Re: [PATCH v8] drm/i915/dmc: Create debugfs entry for dc6 counter

[Nautiyal, Ankit K]

On 3/21/2025 6:07 PM, 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)
v6: Change intel_dmc_get_dc6_allowed_count return type to bool. (Imre)
     Update debugfs print to better allien with old print. (Imre)
     Remove braces at if/else for signle line statements. (Imre)
v7: Remove in line variable declaration. (Imre)
v8: Rebase the changes.

Signed-off-by: Mohammed Thasleem <mohammed.thasl...@intel.com>
Reviewed-by: Imre Deak <imre.d...@intel.com>

Thanks for the patch and the reviews, patch is pushed to drm-intel-next


Regards,

Ankit

---
  .../i915/display/intel_display_power_well.c   | 11 +++-
  drivers/gpu/drm/i915/display/intel_dmc.c      | 50 ++++++++++++++++++-
  drivers/gpu/drm/i915/display/intel_dmc.h      |  1 +
  3 files changed, 60 insertions(+), 2 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 751e49b880d6..b9b4359751cc 100644
--- a/drivers/gpu/drm/i915/display/intel_display_power_well.c
+++ b/drivers/gpu/drm/i915/display/intel_display_power_well.c
@@ -749,8 +749,9 @@ 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;
@@ -769,11 +770,19 @@ 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 eb6b47ba0870..98f80a6c63e8 100644
--- a/drivers/gpu/drm/i915/display/intel_dmc.c
+++ b/drivers/gpu/drm/i915/display/intel_dmc.c
@@ -29,6 +29,7 @@
  #include "i915_reg.h"
  #include "intel_de.h"
  #include "intel_display_rpm.h"
+#include "intel_display_power_well.h"
  #include "intel_dmc.h"
  #include "intel_dmc_regs.h"
  #include "intel_step.h"
@@ -58,6 +59,10 @@ 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];
@@ -1233,6 +1238,44 @@ 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 bool intel_dmc_get_dc6_allowed_count(struct intel_display *display, u32 
*count)
+{
+       struct i915_power_domains *power_domains = &display->power.domains;
+       struct intel_dmc *dmc = display_to_dmc(display);
+       bool dc6_enabled;
+
+       if (DISPLAY_VER(display) < 14)
+               return false;
+
+       mutex_lock(&power_domains->lock);
+       dc6_enabled = intel_de_read(display, DC_STATE_EN) &
+                     DC_STATE_EN_UPTO_DC6;
+       if (dc6_enabled)
+               intel_dmc_update_dc6_allowed_count(display, false);
+
+       *count = dmc->dc6_allowed.count;
+       mutex_unlock(&power_domains->lock);
+
+       return true;
+}
+
  static int intel_dmc_debugfs_status_show(struct seq_file *m, void *unused)
  {
        struct intel_display *display = m->private;
@@ -1240,6 +1283,7 @@ static int intel_dmc_debugfs_status_show(struct seq_file 
*m, void *unused)
        struct intel_dmc *dmc = display_to_dmc(display);
        struct ref_tracker *wakeref;
        i915_reg_t dc5_reg, dc6_reg = INVALID_MMIO_REG;
+       u32 dc6_allowed_count;

if (!HAS_DMC(display))

                return -ENODEV;
@@ -1288,7 +1332,11 @@ 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))
+
+       if (intel_dmc_get_dc6_allowed_count(display, &dc6_allowed_count))
+               seq_printf(m, "DC5 -> DC6 allowed count: %d\n",
+                          dc6_allowed_count);
+       else if (i915_mmio_reg_valid(dc6_reg))
                seq_printf(m, "DC5 -> DC6 count: %d\n",
                           intel_de_read(display, dc6_reg));

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);