temp_metrics: Set GPU min freq

On systems with modems, a harmonic of the lowest GPU frequency
of 350Mhz interferes with the cellular signal.  Set the minimum
GPU frequency for such systems to 450Mhz.

BUG=chrome-os-partner:16439
TEST="cat /sys/kernel/debug/dri/0/i915_min_freq". On systems without
this modem, it should read back 350.  On systems with the modem, it
should read back 450.
BRANCH=none

Change-Id: I103a55af11955aed2f3e8c945904444475c63865
Signed-off-by: Sameer Nanda <snanda@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/38826
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-by: Todd Broch <tbroch@chromium.org>

util/temp_metrics.conf

@@ -142,9 +142,21 @@ script
     done
   }
 
-  set_gpu_freq() {
-    gpu_freq=$1
-    echo $gpu_freq > /sys/kernel/debug/dri/0/i915_max_freq
+  set_gpu_min_freq() {
+    GPU_MIN_FREQ=350
+    if lsusb -d 1410:9010; then
+      # Set min GPU freq to 450 to reduce intereference with modem.
+      GPU_MIN_FREQ=450
+    fi
+    echo $GPU_MIN_FREQ > /sys/kernel/debug/dri/0/i915_min_freq
+  }
+
+  set_gpu_max_freq() {
+    gpu_max_freq=$1
+    if [ $GPU_MIN_FREQ -gt $gpu_max_freq ]; then
+      gpu_max_freq=$GPU_MIN_FREQ
+    fi
+    echo $gpu_max_freq > /sys/kernel/debug/dri/0/i915_max_freq
   }
 
   set_duty_cycle() {
@@ -240,7 +252,7 @@ script
     pkg_power_limit=$(get_field $PKG_POWER_LIMIT_FIELD "$step")
 
     set_cpu_freq $cpu_max_freq $cpu_min_freq
-    set_gpu_freq $gpu_max_freq
+    set_gpu_max_freq $gpu_max_freq
     set_duty_cycle $cpu_duty_cycle
     set_pkg_power_limit $pkg_power_limit
   }
@@ -332,6 +344,9 @@ script
   # Set sensor calibration data.
   set_calibration_data
 
+  # Set minimum GPU frequency.
+  set_gpu_min_freq
+
   loop_count=0
   ec_fan_loop=0