Implement gpu_busy based on the downstream msm-3.4 code [1]. This
allows us to use devfreq on this old old old hardware!

[1] 
https://github.com/LineageOS/android_kernel_sony_apq8064/blob/lineage-16.0/drivers/gpu/msm/adreno_a2xx.c#L1975

Reviewed-by: Dmitry Baryshkov <dmitry.barysh...@linaro.org>
Signed-off-by: Konrad Dybcio <konrad.dyb...@linaro.org>
---
 drivers/gpu/drm/msm/adreno/a2xx_gpu.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/gpu/drm/msm/adreno/a2xx_gpu.c 
b/drivers/gpu/drm/msm/adreno/a2xx_gpu.c
index c67089a7ebc1..104bdf28cdaf 100644
--- a/drivers/gpu/drm/msm/adreno/a2xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a2xx_gpu.c
@@ -481,6 +481,31 @@ a2xx_create_address_space(struct msm_gpu *gpu, struct 
platform_device *pdev)
        return aspace;
 }
 
+/* While the precise size of this field is unknown, it holds at least these 
three values.. */
+static u64 a2xx_gpu_busy(struct msm_gpu *gpu, unsigned long *out_sample_rate)
+{
+       u64 busy_cycles;
+
+       /* Freeze the counter */
+       gpu_write(gpu, REG_A2XX_CP_PERFMON_CNTL, PERF_STATE_FREEZE);
+
+       busy_cycles = gpu_read64(gpu, REG_A2XX_RBBM_PERFCOUNTER1_LO);
+
+       /* Reset the counter */
+       gpu_write(gpu, REG_A2XX_CP_PERFMON_CNTL, PERF_STATE_RESET);
+
+       /* Re-enable the performance monitors */
+       gpu_rmw(gpu, REG_A2XX_RBBM_PM_OVERRIDE2,
+               A2XX_RBBM_PM_OVERRIDE2_DEBUG_PERF_SCLK_PM_OVERRIDE,
+               A2XX_RBBM_PM_OVERRIDE2_DEBUG_PERF_SCLK_PM_OVERRIDE);
+       gpu_write(gpu, REG_A2XX_RBBM_PERFCOUNTER1_SELECT, 1);
+       gpu_write(gpu, REG_A2XX_CP_PERFMON_CNTL, PERF_STATE_ENABLE);
+
+       *out_sample_rate = clk_get_rate(gpu->core_clk);
+
+       return busy_cycles;
+}
+
 static u32 a2xx_get_rptr(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
 {
        ring->memptrs->rptr = gpu_read(gpu, REG_AXXX_CP_RB_RPTR);
@@ -502,6 +527,7 @@ static const struct adreno_gpu_funcs funcs = {
 #if defined(CONFIG_DEBUG_FS) || defined(CONFIG_DEV_COREDUMP)
                .show = adreno_show,
 #endif
+               .gpu_busy = a2xx_gpu_busy,
                .gpu_state_get = a2xx_gpu_state_get,
                .gpu_state_put = adreno_gpu_state_put,
                .create_address_space = a2xx_create_address_space,

-- 
2.39.2

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