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

- From: Tomi Valkeinen \<hidden\>
- Date: 2016-01-29 12:20:47 
- List: linux-fbdev
- Page: https://ratatoskr.run/linux-fbdev/2016/01/13466481
- Thread: https://ratatoskr.run/linux-fbdev/2016/01/13466480/t.md

```text


On 19/01/16 15:10, Fabio Estevam wrote:
> From: Fabio Estevam <redacted>
> 
> 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 <redacted>
> ---
>  drivers/video/fbdev/imxfb.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)

Thanks. Queued for 4.5 fixes.

 Tomi

```

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