drm/i915: expose command stream timestamp frequency to userspace

We use to have this fixed per generation, but starting with CNL userspace
cannot tell just off the PCI ID. Let's make this information available. This
is particularly useful for performance monitoring where much of the
normalization work is done using those timestamps (this include pipeline
statistics in both GL & Vulkan as well as OA reports).

v2: Use variables for 24MHz/19.2MHz values (Ewelina)
    Renamed function & coding style (Sagar)

v3: Fix frequency read on Broadwell (Sagar)
    Fix missing divide by 4 on <= gen4 (Sagar)
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Tested-by: Rafael Antognolli <rafael.antognolli@intel.com>
Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171110190845.32574-7-lionel.g.landwerlin@intel.com

drivers/gpu/drm/i915/i915_debugfs.c

@@ -3269,6 +3269,8 @@ static int i915_engine_info(struct seq_file *m, void *unused)
 		   yesno(dev_priv->gt.awake));
 	seq_printf(m, "Global active requests: %d\n",
 		   dev_priv->gt.active_requests);
+	seq_printf(m, "CS timestamp frequency: %llu Hz\n",
+		   dev_priv->info.cs_timestamp_frequency);
 
 	p = drm_seq_file_printer(m);
 	for_each_engine(engine, dev_priv, id)

drivers/gpu/drm/i915/i915_drv.c

@@ -419,6 +419,9 @@ static int i915_getparam(struct drm_device *dev, void *data,
 		if (!value)
 			return -ENODEV;
 		break;
+	case I915_PARAM_CS_TIMESTAMP_FREQUENCY:
+		value = INTEL_INFO(dev_priv)->cs_timestamp_frequency;
+		break;
 	default:
 		DRM_DEBUG("Unknown parameter %d\n", param->param);
 		return -EINVAL;

drivers/gpu/drm/i915/i915_drv.h

@@ -885,6 +885,8 @@ struct intel_device_info {
 	/* Slice/subslice/EU info */
 	struct sseu_dev_info sseu;
 
+	u64 cs_timestamp_frequency;
+
 	struct color_luts {
 		u16 degamma_lut_size;
 		u16 gamma_lut_size;

drivers/gpu/drm/i915/i915_reg.h

@@ -1116,9 +1116,24 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
 
 /* RPM unit config (Gen8+) */
 #define RPM_CONFIG0	    _MMIO(0x0D00)
+#define  GEN9_RPM_CONFIG0_CRYSTAL_CLOCK_FREQ_SHIFT	3
+#define  GEN9_RPM_CONFIG0_CRYSTAL_CLOCK_FREQ_MASK	(1 << GEN9_RPM_CONFIG0_CRYSTAL_CLOCK_FREQ_SHIFT)
+#define  GEN9_RPM_CONFIG0_CRYSTAL_CLOCK_FREQ_19_2_MHZ	0
+#define  GEN9_RPM_CONFIG0_CRYSTAL_CLOCK_FREQ_24_MHZ	1
+#define  GEN10_RPM_CONFIG0_CTC_SHIFT_PARAMETER_SHIFT	1
+#define  GEN10_RPM_CONFIG0_CTC_SHIFT_PARAMETER_MASK	(0x3 << GEN10_RPM_CONFIG0_CTC_SHIFT_PARAMETER_SHIFT)
+
 #define RPM_CONFIG1	    _MMIO(0x0D04)
 #define  GEN10_GT_NOA_ENABLE  (1 << 9)
 
+/* GPM unit config (Gen9+) */
+#define CTC_MODE			_MMIO(0xA26C)
+#define  CTC_SOURCE_PARAMETER_MASK 1
+#define  CTC_SOURCE_CRYSTAL_CLOCK	0
+#define  CTC_SOURCE_DIVIDE_LOGIC	1
+#define  CTC_SHIFT_PARAMETER_SHIFT	1
+#define  CTC_SHIFT_PARAMETER_MASK	(0x3 << CTC_SHIFT_PARAMETER_SHIFT)
+
 /* RCP unit config (Gen8+) */
 #define RCP_CONFIG	    _MMIO(0x0D08)
 
