[Intel-gfx] [PATCH v4 04/11] drm/i915: LVDS pixel clock check

[Lukas Wunner]

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