Re: [V2][PATCH] drm: xlnx: zynqmp: release reset to DP controller before accessing DP registers

From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Michal Simek <monstr@monstr.eu>
Cc: Quanyang Wang <quanyang.wang@windriver.com>,
	Hyun Kwon <hyun.kwon@xilinx.com>, David Airlie <airlied@linux.ie>,
	Daniel Vetter <daniel@ffwll.ch>,
	dri-devel@lists.freedesktop.org,
	linux-arm <linux-arm-kernel@lists.infradead.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [V2][PATCH] drm: xlnx: zynqmp: release reset to DP controller before accessing DP registers
Date: Fri, 6 Aug 2021 13:43:37 +0300	[thread overview]
Message-ID: <YQ0SWXvWZ5THf+vM@pendragon.ideasonboard.com> (raw)
In-Reply-To: <CAHTX3d+uZsqevn0+7Lo+z62mk-1+S7n7VuO-QU8Q1Y-gP0Ugyw@mail.gmail.com>

Hi Michale,

On Fri, Aug 06, 2021 at 12:37:07PM +0200, Michal Simek wrote:
> st 24. 3. 2021 v 4:15 odesílatel Laurent Pinchart napsal:
> > On Tue, Mar 23, 2021 at 10:55:01AM +0800, quanyang.wang@windriver.com wrote:
> > > From: Quanyang Wang <quanyang.wang@windriver.com>
> > >
> > > When insmod zynqmp-dpsub.ko after rmmod it, system will hang with the
> > > error log as below:
> > >
> > > root@xilinx-zynqmp:~# insmod zynqmp-dpsub.ko
> > > [   88.391289] [drm] Initialized zynqmp-dpsub 1.0.0 20130509 for fd4a0000.display on minor 0
> > > [   88.529906] Console: switching to colour frame buffer device 128x48
> > > [   88.549402] zynqmp-dpsub fd4a0000.display: [drm] fb0: zynqmp-dpsubdrm frame buffer device
> > > [   88.571624] zynqmp-dpsub fd4a0000.display: ZynqMP DisplayPort Subsystem driver probed
> > > root@xilinx-zynqmp:~# rmmod zynqmp_dpsub
> > > [   94.023404] Console: switching to colour dummy device 80x25
> > > root@xilinx-zynqmp:~# insmod zynqmp-dpsub.ko
> > >       <hang here>
> > >
> > > This is because that in zynqmp_dp_probe it tries to access some DP
> > > registers while the DP controller is still in the reset state. When
> > > running "rmmod zynqmp_dpsub", zynqmp_dp_reset(dp, true) in
> > > zynqmp_dp_phy_exit is called to force the DP controller into the reset
> > > state. Then insmod will call zynqmp_dp_probe to program the DP registers,
> > > but at this moment the DP controller hasn't been brought out of the reset
> > > state yet since the function zynqmp_dp_reset(dp, false) is called later and
> > > this will result the system hang.
> > >
> > > Releasing the reset to DP controller before any read/write operation to it
> > > will fix this issue. And for symmetry, move zynqmp_dp_reset() call from
> > > zynqmp_dp_phy_exit() to zynqmp_dp_remove().
> > >
> > > Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com>
> >
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> 
> Can someone pick this patch?

I have it in my tree with a set of other changes, I intend to send a
pull request today.

-- 
Regards,

Laurent Pinchart