Re: [v2] drm/i915/dmc: Create debugfs entry for dc6 counter

["Almahallawy, Khaled" <khaled.almahallawy@intel.com>]

On Wed, 2025-02-12 at 17:19 +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.

Historically speaking, when it comes to debugging DC6 issues and
involve all other teams, the communication between Punit and DE is the
sure way to prove display is innocent especially starting from MTL.
Latest in PTL HSD:14023469804

Trace of PM_REQ_DBG/PM_RSP_DBG registers normally is the first step
needed to shows the comms between Punit/DE and LTR configs. 

So, can we cook something with these register to follow the BKM of
debugging DC issues. 

Thanks
Khaled


> 
> 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.
> 
> 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   | 20
> ++++++++++++++++++-
>  drivers/gpu/drm/i915/display/intel_dmc.c      | 14 ++++++++++---
>  3 files changed, 32 insertions(+), 4 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..0a1e3dc2804f 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_residency_counter;
> +		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 f45a4f9ba23c..cfa53ee84323 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"
> @@ -755,7 +756,7 @@ void gen9_sanitize_dc_state(struct intel_display
> *display)
>  void gen9_set_dc_state(struct intel_display *display, u32 state)
>  {
>  	struct i915_power_domains *power_domains = &display-
> >power.domains;
> -	u32 val;
> +	u32 val, dc5_current_count;
>  	u32 mask;
>  
>  	if (!HAS_DISPLAY(display))
> @@ -775,11 +776,28 @@ void gen9_set_dc_state(struct intel_display
> *display, u32 state)
>  		drm_err(display->drm, "DC state mismatch (0x%x ->
> 0x%x)\n",
>  			power_domains->dc_state, val & mask);
>  
> +	if (DISPLAY_VER(display) >= 14) {
> +		/* If disabling DC6, update dc6_allowed counter */
> +		if (!(state & DC_STATE_EN_UPTO_DC6) && (val &
> DC_STATE_EN_UPTO_DC6)) {
> +			dc5_current_count = intel_de_read(display,
> DG1_DMC_DEBUG_DC5_COUNT);
> +			display->power.dc6_residency_counter +=
> dc5_current_count - display->power.dc5_start_count;
> +			display->power.dc5_start_count =
> dc5_current_count;
> +		}
> +	}
> +
>  	val &= ~mask;
>  	val |= state;
>  
>  	gen9_write_dc_state(display, val);
>  
> +	if (DISPLAY_VER(display) >= 14) {
> +		/* If enabling DC6, store DC5 count */
> +		if ((state & DC_STATE_EN_UPTO_DC6)) {
> +			dc5_current_count = intel_de_read(display,
> DG1_DMC_DEBUG_DC5_COUNT);
> +			display->power.dc5_start_count =
> dc5_current_count;
> +		}
> +	}
> +
>  	power_domains->dc_state = val & mask;
>  }
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_dmc.c
> b/drivers/gpu/drm/i915/display/intel_dmc.c
> index 221d3abda791..e4d3ce796c99 100644
> --- a/drivers/gpu/drm/i915/display/intel_dmc.c
> +++ b/drivers/gpu/drm/i915/display/intel_dmc.c
> @@ -1242,6 +1242,7 @@ static int intel_dmc_debugfs_status_show(struct
> seq_file *m, void *unused)
>  	struct intel_dmc *dmc = display_to_dmc(display);
>  	intel_wakeref_t wakeref;
>  	i915_reg_t dc5_reg, dc6_reg = INVALID_MMIO_REG;
> +	u32 dc5_current_count;
>  
>  	if (!HAS_DMC(display))
>  		return -ENODEV;
> @@ -1290,9 +1291,16 @@ static int
> intel_dmc_debugfs_status_show(struct seq_file *m, void *unused)
>  	}
>  
>  	seq_printf(m, "DC3 -> DC5 count: %d\n",
> intel_de_read(display, dc5_reg));
> -	if (i915_mmio_reg_valid(dc6_reg))
> -		seq_printf(m, "DC5 -> DC6 count: %d\n",
> -			   intel_de_read(display, dc6_reg));
> +
> +	if (DISPLAY_VER(display) >= 14) {
> +		dc5_current_count = intel_de_read(display, dc5_reg);
> +		display->power.dc6_residency_counter +=
> dc5_current_count - display->power.dc5_start_count;
> +		seq_printf(m, "DC6 Residency Counter: %d\n",
> display->power.dc6_residency_counter);
> +	} else {
> +		if (i915_mmio_reg_valid(dc6_reg))
> +			seq_printf(m, "DC5 -> DC6 count: %d\n",
> +				   intel_de_read(display, dc6_reg));
> +	}
>  
>  	seq_printf(m, "program base: 0x%08x\n",
>  		   intel_de_read(display, DMC_PROGRAM(dmc-
> >dmc_info[DMC_FW_MAIN].start_mmioaddr, 0)));