Re: [PATCH v12 1/3] drm: rockchip: Add basic drm driver

From: Boris Brezillon <boris.brezillon@free-electrons.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: Mark Yao <mark.yao@rock-chips.com>,
	heiko@sntech.de, David Airlie <airlied@gmail.com>,
	Rob Clark <robdclark@gmail.com>, Rob Herring <robh+dt@kernel.org>,
	Pawel Moll <pawel.moll@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Ian Campbell <ijc+devicetree@hellion.org.uk>,
	Kumar Gala <galak@codeaurora.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	Grant Likely <grant.likely@linaro.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	John Stultz <john.stultz@linaro.org>,
	Rom Lemarchand <romlem@google.com>,
	devicetree@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	linux-api@vger.kernel.org, linux-rockchip@lists.infradead.org,
	dianders@chromium.org, marcheu@chromium.org, dbehr@chromium.org,
	olof@lixom.net, djkurtz@chromium.org, cf@rock-chips.com,
	xxm@rock-chips.com, huangtao@rock-chips.com,
	kever.yang@rock-chips.com, yxj@rock-chips.com, xw@rock-chips.com
Subject: Re: [PATCH v12 1/3] drm: rockchip: Add basic drm driver
Date: Tue, 18 Nov 2014 14:21:30 +0100	[thread overview]
Message-ID: <20141118142130.6c12ab50@bbrezillon> (raw)
In-Reply-To: <20141118083234.GZ25711@phenom.ffwll.local>

Hi Daniel,

On Tue, 18 Nov 2014 09:32:34 +0100
Daniel Vetter <daniel@ffwll.ch> wrote:

> On Tue, Nov 18, 2014 at 04:00:29PM +0800, Mark Yao wrote:
> > From: Mark yao <mark.yao@rock-chips.com>
> > 
> > This patch adds the basic structure of a DRM Driver for Rockchip Socs.
> > 
> > Signed-off-by: Mark Yao <mark.yao@rock-chips.com>
> > Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
> > Acked-by: Daniel Vetter <daniel@ffwll.ch>
> > Reviewed-by: Rob Clark <robdclark@gmail.com>
> > ---
> > Changes in v2:
> > - use the component framework to defer main drm driver probe
> >   until all VOP devices have been probed.
> > - use dma-mapping API with ARM_DMA_USE_IOMMU, create dma mapping by
> >   master device and each vop device can shared the drm dma mapping.
> > - use drm_crtc_init_with_planes and drm_universal_plane_init.
> > - remove unnecessary middle layers.
> > - add cursor set, move funcs to rockchip drm crtc.
> > - use vop reset at first init
> > - reference framebuffer when used and unreference when swap out vop
> > 
> > Changes in v3:
> > - change "crtc->fb" to "crtc->primary-fb"
> > Adviced by Daniel Vetter
> > - init cursor plane with universal api, remove unnecessary cursor set,move 
> > 
> > Changes in v4:
> > Adviced by David Herrmann
> > - remove drm_platform_*() usage, use register drm device directly.
> 
> Minor fixup for that part below.
> 
> [snip]
> 
> > +static int rockchip_drm_bind(struct device *dev)
> > +{
> > +	struct drm_device *drm;
> > +	int ret;
> > +
> > +	drm = drm_dev_alloc(&rockchip_drm_driver, dev);
> > +	if (!drm)
> > +		return -ENOMEM;
> > +
> > +	ret = drm_dev_set_unique(drm, "%s", dev_name(dev));
> > +	if (ret)
> > +		goto err_free;
> 
> Please call rockchip_drm_load here directly and don't put it as the ->load
> function into the driver vtable. The point of the alloc/register split is
> that the driver can be completely set up _before_ we register anything.
> But for backwards compat and historical reasons ->load is called somewhere
> in the middle (so that you could access the minor nodes if needed, since
> some drivers do that).

I tried to do the same in the atmel-hlcdc DRM driver, but I need the
primary drm_minor to register the connectors (see this kernel
backtrace [1]), which means I either initialize the connector in the
wrong place (currently part of the drm load process), or I just can't
call atmel_hlcdc_dc_load before registering the drm device...

Regards,

Boris

[1]http://code.bulix.org/fi7trt-87436

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com