linux-kernel - Re: [PATCH v4 4/8] drm/mediatek: add support for Mediatek SoC MT2701

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Date:	Thu, 28 Jul 2016 15:17:36 +0800
From:	YT Shen <yt.shen@...iatek.com>
To:	CK Hu <ck.hu@...iatek.com>
CC:	Philipp Zabel <p.zabel@...gutronix.de>,
	<dri-devel@...ts.freedesktop.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	"Mark Rutland" <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"Russell King" <linux@....linux.org.uk>,
	David Airlie <airlied@...ux.ie>,
	"Matthias Brugger" <matthias.bgg@...il.com>,
	Mao Huang <littlecvr@...omium.org>,
	"Bibby Hsieh" <bibby.hsieh@...iatek.com>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-mediatek@...ts.infradead.org>,
	<srv_heupstream@...iatek.com>,
	"Sascha Hauer" <kernel@...gutronix.de>,
	<yingjoe.chen@...iatek.com>, <emil.l.velikov@...il.com>,
	<thierry.reding@...il.com>
Subject: Re: [PATCH v4 4/8] drm/mediatek: add support for Mediatek SoC MT2701

Hi Philipp, CK,

On Thu, 2016-07-28 at 10:07 +0800, CK Hu wrote:
> Hi, YT:
> 
> On Wed, 2016-07-27 at 12:03 +0200, Philipp Zabel wrote:
> > Am Dienstag, den 26.07.2016, 18:42 +0800 schrieb YT Shen:
> > > Hi CK,
> > > 
> > > On Wed, 2016-07-20 at 14:53 +0800, CK Hu wrote:
> > > > Hi, YT:
> > > > 
> > > > Some comments inline.
> > > > 
> > > > On Fri, 2016-07-15 at 18:07 +0800, YT Shen wrote:
> > > > > This patch add support for the Mediatek MT2701 DISP subsystem.
> > > > > There is only one OVL engine in MT2701.
> > > > > 
> > > > > Signed-off-by: YT Shen <yt.shen@...iatek.com>
> > > > > ---
> > > > >  drivers/gpu/drm/mediatek/mtk_disp_ovl.c     |    6 ++++
> > > > >  drivers/gpu/drm/mediatek/mtk_disp_rdma.c    |    6 ++++
> > > > >  drivers/gpu/drm/mediatek/mtk_drm_ddp.c      |   41 +++++++++++++++++++++++++++
> > > > >  drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c |    7 +++++
> > > > >  drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h |    1 +
> > > > >  drivers/gpu/drm/mediatek/mtk_drm_drv.c      |   31 ++++++++++++++++++++
> > > > >  6 files changed, 92 insertions(+)
> > > > > 
> > > > 
> > > > [snip...]
> > > > 
> > > > >  
> > > > >  static const struct of_device_id mtk_ddp_comp_dt_ids[] = {
> > > > > +	{ .compatible = "mediatek,mt2701-disp-ovl",   .data = (void *)MTK_DISP_OVL },
> > > > >  	{ .compatible = "mediatek,mt8173-disp-ovl",   .data = (void *)MTK_DISP_OVL },
> > > > > +	{ .compatible = "mediatek,mt2701-disp-rdma",  .data = (void *)MTK_DISP_RDMA },
> > > > >  	{ .compatible = "mediatek,mt8173-disp-rdma",  .data = (void *)MTK_DISP_RDMA },
> > > > > +	{ .compatible = "mediatek,mt2701-disp-wdma",  .data = (void *)MTK_DISP_WDMA },
> > > > 
> > > > Is WDMA different from MT8173 to MT2701. If they are the same, you need
> > > > not to add compatible of 'mediatek,mt2701-disp-wdma' because use
> > > > 'mediatek,mt8173-disp-wdma' is enough.
> > > Yes, the hardware has differences, so we need add new compatible
> > > 'mt2701-disp-wdma'
> > 
> > It would be nice if you could add a short paragraph to the patch
> > description about what the hardware differences are (probably just
> > changed register layout in most cases).
Thanks for the suggestions, we will add more descriptions in the future.

> 
> If you don't want to add description, you may separate the modification
> of OVL, RDMA, WDMA, PWM to different patch. And you send patch of OVL
> and RDMA first because you have related code modification for these two.
> You temporarily treat WDMA and PWM as MT8173 and it works. And one day
> you need to modify code of WDMA and PWM for MT2701, then you send the
> patch of WDMA and PWM and you need not to add any description because we
> can find out the difference from source code.

The display module connections is shown in mt2701_mtk_ddp_main[] and
mt2701_mtk_ddp_ext[].
OVL -> RDMA -> COLOR -> BLS(pwm) -> DSI
RDMA -> DPI

This patch series mainly focus on DSI support for MT2701 SoC and the
basic functions.  The BLS(pwm) and DPI parts are not included here.

We will remove 'mt2701-disp-wdma'. We didn't implement its driver and it
is unused now.

For the pwm part, we need the device node to establish the display
module connections.  The pwm compatible string is described in
"dt-bindings: pwm: Add MediaTek display PWM bindings" [1] and the
control is implemented in "pwm: Add MediaTek MT2701 display PWM driver
support" [2].

For the dpi part, we need the device node to establish the display
module connections.  The dpi patch will be in another patch series,
split out from "drm/mediatek: fix the wrong pixel clock when resolution
is 4K" [3].


[1] https://patchwork.kernel.org/patch/9222997/
[2] https://patchwork.kernel.org/patch/9223001/
[3] https://patchwork.kernel.org/patch/9249471/ 

Regards,
yt.shen

> 
> > 
> > regards
> > Philipp
> > 
> 
> Regards,
> CK
>