tools/power/turbostat: Support alternative graphics sysfs knobs

/sys/class/graphics/fb0/device/drm/card0/ and /sys/class/drm/card0/
point to the same device node.
But in some cases, one exists and the other one does not.

Prefer to use /sys/class/drm/card0/, and fall back to
/sys/class/graphics/fb0/device/drm/card0/.

This recovers the "GFXMHz" and "GFXAMHz" columns on some platforms like
a SPR server.
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Reviewed-by: Len Brown <len.brown@intel.com>

tools/power/x86/turbostat/turbostat.c

@@ -3188,8 +3188,8 @@ int snapshot_gfx_rc6_ms(void)
 /*
  * snapshot_gfx_mhz()
  *
- * record snapshot of
- * /sys/class/graphics/fb0/device/drm/card0/gt_cur_freq_mhz
+ * fall back to /sys/class/graphics/fb0/device/drm/card0/gt_cur_freq_mhz
+ * when /sys/class/drm/card0/gt_cur_freq_mhz is not available.
  *
  * return 1 if config change requires a restart, else return 0
  */
@@ -3198,9 +3198,11 @@ int snapshot_gfx_mhz(void)
 	static FILE *fp;
 	int retval;
 
-	if (fp == NULL)
-		fp = fopen_or_die("/sys/class/graphics/fb0/device/drm/card0/gt_cur_freq_mhz", "r");
-	else {
+	if (fp == NULL) {
+		fp = fopen("/sys/class/drm/card0/gt_cur_freq_mhz", "r");
+		if (!fp)
+			fp = fopen_or_die("/sys/class/graphics/fb0/device/drm/card0/gt_cur_freq_mhz", "r");
+	} else {
 		rewind(fp);
 		fflush(fp);
 	}
@@ -3215,8 +3217,8 @@ int snapshot_gfx_mhz(void)
 /*
  * snapshot_gfx_cur_mhz()
  *
- * record snapshot of
- * /sys/class/graphics/fb0/device/drm/card0/gt_act_freq_mhz
+ * fall back to /sys/class/graphics/fb0/device/drm/card0/gt_act_freq_mhz
+ * when /sys/class/drm/card0/gt_act_freq_mhz is not available.
  *
  * return 1 if config change requires a restart, else return 0
  */
@@ -3225,9 +3227,11 @@ int snapshot_gfx_act_mhz(void)
 	static FILE *fp;
 	int retval;
 
-	if (fp == NULL)
-		fp = fopen_or_die("/sys/class/graphics/fb0/device/drm/card0/gt_act_freq_mhz", "r");
-	else {
+	if (fp == NULL) {
+		fp = fopen("/sys/class/drm/card0/gt_act_freq_mhz", "r");
+		if (!fp)
+			fp = fopen_or_die("/sys/class/graphics/fb0/device/drm/card0/gt_act_freq_mhz", "r");
+	} else {
 		rewind(fp);
 		fflush(fp);
 	}
@@ -5804,10 +5808,12 @@ void process_cpuid()
 	if (!access("/sys/class/drm/card0/power/rc6_residency_ms", R_OK))
 		BIC_PRESENT(BIC_GFX_rc6);
 
-	if (!access("/sys/class/graphics/fb0/device/drm/card0/gt_cur_freq_mhz", R_OK))
+	if (!access("/sys/class/drm/card0/gt_cur_freq_mhz", R_OK) ||
+	    !access("/sys/class/graphics/fb0/device/drm/card0/gt_cur_freq_mhz", R_OK))
 		BIC_PRESENT(BIC_GFXMHz);
 
-	if (!access("/sys/class/graphics/fb0/device/drm/card0/gt_act_freq_mhz", R_OK))
+	if (!access("/sys/class/drm/card0/gt_act_freq_mhz", R_OK) ||
+	    !access("/sys/class/graphics/fb0/device/drm/card0/gt_act_freq_mhz", R_OK))
 		BIC_PRESENT(BIC_GFXACTMHz);
 
 	if (!access("/sys/devices/system/cpu/cpuidle/low_power_idle_cpu_residency_us", R_OK))