>> >> I don't think moving it there would make sense - keep the initialisation
>> >> and cleanup together in the same file so that it's contained together.
>> >
>> > I don't like this patch too, initialisation and cleanup not in the same
>> > file looks bad,
>> >
>> > How about:
>> >
>> > drivers/gpu/drm/bridge/dw-hdmi.c
>> > void dw_hdmi_unbind(struct device *dev, struct device *master, void *data)
>> >
>> >         hdmi_writeb(hdmi, ~0, HDMI_IH_MUTE_PHY_STAT0);
>> >
>> > hdmi->connector.funcs->destroy(&hdmi->connector);
>> > -       hdmi->encoder->funcs->destroy(hdmi->encoder);
>> >
>> > drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
>> > static int dw_hdmi_rockchip_bind(struct device *dev, struct device
>> > *master,
>> >
>> > -       return dw_hdmi_bind(dev, master, data, encoder, iores, irq,
>> > plat_data);
>> > +       ret = dw_hdmi_bind(dev, master, data, encoder, iores, irq,
>> > plat_data);
>> > +       if (ret)
>> > +               drm_encoder_cleanup(encoder);
>> > +
>> > +       return ret;
>> >
>> >  }
>> >
>> >  static void dw_hdmi_rockchip_unbind(struct device *dev, struct device
>> >
>> > *master,
>> >
>> >                                     void *data)
>> >
>> >  {
>> >
>> > +       drm_encoder_cleanup(...);
>> >
>> >         return dw_hdmi_unbind(dev, master, data);
>> >
>> >  }
>>
>> That'a a reasonable suggestion in theory.  ...but we run into the same
>> problem I've run into before with the strange relationship between
>> dw_hdmi and its descendants.
>
> I don't think handing off the cleanup responsibility is really in question
> here. I.e. I do believe it should also be fine to expect (as definition) the
> core driver to cleanup the encoder _after_ it sucessfully claimed it in
> dw_hdmi_bind().
>
> We do the same in the rockchip power-domains, handing off the struct clk-
> pointer to the pm_clk stuff (due to the clk-pointer being unique per-device
> nowadays).
>
> So just making sure it is sucessfully handed off should also be ok.

If I understand correctly, that means you'd be OK with the original
patch I posted?  In that case cleanup continues to happen in the main
dw-hdmi.c if dw_hdmi_bind() succeeds and my patch fixes the cleanup
when dw_hdmi_bind() fails (and thus cleanup responsibility was not
handed off).

Also: I noticed that Russell also didn't seem to say that my original
patch was bad.  I think he just said that he didn't like John
Keeping's suggestion.

Please correct any misunderstandings.  Thanks!

-Doug