Re: [PATCH v5] drm/i915/dmc: Create debugfs entry for dc6 counter

[Imre Deak <imre.deak@intel.com>]

On Wed, Mar 12, 2025 at 08:13:10PM +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)
> v4: Remove superfluous whitespace. (Jani)
>     Read DMC registers in intel_dmc.c (Jani)
>     Rename dc6_en_dis to dc6_enabled and change its type to bool. (Jani)
>     Rename update_dc6_count and move it to intel_dmc.c (Jani)
>     Rename dc6_en_dis to start_tracking. (Imre)
>     Have lock for dc6 state read aswelll. (Imre)
>     Keep the existing way print 'DC5 -> DC6 count' along with
>     new 'DC6 Allowed Count' print. (Imre)
>     Add counters in intel_dmc struct. (Imre)
>     Have interface to return dc6 allowed count. (Imre)
>     Rename dc6_count to dc6_allowed_count. (Rodrigo)
> v5: Rename counters and move in to dc6_allowed structure. (Imre)
>     Order declaration lines in decreasing line length. (Imre)
>     Update start_tacking logic. (Imre)
>     Move get couner inside lock and DISPLAY_VER code to helper. (Imre)
> 
> Signed-off-by: Mohammed Thasleem <mohammed.thasleem@intel.com>
> ---
>  .../i915/display/intel_display_power_well.c   | 11 +++-
>  drivers/gpu/drm/i915/display/intel_dmc.c      | 54 +++++++++++++++++--
>  drivers/gpu/drm/i915/display/intel_dmc.h      |  1 +
>  3 files changed, 62 insertions(+), 4 deletions(-)
> 
> 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 8ec87ffd87d2..574352439573 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_power_well.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_power_well.c
> @@ -752,8 +752,9 @@ 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;
> +	bool dc6_was_enabled, enable_dc6;
>  	u32 mask;
> +	u32 val;
>  
>  	if (!HAS_DISPLAY(display))
>  		return;
> @@ -772,11 +773,19 @@ 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);
>  
> +	enable_dc6 = state & DC_STATE_EN_UPTO_DC6;
> +	dc6_was_enabled = val & DC_STATE_EN_UPTO_DC6;
> +	if (!dc6_was_enabled && enable_dc6)
> +		intel_dmc_update_dc6_allowed_count(display, true);
> +
>  	val &= ~mask;
>  	val |= state;
>  
>  	gen9_write_dc_state(display, val);
>  
> +	if (!enable_dc6 && dc6_was_enabled)
> +		intel_dmc_update_dc6_allowed_count(display, false);
> +
>  	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 fa6944e55d95..95abeec0586a 100644
> --- a/drivers/gpu/drm/i915/display/intel_dmc.c
> +++ b/drivers/gpu/drm/i915/display/intel_dmc.c
> @@ -28,6 +28,7 @@
>  #include "i915_drv.h"
>  #include "i915_reg.h"
>  #include "intel_de.h"
> +#include "intel_display_power_well.h"
>  #include "intel_dmc.h"
>  #include "intel_dmc_regs.h"
>  #include "intel_step.h"
> @@ -57,6 +58,10 @@ struct intel_dmc {
>  	const char *fw_path;
>  	u32 max_fw_size; /* bytes */
>  	u32 version;
> +	struct {
> +		u32 dc5_start;
> +		u32 count;
> +	} dc6_allowed;
>  	struct dmc_fw_info {
>  		u32 mmio_count;
>  		i915_reg_t mmioaddr[20];
> @@ -1232,6 +1237,43 @@ void intel_dmc_snapshot_print(const struct intel_dmc_snapshot *snapshot, struct
>  			   DMC_VERSION_MINOR(snapshot->version));
>  }
>  
> +void intel_dmc_update_dc6_allowed_count(struct intel_display *display,
> +					bool start_tracking)
> +{
> +	struct intel_dmc *dmc = display_to_dmc(display);
> +	u32 dc5_cur_count;
> +
> +	if (DISPLAY_VER(dmc->display) < 14)
> +		return;
> +
> +	dc5_cur_count = intel_de_read(dmc->display, DG1_DMC_DEBUG_DC5_COUNT);
> +
> +	if (!start_tracking)
> +		dmc->dc6_allowed.count += dc5_cur_count - dmc->dc6_allowed.dc5_start;
> +
> +	dmc->dc6_allowed.dc5_start = dc5_cur_count;
> +}
> +
> +static u32 intel_dmc_get_dc6_allowed_count(struct intel_display *display, u32 *count)

The return type isn't compatible with the -ENODEV returned value. I'd
just return a bool, since the reason for an error is always the same.

> +{
> +	struct i915_power_domains *power_domains = &display->power.domains;
> +	struct intel_dmc *dmc = display_to_dmc(display);
> +
> +	if (DISPLAY_VER(display) < 14)
> +		return -ENODEV;
> +
> +	mutex_lock(&power_domains->lock);
> +	bool dc6_enabled = DC_STATE_EN_UPTO_DC6 &
> +			   intel_de_read(display, DC_STATE_EN);
> +	if (dc6_enabled)
> +		intel_dmc_update_dc6_allowed_count(display, false);
> +
> +	*count = dmc->dc6_allowed.count;
> +	mutex_unlock(&power_domains->lock);
> +
> +	return 0;
> +}
> +
>  static int intel_dmc_debugfs_status_show(struct seq_file *m, void *unused)
>  {
>  	struct intel_display *display = m->private;
> @@ -1239,6 +1281,7 @@ 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 dc6_allowed_count;
>  
>  	if (!HAS_DMC(display))
>  		return -ENODEV;
> @@ -1287,9 +1330,14 @@ 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 (intel_dmc_get_dc6_allowed_count(display, &dc6_allowed_count) == 0) {
> +		seq_printf(m, "DC6 Allowed Count : %d\n", dc6_allowed_count);

"DC5 -> DC6 allowed count: %d\n" would align better with the other
entries printed.

> +	} else {
> +		if (i915_mmio_reg_valid(dc6_reg)) {

The above else/if could be combined to 'else if (i915_mmio_reg_valid(...))'
and the {} could be dropped from around both resultant if branches.

With the above fixed the patch looks ok to me:

Reviewed-by: Imre Deak <imre.deak@intel.com>

> +			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)));
> diff --git a/drivers/gpu/drm/i915/display/intel_dmc.h b/drivers/gpu/drm/i915/display/intel_dmc.h
> index 44cecef98e73..c78426eb4cd5 100644
> --- a/drivers/gpu/drm/i915/display/intel_dmc.h
> +++ b/drivers/gpu/drm/i915/display/intel_dmc.h
> @@ -26,6 +26,7 @@ void intel_dmc_debugfs_register(struct intel_display *display);
>  
>  struct intel_dmc_snapshot *intel_dmc_snapshot_capture(struct intel_display *display);
>  void intel_dmc_snapshot_print(const struct intel_dmc_snapshot *snapshot, struct drm_printer *p);
> +void intel_dmc_update_dc6_allowed_count(struct intel_display *display, bool start_tracking);
>  
>  void assert_dmc_loaded(struct intel_display *display);
>  
> -- 
> 2.43.0
>