Re: [PATCH v4 04/11] drm/i915: LVDS pixel clock check

From: Lukas Wunner <lukas@wunner.de>
To: Mika Kahola <mika.kahola@intel.com>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH v4 04/11] drm/i915: LVDS pixel clock check
Date: Fri, 14 Aug 2015 22:10:19 +0200	[thread overview]
Message-ID: <20150814201019.GA6202@wunner.de> (raw)
In-Reply-To: <1439546611-3191-5-git-send-email-mika.kahola@intel.com>

Hi Mika,

On Fri, Aug 14, 2015 at 01:03:24PM +0300, Mika Kahola wrote:
> It is possible the we request to have a mode that has
> higher pixel clock than our HW can support. This patch
> checks if requested pixel clock is lower than the one
> supported by the HW. The requested mode is discarded
> if we cannot support the requested pixel clock.
> 
> This patch applies to LVDS.

The spec lists maximum dot clocks for each connector type.
Here's the spec for IVB for instance (see section 2.3):
https://01.org/sites/default/files/documentation/ivb_ihd_os_vol3_part4.pdf

E.g. for LVDS it's 224 MHz, for DP it's 270 MHz.
If this is identical across all generations (which I haven't checked,
but seems likely), you can use these constant values, which would be
more accurate than just using the same dev_priv->max_cdclk_freq for
all connector types.

Best regards,

Lukas
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/intel-gfx