linux-kernel - Re: [PATCH v4 2/5] drm: adp: Add Apple Display Pipe driver

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Message-ID: <20250117-bright-passionate-ibis-804a8a@houat>
Date: Fri, 17 Jan 2025 11:23:38 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Sasha Finkelstein <fnkl.kernel@...il.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, 
	Hector Martin <marcan@...can.st>, Sven Peter <sven@...npeter.dev>, 
	Alyssa Rosenzweig <alyssa@...enzweig.io>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Jessica Zhang <quic_jesszhan@...cinc.com>, asahi@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Alyssa Ross <hi@...ssa.is>, Janne Grunau <j@...nau.net>
Subject: Re: [PATCH v4 2/5] drm: adp: Add Apple Display Pipe driver

Hi,

On Thu, Jan 16, 2025 at 07:52:30PM +0100, Sasha Finkelstein wrote:
> On Wed, 15 Jan 2025 at 11:21, Dmitry Baryshkov
> <dmitry.baryshkov@...aro.org> wrote:
> > > +     ret = drm_simple_encoder_init(drm, &adp->encoder, DRM_MODE_ENCODER_DSI);
> >
> > This is being deprecated, please use drm_encoder_init() /
> > drmm_encoder_init() instead.
> 
> I seem to be unable to find any documentation or a mailing list post
> to this effect. If you are referring to this patchset:
> https://patchwork.kernel.org/project/linux-samsung-soc/patch/20200313201744.19773-3-sam@ravnborg.org/
> according to my understanding, it has not been applied.
> In this case, the simple encoder api provides all functionality i need,
> and a replacement would just be a simple encoder, except copied and pasted
> into this driver.

a drmm_encoder_(alloc|init)'d encoder with a NULL funcs pointer is
strictly equivalent and doesn't require any extra infrastructure or work
on your side compared to what you have here.

> > > +static void adp_remove(struct platform_device *pdev)
> > > +{
> > > +     struct device *dev = &pdev->dev;
> > > +     struct drm_device *drm = dev_get_drvdata(dev);
> > > +     struct adp_drv_private *adp = to_adp(drm);
> > > +
> > > +     adp_disable_vblank(adp);
> >
> > Isn't it being helped by the DRM itself? Anyway, I'd suggest moving it
> > after DRM device unregistration and shutdown.
> 
> Not sure i follow, as this call disables generation of vblank interrupts,
> shouldn't it be done before all drm structures are torn down, to prevent
> the interrupt handler from potentially operating on objects that are in
> an invalid state?

Your adp_crtc_atomic_disable() function calls drm_crtc_vblank_off()
already. drm_atomic_helper_shutdown() will call the CRTC disable hook if
relevant, so you're effectively disabling vblank twice here.

Maxime

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