linux-kernel - Re: [PATCH 0/7] Add DSI display support for TI's Jacinto platforms

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Message-ID: <94e79e4b-ff72-49ba-bcd7-ba69e2296d3b@ti.com>
Date: Mon, 21 Apr 2025 17:48:43 +0530
From: Jayesh Choudhary <j-choudhary@...com>
To: "Kumar, Udit" <u-kumar1@...com>, <nm@...com>, <vigneshr@...com>,
        <devarsht@...com>, <linux-kernel@...r.kernel.org>
CC: <robh@...nel.org>, <krzk+dt@...nel.org>, <conor+dt@...nel.org>,
        <kristo@...nel.org>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 0/7] Add DSI display support for TI's Jacinto platforms

Hello Udit,

On 19/04/25 14:23, Kumar, Udit wrote:
> 
> On 4/11/2025 4:21 PM, Jayesh Choudhary wrote:
>> Hello All,
>>
>> This series adds the dts support to enable DSI on 3 platforms for TI 
>> SoCs:
>> - J784S4-EVM
>> - J721S2-EVM
>> - AM68-SK
>>
>> [..]
>>
>> NOTE: For higher resolutions, we need bigger CMA region.
>> But for validation, the default value is enough.
> 
> I am not sure , how DSS uses CMA region
> 

The framebuffers for dss are allocated from cma-pool.
By default the cma-region is of 32MiB that is shared by various peripherals.

1920x1080 requires ~16MiB of CMA but sometimes due to fragmentation,
we cannot get even this much for framebuffer and memory is not allocated 
resulting in display failures.

And large resolutions like 4k@...ps require ~64MiB straight away.
So it is better to reserve appropriate CMA region.

Thanks
Jayesh

> 
>> I am posting another series to add CMA region to Jacinto platforms
>> similar to Sitara family soon:
>> <https://lore.kernel.org/all/20240613150902.2173582-1-devarsht@ti.com/>
>>
>> Jayesh Choudhary (5):
>>    arm64: dts: ti: k3-j784s4-j742s2-main-common: add DSI & DSI PHY
>>    arm64: dts: ti: k3-j784s4-j742s2-evm-common: Enable DisplayPort-1
>>    arm64: dts: ti: k3-j721s2-common-proc-board: Add main_i2c4 instance
>>    arm64: dts: ti: k3-j721s2-common-proc-board: Enable DisplayPort-1
>>    arm64: dts: ti: k3-am68-sk: Enable DSI on DisplayPort-0
>>
>> Rahul T R (2):
>>    arm64: dts: ti: k3-j721s2-main: add DSI & DSI PHY
>>    arm64: dts: ti: k3-j721s2-som-p0: add DSI to eDP
>>
>>   .../boot/dts/ti/k3-am68-sk-base-board.dts     |  96 ++++++++++++++
>>   .../dts/ti/k3-j721s2-common-proc-board.dts    | 116 +++++++++++++++++
>>   arch/arm64/boot/dts/ti/k3-j721s2-main.dtsi    |  37 ++++++
>>   arch/arm64/boot/dts/ti/k3-j721s2-som-p0.dtsi  |  52 ++++++++
>>   .../dts/ti/k3-j784s4-j742s2-evm-common.dtsi   | 117 +++++++++++++++++-
>>   .../dts/ti/k3-j784s4-j742s2-main-common.dtsi  |  37 ++++++
>>   6 files changed, 454 insertions(+), 1 deletion(-)
>>