imx8mm eLCDIF clock

[Marek Vasut]

On 4/21/22 13:54, Tommaso Merciai wrote:
> On Thu, Apr 21, 2022 at 01:20:58PM +0200, Marek Vasut wrote:
>> On 4/21/22 13:14, Adam Ford wrote:
>>> On Thu, Apr 21, 2022 at 5:29 AM Tommaso Merciai
>>> <tommaso.merciai at amarulasolutions.com> wrote:
>>>>
>>>> On Thu, Apr 21, 2022 at 08:48:05AM +0200, Tommaso Merciai wrote:
>>>>
>>>> + Fabio
>>>> + Tim
>>>> + Michael
>>>> + Marek
>>>> + Adam
>>>>
>>>>> Hi,
>>>>> I'm working on drivers/clk/imx/clk-imx8mm.c to port and bring up eLCDIF
>>>>> clocks. After port all necessary clocks needed by eLCDIF I found that
>>>>> IMX8MM_VIDEO_PLL1 clock is not enabled and need the clk_enable to enable
>>>>> it at the end of the clk-imx8mm probe:
>>>>>
>>>>> struct clk *clkp;
>>>>>
>>>>> clk_get_by_id(IMX8MM_VIDEO_PLL1, &clkp);
>>>>> clk_set_rate(clkp, 594000000UL);
>>>>> clk_enable(clkp);
>>>>>
>>>>> What do you think about this solution?
>>>>> There is a more standard way to do this?
>>>>> I'm missing somethings?
>>>
>>> I think the LCD driver should request the clock and clock rate based
>>> on settings the device tree.  However, I think the bigger issues is
>>> that you might run into issues with the lack of a disp-blkctrl driver.
>>> Marek enable the GPC driver fairly recently, but the blkctrl driver
>>> will be needed to enable the LCD and DSI portions or the system may
>>> hang.
>>
>> Just boot quickly and init the graphics pipeline in Linux ?
> 
> Hi Marek,
> Thanks for your feedback. You think make no sense to enable support
> for the graphics pipeline at U-Boot level? Some customers want this
> feature for that I think is better to have support for that.
> What do you think about?

I think it makes no sense to duplicate graphics pipeline in U-Boot.

Just boot quickly enough and bring the graphics pipeline in Linux, then 
maintain one copy of all the drivers involved in the pipeline (scanout 
engine, GPCs, block controllers, bridge drivers, panel drivers). Also, 
you won't have to deal with the display pipeline handoff from U-Boot to 
Linux, which incurs flicker.