[PATCH 2/8] drm/i915/cdclk: Add and use xe2lpd_mdclk_source_sel()

[Gustavo Sousa]

Quoting Gustavo Sousa (2024-03-05 11:40:48-03:00)
>Quoting Matt Roper (2024-03-04 18:58:34-03:00)
>>On Mon, Mar 04, 2024 at 03:30:21PM -0300, Gustavo Sousa wrote:
>>> There will be future changes that rely on the source of the MDCLK. Let's
>>> have xe2lpd_mdclk_source_sel() as the function responsible for reporting
>>> that information.
>>> 
>>> Bspec: 69090
>>> Signed-off-by: Gustavo Sousa <gustavo.sousa at intel.com>
>>> ---
>>>  drivers/gpu/drm/i915/display/intel_cdclk.c | 17 ++++++++++++++++-
>>>  drivers/gpu/drm/i915/i915_reg.h            |  4 +++-
>>>  2 files changed, 19 insertions(+), 2 deletions(-)
>>> 
>>> diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
>>> index 407bd541eb46..bf84bf27213f 100644
>>> --- a/drivers/gpu/drm/i915/display/intel_cdclk.c
>>> +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
>>> @@ -1876,6 +1876,21 @@ static bool cdclk_pll_is_unknown(unsigned int vco)
>>>          return vco == ~0;
>>>  }
>>>  
>>> +static u32 xe2lpd_mdclk_source_sel(struct drm_i915_private *i915)
>>> +{
>>> +        if (DISPLAY_VER(i915) >= 20)
>>> +                return MDCLK_SOURCE_SEL_CDCLK_PLL;
>>> +
>>> +        /*
>>> +         * Earlier display IPs do not provide means of selecting the
>>> +         * MDCLK source, but MDCLK_SOURCE_SEL_CD2XCLK is a nice default,
>>> +         * since it reflects the source used for those and allows
>>> +         * xe2lpd_mdclk_source_sel() to be used in logic that depends on
>>> +         * it.
>>> +         */
>>> +        return MDCLK_SOURCE_SEL_CD2XCLK;
>>
>>At the moment this function only gets called on Xe2 and beyond where the
>>register field exists; if that's going to change soon, then wouldn't it
>>be more natural to just use an early exit to highlight that there's
>>nothing we need to OR into the CDCLK_CTL for earlier platforms?  
>>
>>    /* Not configurable for older platforms; they always use CD2XCLK */
>>    if (DISPLAY_VER(i915) < 20)
>>            return 0;
>>
>>Functionally it's the same, but it feels more intuitive to me.
>>
>>If we aren't expecting to call this from common codepaths that aren't
>>already protected by a display version check, then we could make this a
>>drm_WARN_ON() to assert that we haven't deviated from expected behavior.
>
>Well, the intention here was for this function to serve 2 purposes: (i)
>to give the value of the "MDCLK Source Select" field of CDCLK_CTL and
>also (ii) tell which was the source of the MDCLK for displays pre and
>post (including) Xe2LPD, because we will need that information in
>"drm/i915: Add mdclk_cdclk_ratio to intel_dbuf_state".
>
>I was hoping to do that instead of creating a new enum, but maybe it
>will just cause confusion?
>
>Should we have one function to tell us the source and another for
>giving the value of the register field?

Unless there are objections here, I plan on doing something along these
lines for v2.

--
Gustavo Sousa

>
>--
>Gustavo Sousa
>
>>
>>
>>Matt
>>
>>> +}
>>> +
>>>  static bool cdclk_compute_crawl_and_squash_midpoint(struct drm_i915_private *i915,
>>>                                                      const struct intel_cdclk_config *old_cdclk_config,
>>>                                                      const struct intel_cdclk_config *new_cdclk_config,
>>> @@ -1980,7 +1995,7 @@ static u32 bxt_cdclk_ctl(struct drm_i915_private *i915,
>>>                  val |= BXT_CDCLK_SSA_PRECHARGE_ENABLE;
>>>  
>>>          if (DISPLAY_VER(i915) >= 20)
>>> -                val |= MDCLK_SOURCE_SEL_CDCLK_PLL;
>>> +                val |= xe2lpd_mdclk_source_sel(i915);
>>>          else
>>>                  val |= skl_cdclk_decimal(cdclk);
>>>  
>>> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
>>> index e00557e1a57f..eb953ed1f113 100644
>>> --- a/drivers/gpu/drm/i915/i915_reg.h
>>> +++ b/drivers/gpu/drm/i915/i915_reg.h
>>> @@ -5900,7 +5900,9 @@ enum skl_power_gate {
>>>  #define  CDCLK_FREQ_540                REG_FIELD_PREP(CDCLK_FREQ_SEL_MASK, 1)
>>>  #define  CDCLK_FREQ_337_308                REG_FIELD_PREP(CDCLK_FREQ_SEL_MASK, 2)
>>>  #define  CDCLK_FREQ_675_617                REG_FIELD_PREP(CDCLK_FREQ_SEL_MASK, 3)
>>> -#define  MDCLK_SOURCE_SEL_CDCLK_PLL        REG_BIT(25)
>>> +#define  MDCLK_SOURCE_SEL_MASK                REG_GENMASK(25, 25)
>>> +#define  MDCLK_SOURCE_SEL_CD2XCLK        REG_FIELD_PREP(MDCLK_SOURCE_SEL_MASK, 0)
>>> +#define  MDCLK_SOURCE_SEL_CDCLK_PLL        REG_FIELD_PREP(MDCLK_SOURCE_SEL_MASK, 1)
>>>  #define  BXT_CDCLK_CD2X_DIV_SEL_MASK        REG_GENMASK(23, 22)
>>>  #define  BXT_CDCLK_CD2X_DIV_SEL_1        REG_FIELD_PREP(BXT_CDCLK_CD2X_DIV_SEL_MASK, 0)
>>>  #define  BXT_CDCLK_CD2X_DIV_SEL_1_5        REG_FIELD_PREP(BXT_CDCLK_CD2X_DIV_SEL_MASK, 1)
>>> -- 
>>> 2.44.0
>>> 
>>
>>-- 
>>Matt Roper
>>Graphics Software Engineer
>>Linux GPU Platform Enablement
>>Intel Corporation