linux-kernel - RE: [PATCH v2 4/8] drm: xlnx: zynqmp_dpsub: Minimize usage of global flag

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Message-ID:
 <MW4PR12MB716563FD80387F0FDC4F146AE6332@MW4PR12MB7165.namprd12.prod.outlook.com>
Date: Wed, 20 Mar 2024 01:12:30 +0000
From: "Klymenko, Anatoliy" <Anatoliy.Klymenko@....com>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
CC: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
	<mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
	<airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, "Simek, Michal"
	<michal.simek@....com>, Andrzej Hajda <andrzej.hajda@...el.com>, Neil
 Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, Jonas
 Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, Rob
 Herring <robh+dt@...nel.org>, Krzysztof Kozlowski
	<krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
	Mauro Carvalho Chehab <mchehab@...nel.org>, "dri-devel@...ts.freedesktop.org"
	<dri-devel@...ts.freedesktop.org>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>, "linux-media@...r.kernel.org"
	<linux-media@...r.kernel.org>
Subject: RE: [PATCH v2 4/8] drm: xlnx: zynqmp_dpsub: Minimize usage of global
 flag

Hi Laurent,

Thank you for the review.

> -----Original Message-----
> From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Sent: Monday, March 18, 2024 5:13 PM
> To: Klymenko, Anatoliy <Anatoliy.Klymenko@....com>
> Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>; Maxime Ripard
> <mripard@...nel.org>; Thomas Zimmermann <tzimmermann@...e.de>; David
> Airlie <airlied@...il.com>; Daniel Vetter <daniel@...ll.ch>; Simek, Michal
> <michal.simek@....com>; Andrzej Hajda <andrzej.hajda@...el.com>; Neil
> Armstrong <neil.armstrong@...aro.org>; Robert Foss <rfoss@...nel.org>; Jonas
> Karlman <jonas@...boo.se>; Jernej Skrabec <jernej.skrabec@...il.com>; Rob
> Herring <robh+dt@...nel.org>; Krzysztof Kozlowski
> <krzysztof.kozlowski+dt@...aro.org>; Conor Dooley <conor+dt@...nel.org>;
> Mauro Carvalho Chehab <mchehab@...nel.org>; dri-
> devel@...ts.freedesktop.org; linux-arm-kernel@...ts.infradead.org; linux-
> kernel@...r.kernel.org; devicetree@...r.kernel.org; linux-
> media@...r.kernel.org
> Subject: Re: [PATCH v2 4/8] drm: xlnx: zynqmp_dpsub: Minimize usage of global
> flag
> 
> Caution: This message originated from an External Source. Use proper caution
> when opening attachments, clicking links, or responding.
> 
> 
> Hi Anatoliy,
> 
> Thank you for the patch.
> 
> On Tue, Mar 12, 2024 at 05:55:01PM -0700, Anatoliy Klymenko wrote:
> > Avoid usage of global zynqmp_dpsub.dma_enabled flag in DPSUB layer
> > context. This flag signals whether the driver runs in DRM CRTC or DRM
> > bridge mode, assuming that all display layers share the same live or
> > non-live mode of operation. Using per-layer mode instead of global
> > flag will siplify future support of the hybrid scenario.
> 
> s/siplify/simplify/
> 
> > Signed-off-by: Anatoliy Klymenko <anatoliy.klymenko@....com>
> > ---
> >  drivers/gpu/drm/xlnx/zynqmp_disp.c | 11 ++++-------
> >  1 file changed, 4 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/xlnx/zynqmp_disp.c
> > b/drivers/gpu/drm/xlnx/zynqmp_disp.c
> > index af851190f447..dd48fa60fa9a 100644
> > --- a/drivers/gpu/drm/xlnx/zynqmp_disp.c
> > +++ b/drivers/gpu/drm/xlnx/zynqmp_disp.c
> > @@ -975,7 +975,7 @@ void zynqmp_disp_layer_disable(struct
> > zynqmp_disp_layer *layer)  {
> >       unsigned int i;
> >
> > -     if (layer->disp->dpsub->dma_enabled) {
> > +     if (layer->mode == ZYNQMP_DPSUB_LAYER_NONLIVE) {
> >               for (i = 0; i < layer->drm_fmt->num_planes; i++)
> >                       dmaengine_terminate_sync(layer->dmas[i].chan);
> >       }
> > @@ -1001,7 +1001,7 @@ void zynqmp_disp_layer_set_format(struct
> > zynqmp_disp_layer *layer,
> >
> >       zynqmp_disp_avbuf_set_format(layer->disp, layer,
> > layer->disp_fmt);
> >
> > -     if (!layer->disp->dpsub->dma_enabled)
> > +     if (layer->mode == ZYNQMP_DPSUB_LAYER_LIVE)
> >               return;
> >
> >       /*
> > @@ -1039,7 +1039,7 @@ int zynqmp_disp_layer_update(struct
> zynqmp_disp_layer *layer,
> >       const struct drm_format_info *info = layer->drm_fmt;
> >       unsigned int i;
> >
> > -     if (!layer->disp->dpsub->dma_enabled)
> > +     if (layer->mode == ZYNQMP_DPSUB_LAYER_LIVE)
> >               return 0;
> 
> The above changes look nice.
> 
> >
> >       for (i = 0; i < info->num_planes; i++) { @@ -1089,7 +1089,7 @@
> > static void zynqmp_disp_layer_release_dma(struct zynqmp_disp *disp,  {
> >       unsigned int i;
> >
> > -     if (!layer->info || !disp->dpsub->dma_enabled)
> > +     if (!layer->info)
> 
> This, however, doesn't seem right, as this function is called unconditionally from
> the remove path. The change below seems weird too.
> If I'm missing something, it should at least be explained in the commit message.
> 

Actually, this whole condition should be removed, as now we're setting layer.info for all types of layers. On top of that, we're setting the number of DMA channels to zero for the live layers, which in turn prevents any DMA channel initialization or release. You are right - that probably should be mentioned explicitly in the commit message. I'll update it.

> >               return;
> >
> >       for (i = 0; i < layer->info->num_channels; i++) { @@ -1132,9
> > +1132,6 @@ static int zynqmp_disp_layer_request_dma(struct zynqmp_disp
> *disp,
> >       unsigned int i;
> >       int ret;
> >
> > -     if (!disp->dpsub->dma_enabled)
> > -             return 0;
> > -
> >       for (i = 0; i < layer->info->num_channels; i++) {
> >               struct zynqmp_disp_layer_dma *dma = &layer->dmas[i];
> >               char dma_channel_name[16];
> >
> 
> --
> Regards,
> 
> Laurent Pinchart

Thank you,
Anatoliy