imx8mm eLCDIF clock

[Stefano Babic]

On 21.04.22 14:01, Marek Vasut wrote:
> 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,

+1

Rather, it is not time anymore to get a flickering-free display from 
U-Boot to Linux (it was possible on some SOC before DRM). Just booting 
fast is the best option.

Regards,
Stefano

> 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.




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