Re: [PATCH V2] gpu: drm: tegra: Adjust dsi phy timing

[Thierry Reding <thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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The subject prefix should be "drm/tegra: dsi:". Also make sure to use
the proper case. "dsi" should be "DSI" and "phy" should be "PHY". Also
the DSI PHY is typically referred to as D-PHY, so a better subject would
be:

	drm/tegra: dsi: Adjust D-PHY timing

One more comment below:

On Tue, Dec 02, 2014 at 05:40:23PM -0800, David Ung wrote:
> Fix DSI PHY HS Trail setting on Tegra.
> It is found that HS Trail is off -12% during compliance testing
> 
> Signed-off-by: David Ung <davidu-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/gpu/drm/tegra/mipi-phy.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/tegra/mipi-phy.c b/drivers/gpu/drm/tegra/mipi-phy.c
> index 486d19d..974bc68 100644
> --- a/drivers/gpu/drm/tegra/mipi-phy.c
> +++ b/drivers/gpu/drm/tegra/mipi-phy.c
> @@ -34,7 +34,7 @@ int mipi_dphy_timing_get_default(struct mipi_dphy_timing *timing,
>  	timing->hszero = 145 + 5 * period;
>  	timing->hssettle = 85 + 6 * period;
>  	timing->hsskip = 40;
> -	timing->hstrail = max(8 * period, 60 + 4 * period);
> +	timing->hstrail = 3 * period * 8 + max(8 * period, 60 + 4 * period);
>  	timing->init = 100000;
>  	timing->lpx = 60;
>  	timing->taget = 5 * timing->lpx;

Back when I wrote this code I envisioned that this could eventually be a
generic set of helpers that could be used across different DSI drivers.
As such, mipi_dphy_timing_get_default() obtains the default timings as
given by the D-PHY specification. Therefore you should be adjusting this
within the driver code rather than the default timings. And then make it
something like:

	/* comment explaining why this is needed */
	timing.hstrail += 3 * period * 8;

That said, most of this code is in flux right now, so I probably have to
manually apply the patch. It would still be good to respin with these
comments addressed so that I can adopt the commit message and comment
explaining why this is necessary or what the consequences are.

Thierry

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