drm/msm/a4xx: Implement .gpu_busy

Add support for gpu_busy on a4xx, which is required for devfreq
support.
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/523791/
Link: https://lore.kernel.org/r/20230223-topic-opp-v3-6-5f22163cd1df@linaro.orgSigned-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/adreno/a4xx_gpu.c

@@ -611,6 +611,16 @@ static int a4xx_get_timestamp(struct msm_gpu *gpu, uint64_t *value)
 	return 0;
 }
 
+static u64 a4xx_gpu_busy(struct msm_gpu *gpu, unsigned long *out_sample_rate)
+{
+	u64 busy_cycles;
+
+	busy_cycles = gpu_read64(gpu, REG_A4XX_RBBM_PERFCTR_RBBM_1_LO);
+	*out_sample_rate = clk_get_rate(gpu->core_clk);
+
+	return busy_cycles;
+}
+
 static u32 a4xx_get_rptr(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
 {
 	ring->memptrs->rptr = gpu_read(gpu, REG_A4XX_CP_RB_RPTR);
@@ -632,6 +642,7 @@ static const struct adreno_gpu_funcs funcs = {
 #if defined(CONFIG_DEBUG_FS) || defined(CONFIG_DEV_COREDUMP)
 		.show = adreno_show,
 #endif
+		.gpu_busy = a4xx_gpu_busy,
 		.gpu_state_get = a4xx_gpu_state_get,
 		.gpu_state_put = adreno_gpu_state_put,
 		.create_address_space = adreno_create_address_space,