On Fri, Feb 12, 2016 at 05:06:07PM +0200, ville.syrjala@xxxxxxxxxxxxxxx wrote:
> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>
> Bspec tells us that we can allow cdclk up to 540Mhz on BDW ULX, or
> up to 675 MHz on ULT, bu only if extra cooling is provided. There
> don't seem to be any strap or VBT bits to tells us this however.
>
> But I did spot something potentially relevant in
> VBIOS_GOP_Driver_SWF_Registers.pdf. Apparently VBIOS/GOP can pass
> the max cdclk frequeny in SWF06 to the driver. Let's assume the firmware
> knows what its doing and trust the max cdclk in SWF06 if it's higher
> than the basic limit specified in Bspec. To avoid regressing anything
> let's ignore SWF06 if it indicates a lower limit than Bspec.
>
> Cc: Clint Taylor <clinton.a.taylor@xxxxxxxxx>
> Cc: "Thulasimani, Sivakumar" <sivakumar.thulasimani@xxxxxxxxx>
> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> ---
>
> I'm not at all sure if this is the right way to go about it. Sivakumar,
> since you seem to have some ideas on this maybe you can have a look.
> I'm not aware of any complaints so far that people can't get the cdclk
> as high is they should on specific machines, so not sure if this is really
> even needed.
>
> The other open question is what we should do if the VBIOS limit is
> lower than what we'd expect based on BSpec. Should we still trust it?
> Sadly we can't verify the SWF06 cdclk value in any way since it
> only has two bits and we have four possible cdclk values.
Oh, and I forgot to mention that this is totally untested.
>
> drivers/gpu/drm/i915/intel_display.c | 60 ++++++++++++++++++++++++++++--------
> 1 file changed, 47 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 836bbdc239b6..1d70f6bf2934 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -5407,21 +5407,55 @@ static void intel_update_max_cdclk(struct drm_device *dev)
> dev_priv->max_cdclk_freq = 450000;
> else
> dev_priv->max_cdclk_freq = 337500;
> - } else if (IS_BROADWELL(dev)) {
> + } else if (IS_BROADWELL(dev)) {
> + int bios_max_cdclk_freq, max_cdclk_freq;
> +
> /*
> - * FIXME with extra cooling we can allow
> - * 540 MHz for ULX and 675 Mhz for ULT.
> - * How can we know if extra cooling is
> - * available? PCI ID, VTB, something else?
> + * With extra cooling we can allow 540 MHz for
> + * ULX and 675 Mhz for ULT. Assume VBIOS/GOP
> + * passes that information in SWF06.
> */
> - if (I915_READ(FUSE_STRAP) & HSW_CDCLK_LIMIT)
> - dev_priv->max_cdclk_freq = 450000;
> - else if (IS_BDW_ULX(dev))
> - dev_priv->max_cdclk_freq = 450000;
> - else if (IS_BDW_ULT(dev))
> - dev_priv->max_cdclk_freq = 540000;
> - else
> - dev_priv->max_cdclk_freq = 675000;
> + switch (I915_READ(SWF_ILK(0x06)) & 0x3) {
> + case 0:
> + bios_max_cdclk_freq = 450000;
> + break;
> + case 1:
> + bios_max_cdclk_freq = 540000;
> + break;
> + case 2:
> + bios_max_cdclk_freq = 337500;
> + break;
> + case 3:
> + bios_max_cdclk_freq = 675000;
> + break;
> + }
> +
> + if (I915_READ(FUSE_STRAP) & HSW_CDCLK_LIMIT) {
> + if (WARN_ON(bios_max_cdclk_freq != 450000))
> + bios_max_cdclk_freq = 450000;
> + max_cdclk_freq = 450000;
> + } else if (IS_BDW_ULX(dev_priv)) {
> + if (WARN_ON(bios_max_cdclk_freq > 540000))
> + bios_max_cdclk_freq = 540000;
> + max_cdclk_freq = 450000;
> + } else if (IS_BDW_ULT(dev_priv)) {
> + max_cdclk_freq = 540000;
> + } else {
> + max_cdclk_freq = 675000;
> + }
> +
> + if (bios_max_cdclk_freq > max_cdclk_freq) {
> + DRM_DEBUG_KMS("VBIOS/GOP max cdclk (%d kHz) higher than basic limit (%d kHz), "
> + "assuming extra cooling is present\n",
> + bios_max_cdclk_freq, max_cdclk_freq);
> + max_cdclk_freq = bios_max_cdclk_freq;
> + } else if (bios_max_cdclk_freq < max_cdclk_freq) {
> + DRM_DEBUG_KMS("VBIOS/GOP max cdclk (%d kHz) lower than basic limit (%d kHz), "
> + "ignoring it\n",
> + bios_max_cdclk_freq, max_cdclk_freq);
> + }
> +
> + dev_priv->max_cdclk_freq = max_cdclk_freq;
> } else if (IS_CHERRYVIEW(dev)) {
> dev_priv->max_cdclk_freq = 320000;
> } else if (IS_VALLEYVIEW(dev)) {
> --
> 2.4.10
--
Ville Syrjälä
Intel OTC
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