@@ -8863,6 +8878,12 @@ enum skl_power_gate {
 #define ILK_TIMESTAMP_HI	_MMIO(0x70070)
 #define IVB_TIMESTAMP_CTR	_MMIO(0x44070)
 
+#define GEN9_TIMESTAMP_OVERRIDE				_MMIO(0x44074)
+#define  GEN9_TIMESTAMP_OVERRIDE_US_COUNTER_DIVIDER_SHIFT	0
+#define  GEN9_TIMESTAMP_OVERRIDE_US_COUNTER_DIVIDER_MASK	0x3ff
+#define  GEN9_TIMESTAMP_OVERRIDE_US_COUNTER_DENOMINATOR_SHIFT	12
+#define  GEN9_TIMESTAMP_OVERRIDE_US_COUNTER_DENOMINATOR_MASK	(0xf << 12)
+
 #define _PIPE_FRMTMSTMP_A		0x70048
 #define PIPE_FRMTMSTMP(pipe)		\
 			_MMIO_PIPE2(pipe, _PIPE_FRMTMSTMP_A)

drivers/gpu/drm/i915/intel_device_info.c

@@ -329,6 +329,108 @@ static void broadwell_sseu_info_init(struct drm_i915_private *dev_priv)
 	sseu->has_eu_pg = 0;
 }
 
+static u64 read_reference_ts_freq(struct drm_i915_private *dev_priv)
+{
+	u32 ts_override = I915_READ(GEN9_TIMESTAMP_OVERRIDE);
+	u64 base_freq, frac_freq;
+
+	base_freq = ((ts_override & GEN9_TIMESTAMP_OVERRIDE_US_COUNTER_DIVIDER_MASK) >>
+		     GEN9_TIMESTAMP_OVERRIDE_US_COUNTER_DIVIDER_SHIFT) + 1;
+	base_freq *= 1000000;
+
+	frac_freq = ((ts_override &
+		      GEN9_TIMESTAMP_OVERRIDE_US_COUNTER_DENOMINATOR_MASK) >>
+		     GEN9_TIMESTAMP_OVERRIDE_US_COUNTER_DENOMINATOR_SHIFT);
+	if (frac_freq != 0)
+		frac_freq = 1000000 / (frac_freq + 1);
+
+	return base_freq + frac_freq;
+}
+
+static u64 read_timestamp_frequency(struct drm_i915_private *dev_priv)
+{
+	u64 f12_5_mhz = 12500000;
+	u64 f19_2_mhz = 19200000;
+	u64 f24_mhz = 24000000;
+
+	if (INTEL_GEN(dev_priv) <= 4) {
+		/* PRMs say:
+		 *
+		 *     "The value in this register increments once every 16
+		 *      hclks." (through the “Clocking Configuration”
+		 *      (“CLKCFG”) MCHBAR register)
+		 */
+		return (dev_priv->rawclk_freq * 1000) / 16;
+	} else if (INTEL_GEN(dev_priv) <= 8) {
+		/* PRMs say:
+		 *
+		 *     "The PCU TSC counts 10ns increments; this timestamp
+		 *      reflects bits 38:3 of the TSC (i.e. 80ns granularity,
+		 *      rolling over every 1.5 hours).
+		 */
+		return f12_5_mhz;
+	} else if (INTEL_GEN(dev_priv) <= 9) {
+		u32 ctc_reg = I915_READ(CTC_MODE);
+		u64 freq = 0;
+
+		if ((ctc_reg & CTC_SOURCE_PARAMETER_MASK) == CTC_SOURCE_DIVIDE_LOGIC) {
+			freq = read_reference_ts_freq(dev_priv);
+		} else {
+			freq = IS_GEN9_LP(dev_priv) ? f19_2_mhz : f24_mhz;
+
+			/* Now figure out how the command stream's timestamp
+			 * register increments from this frequency (it might
+			 * increment only every few clock cycle).
+			 */
+			freq >>= 3 - ((ctc_reg & CTC_SHIFT_PARAMETER_MASK) >>
+				      CTC_SHIFT_PARAMETER_SHIFT);
+		}
+
+		return freq;
+	} else if (INTEL_GEN(dev_priv) <= 10) {
+		u32 ctc_reg = I915_READ(CTC_MODE);
+		u64 freq = 0;
+		u32 rpm_config_reg = 0;
+
+		/* First figure out the reference frequency. There are 2 ways
+		 * we can compute the frequency, either through the
+		 * TIMESTAMP_OVERRIDE register or through RPM_CONFIG. CTC_MODE
+		 * tells us which one we should use.
+		 */
+		if ((ctc_reg & CTC_SOURCE_PARAMETER_MASK) == CTC_SOURCE_DIVIDE_LOGIC) {
+			freq = read_reference_ts_freq(dev_priv);
+		} else {
+			u32 crystal_clock;
+
+			rpm_config_reg = I915_READ(RPM_CONFIG0);
+			crystal_clock = (rpm_config_reg &
+					 GEN9_RPM_CONFIG0_CRYSTAL_CLOCK_FREQ_MASK) >>
+				GEN9_RPM_CONFIG0_CRYSTAL_CLOCK_FREQ_SHIFT;
+			switch (crystal_clock) {
+			case GEN9_RPM_CONFIG0_CRYSTAL_CLOCK_FREQ_19_2_MHZ:
+				freq = f19_2_mhz;
+				break;
+			case GEN9_RPM_CONFIG0_CRYSTAL_CLOCK_FREQ_24_MHZ:
+				freq = f24_mhz;
+				break;
+			}
+		}
+
+		/* Now figure out how the command stream's timestamp register
+		 * increments from this frequency (it might increment only
+		 * every few clock cycle).
+		 */
+		freq >>= 3 - ((rpm_config_reg &
+			       GEN10_RPM_CONFIG0_CTC_SHIFT_PARAMETER_MASK) >>
+			      GEN10_RPM_CONFIG0_CTC_SHIFT_PARAMETER_SHIFT);
+
+		return freq;
+	}
+
+	DRM_ERROR("Unknown gen, unable to compute command stream timestamp frequency\n");
+	return 0;
+}
+
 /*
  * Determine various intel_device_info fields at runtime.
  *
@@ -450,6 +552,9 @@ void intel_device_info_runtime_init(struct drm_i915_private *dev_priv)
 	else if (INTEL_GEN(dev_priv) >= 10)
 		gen10_sseu_info_init(dev_priv);
 
