Re: [PATCH] video: fbdev: imxfb: Provide a reset mechanism

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On 10/02/16 21:52, Fabio Estevam wrote:
> Hi Tomi,
> 
> On Fri, Jan 29, 2016 at 10:20 AM, Tomi Valkeinen <tomi.valkeinen@ti.com> wrote:
>>
>>
>> On 19/01/16 15:10, Fabio Estevam wrote:
>>> From: Fabio Estevam <fabio.estevam@nxp.com>
>>>
>>> Currently when we boot the kernel on a mx25pdk the LCDC controller
>>> does not show the Linux logo on boot.
>>>
>>> This problem is well explained by Sascha Hauer:
>>>
>>> "Unfortunately this LCD controller does not have an enable bit. The
>>> controller starts directly when the clocks are enabled. If the clocks
>>> are enabled when the controller is not yet programmed with proper
>>> register values then it just goes into some undefined state. What I
>>> suspect is that the clocks already were enabled before driver probe,
>>> presumably by the bootloader, so the controller is already in undefined
>>> state when entering Linux. Now by dis/enabling the ipg clock you
>>> effectively reset the controller. Since you have programmed it with
>>> valid register values in the mean time it starts working after this
>>> reset."
>>>
>>> So do as suggested and force a reset of the LCDC hardware by
>>> enabling and disabling the IPG clock.
>>>
>>> With this change the Linux logo can be seen on boot on a mx25pdk.
>>>
>>> Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
>>> ---
>>>  drivers/video/fbdev/imxfb.c | 15 +++++++++++++++
>>>  1 file changed, 15 insertions(+)
>>
>> Thanks. Queued for 4.5 fixes.
> 
> Still don't see this one applied in Linus nor linux-next tree yet.

I've been a bit preoccupied, but I hope I get to send the pull request
today.

 Tomi


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