Re: [PATCH 1/2] drm/rockchip: dw_hdmi: Call drm_encoder_cleanup() in error path

Heiko Stübner
2016-03-07T18:56:18Z

Hi Doug,

Am Montag, 7. März 2016, 10:49:53 schrieb Doug Anderson:
> On Mon, Mar 7, 2016 at 9:57 AM, Heiko Stübner <heiko@sntech.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@rock-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@chromium.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).

correct. I don't see the need to duplicate the cleanup (+added infrastructure
to actually get the encoder in unbind) in all instances, if we just define that
the dw_hdmi core takes control of the encoder _after_ it sucessfully bound.

So only if dw_hdmi_bind() fails does the hw-specific instance need to clean up
the encoder it created.

> 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.

that was my reading as well.

Heiko