+	/* Initialize command stream timestamp frequency */
+	info->cs_timestamp_frequency = read_timestamp_frequency(dev_priv);
+
 	DRM_DEBUG_DRIVER("slice mask: %04x\n", info->sseu.slice_mask);
 	DRM_DEBUG_DRIVER("slice total: %u\n", hweight8(info->sseu.slice_mask));
 	DRM_DEBUG_DRIVER("subslice total: %u\n",
@@ -465,4 +570,6 @@ void intel_device_info_runtime_init(struct drm_i915_private *dev_priv)
 			 info->sseu.has_subslice_pg ? "y" : "n");
 	DRM_DEBUG_DRIVER("has EU power gating: %s\n",
 			 info->sseu.has_eu_pg ? "y" : "n");
+	DRM_DEBUG_DRIVER("CS timestamp frequency: %llu\n",
+			 info->cs_timestamp_frequency);
 }

include/uapi/drm/i915_drm.h

@@ -481,6 +481,12 @@ typedef struct drm_i915_irq_wait {
  */
 #define I915_PARAM_HAS_CONTEXT_ISOLATION 50
 
+/* Frequency of the command streamer timestamps given by the *_TIMESTAMP
+ * registers. This used to be fixed per platform but from CNL onwards, this
+ * might vary depending on the parts.
+ */
+#define I915_PARAM_CS_TIMESTAMP_FREQUENCY 51
+
 typedef struct drm_i915_getparam {
 	__s32 param;
 	/*