Re: [Linux-stm32] [PATCH v3 3/5] ARM: dts: stm32: enable ltdc binding with ili9341 on stm32429-disco board

From: Benjamin GAIGNARD <benjamin.gaignard@st.com>
To: dillon min <dillon.minfei@gmail.com>,
	Alexandre TORGUE <alexandre.torgue@st.com>
Cc: "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>, Daniel Vetter <daniel@ffwll.ch>,
	Dave Airlie <airlied@linux.ie>,
	Linus Walleij <linus.walleij@linaro.org>,
	linux-clk <linux-clk@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"open list:DRM PANEL DRIVERS" <dri-devel@lists.freedesktop.org>,
	"linux-stm32@st-md-mailman.stormreply.com" 
	<linux-stm32@st-md-mailman.stormreply.com>,
	Stephen Boyd <sboyd@kernel.org>, Rob Herring <robh+dt@kernel.org>,
	"thierry.reding@gmail.com" <thierry.reding@gmail.com>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	"Sam Ravnborg" <sam@ravnborg.org>,
	Michael Turquette <mturquette@baylibre.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [Linux-stm32] [PATCH v3 3/5] ARM: dts: stm32: enable ltdc binding with ili9341 on stm32429-disco board
Date: Fri, 15 May 2020 08:31:54 +0000	[thread overview]
Message-ID: <818b93b4-4431-8338-cd90-ed125ecac615@st.com> (raw)
In-Reply-To: <CAL9mu0Jt_xwo5pJfcx6G3grBuOaxLXvakpEjiB4gV3=bkiq2fg@mail.gmail.com>


On 5/14/20 3:07 PM, dillon min wrote:
> Hi Alexandre,
>
> On Thu, May 14, 2020 at 8:53 PM Alexandre Torgue
> <alexandre.torgue@st.com> wrote:
>>
>>
>> On 5/14/20 10:24 AM, Linus Walleij wrote:
>>> On Tue, May 12, 2020 at 9:04 AM <dillon.minfei@gmail.com> wrote:
>>>
>>>> From: dillon min <dillon.minfei@gmail.com>
>>>>
>>>> Enable the ltdc & ili9341 on stm32429-disco board.
>>>>
>>>> Signed-off-by: dillon min <dillon.minfei@gmail.com>
>>> This mostly looks good but...
>>>
>>>> +&spi5 {
>>>> +       status = "okay";
>>>> +       pinctrl-0 = <&spi5_pins>;
>>>> +       pinctrl-names = "default";
>>>> +       #address-cells = <1>;
>>>> +       #size-cells = <0>;
>>>> +       cs-gpios = <&gpioc 2 GPIO_ACTIVE_LOW>;
>>>> +       dmas = <&dma2 3 2 0x400 0x0>,
>>>> +              <&dma2 4 2 0x400 0x0>;
>>>> +       dma-names = "rx", "tx";
>>> These DMA assignments seem to be SoC things and should
>>> rather be in the DTS(I) file where &spi5 is defined, right?
>>> stm32f429.dtsi I suppose?
>> I agree with Linus, DMA have to be defined in SoC dtsi. And if a board
>> doesn't want to use it, we use the "delete-property".
> Yes, will move to Soc dtsi in next submits.
>
> i'm working on write a v4l2-m2m driver for dma2d of stm32 to support
> pixel conversion
> alpha blending between foreground and background graphics.
>
> as you know, some soc's engineer trying to add this function to drm system.
>
> do you know st's planning about soc's hardware accelerator driver on stm32mp?
> such as chrom-art, will add to drm subsystem via ioctl to access, or to v4l2,
On stm32mp we do not plan to use chrom-art in drm or v4l2 because it 
does fit
with userland way of working. We use the GPU to do conversion, scaling, 
blending
and composition in only one go.
As explain here [1] DRM subsytem it isn't a solution and v4l2-m2m isn't 
used in any
mainline compositors like Weston or android surfaceflinger.

Benjamin

[1] 
https://www.phoronix.com/scan.php?page=news_item&px=Linux-DRM-No-2D-Accel-API
>
> thanks.
>
>>> It is likely the same no matter which device is using spi5.
>>>
>>> Yours,
>>> Linus Walleij
>>>
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