[Intel-gfx] [PATCH] drm/i915: Update HDMI max TMDS data rate definition for VBT

[Ville Syrjälä]

On Tue, Apr 09, 2019 at 03:46:20PM +0000, Chiou, Cooper wrote:
> Hi Ville,
> 
> The bits is 5-7 means it’s 001x xxxx for 2.97Gbps, and 010x xxxx for 1.65Gbps.
> So correct value should be 2 not 1 for HDMI_MAX_DATA_RATE_297.

No. The bitfield is defined as something:3.

> And HDMI_MAX_DATA_RATE_165 is 4 not 2.
> 
> I checked kernel i915 log and modified VBT to limit HDMI 1.4 from HDMI 2.0 then found this error. And I run CrOS on GLK with changed VBT to validate it. Thanks,
> 
> Best Regards,
> Cooper
> 
> On Apr 9, 2019, at 8:45 PM, Ville Syrjälä <ville.syrjala at linux.intel.com<mailto:ville.syrjala at linux.intel.com>> wrote:
> 
> On Tue, Apr 09, 2019 at 06:07:08PM +0800, Chiou, Cooper wrote:
> VBT version 212 defined HDMI max. bit-rate 2.97Gbps is 0x02 and 1.65Gbps
> is 0x04, so changed HDMI_MAX_DATA_RATE_297/HDMI_MAX_DATA_RATE_165 to map
> correct values
> 
> Eh what? Did someone just change the interpretation of these bits?
> 
> Per VBT BSpec definition in HDMI max. data rate, Bits7-5 is HDMI max. data
> rate 000=Default, 001=2.97Gbps, 010=1.65Gbps,
> 
> Here you're quoting the values we already use...
> 
> so HDMI_MAX_DATA_RATE_297
> should be 2 and HDMI_MAX_DATA_RATE_165 should be 4
> 
> ...but here you're using different values again? Which way is it?
> 
> 
> TEST: Validated PASS on GLK RVP platform
> 
> Cc: Jani Nikula <jani.nikula at intel.com<mailto:jani.nikula at intel.com>>
> Signed-off-by: Chiou, Cooper <cooper.chiou at intel.com<mailto:cooper.chiou at intel.com>>
> ---
> drivers/gpu/drm/i915/intel_vbt_defs.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_vbt_defs.h b/drivers/gpu/drm/i915/intel_vbt_defs.h
> index bf3662ad5fed..e2b8d042912b 100644
> --- a/drivers/gpu/drm/i915/intel_vbt_defs.h
> +++ b/drivers/gpu/drm/i915/intel_vbt_defs.h
> @@ -307,8 +307,8 @@ struct bdb_general_features {
> #define DVO_PORT_MIPID        24                /* 171 */
> 
> #define HDMI_MAX_DATA_RATE_PLATFORM    0            /* 204 */
> -#define HDMI_MAX_DATA_RATE_297        1            /* 204 */
> -#define HDMI_MAX_DATA_RATE_165        2            /* 204 */
> +#define HDMI_MAX_DATA_RATE_297        2            /* 212 */
> +#define HDMI_MAX_DATA_RATE_165        4            /* 212 */
> 
> #define LEGACY_CHILD_DEVICE_CONFIG_SIZE        33
> 
> --
> 2.7.4
> 
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> 
> --
> Ville Syrjälä
> Intel

-- 
Ville Syrjälä
Intel