linux-kernel - Re: [PATCH v3 21/24] drm/rockchip: dw-mipi-dsi: defer probe if panel is not loaded

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Date:   Fri, 10 Feb 2017 17:27:47 +0000
From:   John Keeping <john@...anate.com>
To:     Sean Paul <seanpaul@...omium.org>
Cc:     Mark Yao <mark.yao@...k-chips.com>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        linux-rockchip@...ts.infradead.org,
        Chris Zhong <zyw@...k-chips.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 21/24] drm/rockchip: dw-mipi-dsi: defer probe if
 panel is not loaded

On Tue, 31 Jan 2017 14:21:17 -0500, Sean Paul wrote:

> On Sun, Jan 29, 2017 at 01:24:41PM +0000, John Keeping wrote:
> > This ensures that the output resolution is known before fbcon loads.
> > 
> > Signed-off-by: John Keeping <john@...anate.com>
> > ---
> > Unchanged in v3
> > Unchanged in v2
> > 
> >  drivers/gpu/drm/rockchip/dw-mipi-dsi.c | 11 +++++++++--
> >  1 file changed, 9 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> > index f5b15377ef85..5bad92e2370e 100644
> > --- a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> > +++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> > @@ -1176,10 +1176,17 @@ static int dw_mipi_dsi_bind(struct device *dev, struct device *master,
> >  
> >  	dsi->dsi_host.ops = &dw_mipi_dsi_host_ops;
> >  	dsi->dsi_host.dev = dev;
> > -	return mipi_dsi_host_register(&dsi->dsi_host);
> > +	ret = mipi_dsi_host_register(&dsi->dsi_host);
> > +	if (!ret && !dsi->panel) {
> > +		mipi_dsi_host_unregister(&dsi->dsi_host);
> > +		drm_encoder_cleanup(&dsi->encoder);
> > +		drm_connector_cleanup(&dsi->connector);  
> 
> Move the host registration up before dw_mipi_dsi_register() to avoid
> having to clean up the encoder and connector?

No, mipi_dsi_host_register() has to be called after the connector is
registered because it is likely to result in a call to
dw_mipi_dsi_host_attach() which attaches a panel to the connector.

> > +		ret = -EPROBE_DEFER;
> > +	}
> >  
> >  err_pllref:
> > -	clk_disable_unprepare(dsi->pllref_clk);
> > +	if (ret)  
> 
> I personally think it's cleaner to explicitly goto in the error conditional (or
> in this case, the defer conditional) and have a return 0; right before the err_*
> labels. Then you don't need to worry about a) checking ret in all of your
> cleanups and b) someone adding code above the labels that you don't intend to
> run.

Agreed.  I'll change this to use a goto if we hit the EPROBE_DEFER case
and keep all the cleanup together.

> > +		clk_disable_unprepare(dsi->pllref_clk);
> >  	return ret;
> >  }