Re: [PATCH] drm: hdlcd: Stop failing atomic disable check

[Liviu Dudau <liviu.dudau@arm.com>]

Hi Robin,

Sorry for the delay in reviewing this patch, I am drowning a bit this
week in meetings :)

On Mon, Feb 25, 2019 at 02:39:13PM +0000, Robin Murphy wrote:
> When __drm_atomic_helper_disable_all() tries to commit the disabled
> state, we end up in hdlcd_crtc_atomic_check() with a mode clock rate
> of 0. If the input clock has a nonzero minimum rate, this fails the
> clk_round_rate() check and prevents the CRTC being torn down cleanly.
> 
> If we're disabling the output, though, then the clock rate should be
> pretty much irrelevant, so skip it in that case. The kerneldoc seems
> to imply that we probably shouldn't be looking at the rest of the
> state anyway if enable=false.
> 
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>

Acked-by: Liviu Dudau <liviu.dudau@arm.com>


I'll pull your patch into my tree but it will be after v5.1-rc1 that
I'll send fixes to airlied.

> ---
> 
> I'm still occasionally trying to get to the bottom of why the HDLCD on
> Juno doesn't work properly with recent upstream EDK2 (the Linux driver
> thinks it's initialised and taken over, but the hardware stays stuck
> displaying the last contents of the EFI framebuffer). I was hoping that
> just unbinding and reprobing the HDLCD/TDA998x drivers might help reset
> things hard enough to start working again, but sadly no...

I think both HDLCD and Mali DP drivers misbehave when the bootloader
enables the device before the Linux driver probes. I'm interested in
sorting this one out and it involves talking to the SMMU as well, so
I'll get in touch with you outside this thread to see how I can
reproduce your EDK2 environment.

Best regards,
Liviu


> 
> Robin.
> 
>  drivers/gpu/drm/arm/hdlcd_crtc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/arm/hdlcd_crtc.c b/drivers/gpu/drm/arm/hdlcd_crtc.c
> index e4d67b70244d..30a0d9570b57 100644
> --- a/drivers/gpu/drm/arm/hdlcd_crtc.c
> +++ b/drivers/gpu/drm/arm/hdlcd_crtc.c
> @@ -193,6 +193,9 @@ static int hdlcd_crtc_atomic_check(struct drm_crtc *crtc,
>  	struct drm_display_mode *mode = &state->adjusted_mode;
>  	long rate, clk_rate = mode->clock * 1000;
>  
> +	if (!state->enable)
> +		return 0;
> +
>  	rate = clk_round_rate(hdlcd->clk, clk_rate);
>  	if (rate != clk_rate) {
>  		/* clock required by mode not supported by hardware */
> -- 
> 2.20.1.dirty
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯

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