On Tue, Feb 23, 2016 at 04:22:01PM +0530, Thulasimani, Sivakumar wrote:
>
>
> On 2/16/2016 3:35 PM, Ville Syrjälä wrote:
> > On Tue, Feb 16, 2016 at 07:13:05AM +0530, Thulasimani, Sivakumar wrote:
> >>
> >> On 2/12/2016 8:36 PM, 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.
> >> The value stored in SWF06 is the CD Clock VBIOS/GOP sees during boot. so
> >> it just backs up the CD Clock before it optimizes for the available LFP.
> >> if we
> >> are trusting for higher value we should trust it for lower value too.
> >> The OEM might have did this to either reduce max resolution for cheaper
> >> products or might have removed some cooling mechanisms for thinner
> >> designs since we cannot say which of the reasons we should trust the
> >> lower value too.
> >>
> >> now comes to tough part :(, this SWF06 is saved by VBIOS/GOP driver
> >> from intel alone(it is not programmed from VBT),
> >> since GOP driver can be implemented by anyone and
> >> if anyone implements their own GOP driver we cannot be sure if the
> >> value is valid or not. please check if we can check for "Intel GOP driver".
> >> And if "Intel GOP driver" was used during boot, we can trust the value
> >> 100%. i am not sure how this can be done, so i would recommend
> >> trusting the values with clear debug messages as done below already.
> > We definitely need a way to validate the register value before we trust
> > it for lower values. I suppose we might be able to look at bits 31:16
> > since those should store the current cdclk "decimal" value. If that part
> > looks reasonable, we might be able to trust the "max cdclk" bits as well.
> it seems the bits 31:16 are used only by VBIOS and not GOP, so that wont
> help.
> we need to come up with some other method to confirm the value or verify
> if intel gop is loaded. i will get back if i can find such a mechanism.
Oh, that's unfortunate. IIRC we use some other SWF register to check if
something already initialized things in the cdclk sanitation path.
Not sure if the same could be used here.
> >> As mentioned in another thread, this needs to be done for SKL too.
> >> i dont have a SKL system so if no one else can make a patch for it
> >> i will have to share an untested patch for it :).
> > For SKL it seems a bit easier, since it apparently just stores the max
> > cdclk in 10.1 decimal fixed point in bits 10:0. So invalid/uninitialized
> > values would be easier to spot.
> >
> > Hmm. 11 bits and 10.1 fixed point format, I wonder if it's really
> > decimal and not binary fixed point...
> it uses the same value programmed in CDCLK_CTL register.
> i.e 01 0011 0011 1b = 308.57MHz
OK, so binary fixed point. Maybe I should file a bug against bspec to
remove this confusing "decimal" naming scheme from the cdclk stuff...
>
> regards,
> Sivakumar
> >>> 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);
> >>> + }
> >> for the reasons mentioned above, i would favor trusting lower values too.
> >>
> >> regards,
> >> Sivakumar
> >>> +
> >>> + dev_priv->max_cdclk_freq = max_cdclk_freq;
> >>> } else if (IS_CHERRYVIEW(dev)) {
> >>> dev_priv->max_cdclk_freq = 320000;
> >>> } else if (IS_VALLEYVIEW(dev)) {
>
--
Ville Syrjälä
Intel OTC
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