drm/i915: add dev.i915.oa_max_sample_rate sysctl (00319ba0) · Commits · e / devices / android_kernel_oneplus_sm8150

drivers/gpu/drm/i915/i915_perf.c

+50 −11

Original line number	Diff line number	Diff line
		@@ -82,6 +82,21 @@ static u32 i915_perf_stream_paranoid = true;
		#define INVALID_CTX_ID 0xffffffff


		/* For sysctl proc_dointvec_minmax of i915_oa_max_sample_rate
		*
		* 160ns is the smallest sampling period we can theoretically program the OA
		* unit with on Haswell, corresponding to 6.25MHz.
		*/
		static int oa_sample_rate_hard_limit = 6250000;

		/* Theoretically we can program the OA unit to sample every 160ns but don't
		* allow that by default unless root...
		*
		* The default threshold of 100000Hz is based on perf's similar
		* kernel.perf_event_max_sample_rate sysctl parameter.
		*/
		static u32 i915_oa_max_sample_rate = 100000;

		/* XXX: beware if future OA HW adds new report formats that the current
		* code assumes all reports have a power-of-two size and ~(size - 1) can
		* be used as a mask to align the OA tail pointer.
		@@ -1314,6 +1329,7 @@ static int read_properties_unlocked(struct drm_i915_private *dev_priv,
		}

		for (i = 0; i < n_props; i++) {
		u64 oa_period, oa_freq_hz;
		u64 id, value;
		int ret;

		@@ -1359,21 +1375,35 @@ static int read_properties_unlocked(struct drm_i915_private *dev_priv,
		return -EINVAL;
		}

		/* NB: The exponent represents a period as follows:
		*
		* 80ns * 2^(period_exponent + 1)
		*
		* Theoretically we can program the OA unit to sample
		/* Theoretically we can program the OA unit to sample
		* every 160ns but don't allow that by default unless
		* root.
		*
		* Referring to perf's
		* kernel.perf_event_max_sample_rate for a precedent
		* (100000 by default); with an OA exponent of 6 we get
		* a period of 10.240 microseconds -just under 100000Hz
		* On Haswell the period is derived from the exponent
		* as:
		*
		* period = 80ns * 2^(exponent + 1)
		*/
		if (value < 6 && !capable(CAP_SYS_ADMIN)) {
		DRM_ERROR("Minimum OA sampling exponent is 6 without root privileges\n");
		BUILD_BUG_ON(sizeof(oa_period) != 8);
		oa_period = 80ull * (2ull << value);

		/* This check is primarily to ensure that oa_period <=
		* UINT32_MAX (before passing to do_div which only
		* accepts a u32 denominator), but we can also skip
		* checking anything < 1Hz which implicitly can't be
		* limited via an integer oa_max_sample_rate.
		*/
		if (oa_period <= NSEC_PER_SEC) {
		u64 tmp = NSEC_PER_SEC;
		do_div(tmp, oa_period);
		oa_freq_hz = tmp;
		} else
		oa_freq_hz = 0;

		if (oa_freq_hz > i915_oa_max_sample_rate &&
		!capable(CAP_SYS_ADMIN)) {
		DRM_ERROR("OA exponent would exceed the max sampling frequency (sysctl dev.i915.oa_max_sample_rate) %uHz without root privileges\n",
		i915_oa_max_sample_rate);
		return -EACCES;
		}

		@@ -1481,6 +1511,15 @@ static struct ctl_table oa_table[] = {
		.extra1 = &zero,
		.extra2 = &one,
		},
		{
		.procname = "oa_max_sample_rate",
		.data = &i915_oa_max_sample_rate,
		.maxlen = sizeof(i915_oa_max_sample_rate),
		.mode = 0644,
		.proc_handler = proc_dointvec_minmax,
		.extra1 = &zero,
		.extra2 = &oa_sample_rate_hard_limit,
		},
		{}
		};