Re: [PATCH v3] drm/i915/dmc: Create debugfs entry for dc6 counter

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 04 Mar 2025, Imre Deak <imre.deak@intel.com> wrote:
> On Tue, Mar 04, 2025 at 12:53:19AM +0530, Mohammed Thasleem wrote:
>> Starting from MTL we don't have a platform agnostic way to validate
>> DC6 state due to dc6 counter has been removed to validate DC state.
>> 
>> The goal is to validate that the display HW can reach the DC6 power
>> state. There is no HW DC6 residency counter (and there wasn't such
>> a counter earlier either), so an alternative way is required. According
>> to the HW team the display driver has programmed everything correctly in
>> order to allow the DC6 power state if the DC5 power state is reached
>> (indicated by the HW DC5 residency counter incrementing) and DC6 is
>> enabled by the driver.
>> 
>> Driver could take a snapshot of the DC5 residency counter right
>> after it enables DC6 (dc5_residency_start) and increment the SW
>> DC6 residency counter right before it disables DC6 or when user space
>> reads the DC6 counter. So the driver would update the counter at these
>> two points in the following way:
>> dc6_residency_counter += dc5_current_count - dc5_start_count
>> 
>> v2: Update the discription. (Imre)
>>     Read dc5 count during dc6 enable and disable then and update
>>     dc6 residency counter. (Imre)
>>     Remove variable from dmc structure. (Jani)
>>     Updated the subject title.
>> v3: Add i915_power_domains lock to updated dc6 count in debugfs. (Imre)
>>     Use flags to check dc6 enable/disable states. (Imre)
>>     Move the display version check and counter read/update to
>>     a helper. (Imre)
>>     Resize the variable length. (Rodrigo)
>>     Use old dc6 debugfs entry for every platform. (Rodrigo)
>> 
>> Signed-off-by: Mohammed Thasleem <mohammed.thasleem@intel.com>
>> ---
>>  .../gpu/drm/i915/display/intel_display_core.h |  2 ++
>>  .../i915/display/intel_display_power_well.c   | 26 +++++++++++++++++++
>>  .../i915/display/intel_display_power_well.h   |  1 +
>>  drivers/gpu/drm/i915/display/intel_dmc.c      | 21 ++++++++++++---
>>  4 files changed, 47 insertions(+), 3 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/display/intel_display_core.h b/drivers/gpu/drm/i915/display/intel_display_core.h
>> index 554870d2494b..1608268bd9e2 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display_core.h
>> +++ b/drivers/gpu/drm/i915/display/intel_display_core.h
>> @@ -490,6 +490,8 @@ struct intel_display {
>>  
>>  		/* perform PHY state sanity checks? */
>>  		bool chv_phy_assert[2];
>> +		unsigned int dc6_count;
>
> I think it's better to use dc6_allowed_count as Rodrigo suggested, not
> regarding it as a counter for actual DC6 transitions.
>
>> +		unsigned int dc5_start_count;
>>  	} power;
>>  
>>  	struct {
>> diff --git a/drivers/gpu/drm/i915/display/intel_display_power_well.c b/drivers/gpu/drm/i915/display/intel_display_power_well.c
>> index 5b60db597329..8478e687abb7 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display_power_well.c
>> +++ b/drivers/gpu/drm/i915/display/intel_display_power_well.c
>> @@ -17,6 +17,7 @@
>>  #include "intel_dkl_phy.h"
>>  #include "intel_dkl_phy_regs.h"
>>  #include "intel_dmc.h"
>> +#include "intel_dmc_regs.h"
>>  #include "intel_dmc_wl.h"
>>  #include "intel_dp_aux_regs.h"
>>  #include "intel_dpio_phy.h"
>> @@ -728,6 +729,22 @@ void gen9_sanitize_dc_state(struct intel_display *display)
>>  	power_domains->dc_state = val;
>>  }
>>  
>> +void update_dc6_count(struct intel_display *display, bool dc6_en_dis)
>
> Maybe rename dc6_en_dis to start_tracking?
>
> As Jani suggested the function should be in intel_dmc.c

Well, maybe.

I think the DMC register read should be in intel_dmc.c.

But maybe the display->power.* handling should be in
intel_display_power(_well).c?

IOW, make the functions and interfaces make sense for both. Now there's
no logic in the division.


BR,
Jani.

-- 
Jani Nikula, Intel