[PATCH umr] Prevent reading sensors far too quickly.

[Edward O'Callaghan]

Reviewed-by: Edward O'Callaghan <funfunctor at folklore1984.net>

On 04/12/2017 11:10 PM, Tom St Denis wrote:
> On platforms without GPU_POWER sensors the thread reading sensors would proceed
> far too quickly.  So it is now rate limited to 50Hz to be consistent.
> 
> Signed-off-by: Tom St Denis <tom.stdenis at amd.com>
> ---
>  src/app/top.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/src/app/top.c b/src/app/top.c
> index 96e33ff2e1da..364180eb70f6 100644
> --- a/src/app/top.c
> +++ b/src/app/top.c
> @@ -293,18 +293,24 @@ static volatile struct umr_bitfield *sensor_bits = NULL;
>  static void *gpu_sensor_thread(void *data)
>  {
>  	struct umr_asic asic = *((struct umr_asic*)data);
> -	int size, rem, off, x;
> +	int size, rem, off, x, power;
>  	char fname[128];
> +	struct timespec ts;
> +
> +	ts.tv_sec = 0;
> +	ts.tv_nsec = 1000000000UL / 50; // limit to 50Hz
>  
>  	snprintf(fname, sizeof(fname)-1, "/sys/kernel/debug/dri/%d/amdgpu_sensors", asic.instance);
>  	asic.fd.sensors = open(fname, O_RDWR);
>  	while (!sensor_thread_quit) {
>  		rem = sizeof gpu_power_data;
>  		off = 0;
> +		power = 0;
>  		for (x = 0; sensor_bits[x].regname; ) {
>  			switch (sensor_bits[x].start) {
>  				case AMDGPU_PP_SENSOR_GPU_POWER:
>  					size = 16;
> +					power = 1;
>  					break;
>  				default:
>  					size = 4;
> @@ -316,6 +322,10 @@ static void *gpu_sensor_thread(void *data)
>  			rem -= size;
>  			x   += size / 4;
>  		}
> +
> +		// sleep for 20ms if no GPU power sensor to rate limit things a bit
> +		if (!power)
> +			nanosleep(&ts, NULL);
>  	}
>  	close(asic.fd.sensors);
>  	return NULL;
> 

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