From: "james qian wang (Arm Technology China)" <james.qian.wang@arm.com>
To: Brian Starkey <Brian.Starkey@arm.com>
Cc: Mihail Atanassov <Mihail.Atanassov@arm.com>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
David Airlie <airlied@linux.ie>,
Liviu Dudau <Liviu.Dudau@arm.com>,
Russell King <linux@armlinux.org.uk>,
Maxime Ripard <mripard@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
nd <nd@arm.com>, Sean Paul <sean@poorly.run>
Subject: Re: [RFC,3/3] drm/komeda: Allow non-component drm_bridge only endpoints
Date: Fri, 18 Oct 2019 06:38:59 +0000 [thread overview]
Message-ID: <20191018063851.GA18702@jamwan02-TSP300> (raw)
In-Reply-To: <20191017104812.6qpuzoh5bx5i2y3m@DESKTOP-E1NTVVP.localdomain>
On Thu, Oct 17, 2019 at 10:48:12AM +0000, Brian Starkey wrote:
> On Thu, Oct 17, 2019 at 10:21:03AM +0000, james qian wang (Arm Technology China) wrote:
> > On Thu, Oct 17, 2019 at 08:20:56AM +0000, Brian Starkey wrote:
> > > On Thu, Oct 17, 2019 at 03:07:59AM +0000, james qian wang (Arm Technology China) wrote:
> > > > On Wed, Oct 16, 2019 at 04:22:07PM +0000, Brian Starkey wrote:
> > > > >
> > > > > If James is strongly against merging this, maybe we just swap
> > > > > wholesale to bridge? But for me, the pragmatic approach would be this
> > > > > stop-gap.
> > > > >
> > > >
> > > > This is a good idea, and I vote +ULONG_MAX :)
> > > >
> > > > and I also checked tda998x driver, it supports bridge. so swap the
> > > > wholesale to brige is perfect. :)
> > > >
> > >
> > > Well, as Mihail wrote, it's definitely not perfect.
> > >
> > > Today, if you rmmod tda998x with the DPU driver still loaded,
> > > everything will be unbound gracefully.
> > >
> > > If we swap to bridge, then rmmod'ing tda998x (or any other bridge
> > > driver the DPU is using) with the DPU driver still loaded will result
> > > in a crash.
> >
> > I haven't read the bridge code, but seems this is a bug of drm_bridge,
> > since if the bridge is still in using by others, the rmmod should fail
> >
>
> Correct, but there's no fix for that today. You can also take a look
> at the thread linked from Mihail's cover letter.
>
> > And personally opinion, if the bridge doesn't handle the dependence.
> > for us:
> >
> > - add such support to bridge
>
> That would certainly be helpful. I don't know if there's consensus on
> how to do that.
>
> > or
> > - just do the insmod/rmmod in correct order.
> >
> > > So, there really are proper benefits to sticking with the component
> > > code for tda998x, which is why I'd like to understand why you're so
> > > against this patch?
> > >
> >
> > This change handles two different connectors in komeda internally, compare
> > with one interface, it increases the complexity, more risk of bug and more
> > cost of maintainance.
> >
>
> Well, it's only about how to bind the drivers - two different methods
> of binding, not two different connectors. I would argue that carrying
> our out-of-tree patches to support both platforms is a larger
> maintenance burden.
>
> Honestly this looks like a win-win to me. We get the superior approach
> when its supported, and still get to support bridges which are more
> common.
>
My consideration is: if we support both link methods, we may suffering
- 1. bridge reference cnt problem
- 2. maintance two link methods.
the 1) seems unavoidable, so swap all to bridage at least can avoid
the pain of 2). that's why I thought your idea "swap all to bridage"
is good.
Thanks
James.
> As/when improvements are made to the bridge code we can remove the
> component bits and not lose anything.
>
> > So my suggestion is keeping on one single interface in komeda, no
> > matter it is bridge or component, but I'd like it only one, but not
> > them both in komeda.
>
> If we can put the effort into fixing bridges then I guess that's the
> best approach for everyone :-) Might not be easy though!
>
> -Brian
>
> >
> > Thanks
> > James
> >
> > > Thanks,
> > > -Brian
next prev parent reply other threads:[~2019-10-18 6:39 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-04 14:34 [PATCH 0/3] drm/komeda: Support for drm_bridge endpoints Mihail Atanassov
2019-10-04 14:34 ` [PATCH 1/3] drm/komeda: Consolidate struct komeda_drv allocations Mihail Atanassov
2019-10-04 14:34 ` [PATCH 2/3] drm/komeda: Memory manage struct komeda_drv in probe/remove Mihail Atanassov
2019-10-04 14:34 ` [RFC PATCH 3/3] drm/komeda: Allow non-component drm_bridge only endpoints Mihail Atanassov
2019-10-09 5:54 ` [RFC,3/3] " james qian wang (Arm Technology China)
2019-10-16 15:51 ` Mihail Atanassov
2019-10-16 16:22 ` Brian Starkey
2019-10-17 3:07 ` james qian wang (Arm Technology China)
2019-10-17 8:20 ` Brian Starkey
2019-10-17 10:21 ` james qian wang (Arm Technology China)
2019-10-17 10:48 ` Brian Starkey
2019-10-17 11:41 ` Russell King - ARM Linux admin
2019-10-18 6:57 ` james qian wang (Arm Technology China)
2019-10-18 9:12 ` Brian Starkey
2019-10-22 8:42 ` Daniel Vetter
2019-10-22 8:48 ` Russell King - ARM Linux admin
2019-10-22 8:50 ` Daniel Vetter
2019-10-22 14:42 ` Russell King - ARM Linux admin
2019-10-22 14:53 ` Russell King - ARM Linux admin
2019-10-24 8:03 ` Mihail Atanassov
2019-10-24 5:21 ` james qian wang (Arm Technology China)
2019-10-18 6:38 ` james qian wang (Arm Technology China) [this message]
2019-10-18 11:01 ` Mihail Atanassov
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