linux-kernel - Re: [PATCH v2 1/7] gpu: ipu-di: Add ipu_di_adjust

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Date:	Fri, 19 Dec 2014 12:07:04 +0100
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Steve Longerbeam <slongerbeam@...il.com>
Cc:	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-fbdev@...r.kernel.org, David Airlie <airlied@...ux.ie>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Fabio Estevam <fabio.estevam@...escale.com>,
	Shawn Guo <shawn.guo@...aro.org>,
	Denis Carikli <denis@...rea.com>,
	Jiada Wang <jiada_wang@...tor.com>,
	Deepak Das <deepak_das@...tor.com>,
	Steve Longerbeam <steve_longerbeam@...tor.com>
Subject: Re: [PATCH v2 1/7] gpu: ipu-di: Add ipu_di_adjust_videomode()

Hi Steve,

Am Donnerstag, den 18.12.2014, 18:00 -0800 schrieb Steve Longerbeam:
> From: Jiada Wang <jiada_wang@...tor.com>
> 
> On some monitors, high resolution modes are not working, exhibiting
> pixel column truncation problems (for example, 1280x1024 displays as
> 1280x1022).
> 
> The function ipu_di_adjust_videomode() aims to fix these issues by
> adjusting a passed videomode to IPU restrictions. The function can
> be called from the drm_crtc_helper_funcs->mode_fixup() methods.
> 
> Signed-off-by: Jiada Wang <jiada_wang@...tor.com>
> Signed-off-by: Deepak Das <deepak_das@...tor.com>
> Signed-off-by: Steve Longerbeam <steve_longerbeam@...tor.com>
> ---
>  drivers/gpu/ipu-v3/ipu-di.c |   29 +++++++++++++++++++++++++++++
>  include/video/imx-ipu-v3.h  |    2 ++
>  2 files changed, 31 insertions(+)
> 
> diff --git a/drivers/gpu/ipu-v3/ipu-di.c b/drivers/gpu/ipu-v3/ipu-di.c
> index c490ba4..46f9570 100644
> --- a/drivers/gpu/ipu-v3/ipu-di.c
> +++ b/drivers/gpu/ipu-v3/ipu-di.c
> @@ -511,6 +511,35 @@ static void ipu_di_config_clock(struct ipu_di *di,
>  		clk_get_rate(di->clk_di_pixel) / (clkgen0 >> 4));
>  }
>  
> +/*
> + * This function is called to adjust a video mode to IPU restrictions.
> + * It is meant to be called from drm crtc mode_fixup() methods.
> + */
> +int ipu_di_adjust_videomode(struct ipu_di *di, struct videomode *mode)
> +{
> +	u32 diff;
> +
> +	if (mode->vfront_porch >= 2)
> +		return 0;
> +
> +	diff = 2 - mode->vfront_porch;
> +
> +	if (mode->vback_porch >= diff) {
> +		mode->vfront_porch = 2;
> +		mode->vback_porch -= diff;

Should we also add

	else if (mode->vback_porch >= 1 && mode->vsync_len > 1) {
		mode->vback_porch--;
		mode->vsync_len--;

here and maybe move the two "mode->vback_porch = 2" to a single place
below the conditional statement?

> +	} else if (mode->vsync_len > diff) {
> +		mode->vfront_porch = 2;
> +		mode->vsync_len = mode->vsync_len - diff;

Why use "vback_porch -= diff" above, but not "vsync_len -= diff" here?

> +	} else {
> +		dev_warn(di->ipu->dev, "failed to adjust videomode\n");
> +		return -EINVAL;
> +	}
> +
> +	dev_warn(di->ipu->dev, "videomode adapted for IPU restrictions\n");

Since we can return the adjusted mode to userspace now, I think this
should be dev_dbg.

regards
Philipp

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