platform: tegra: introduce bwmgr kernel driver

This driver exposes EMC frequency control interface to user space via
linux devfreq framework.

Users could change EMC frequency to the frequency value from the
available frequencies of EMC clock:

$ /sys/class/devfreq/bwmgr# cat available_frequencies
665600000 2750000000 3200000000 4266000000

and update the EMC floor frequency by writing into the min_freq QoS
sysfs node:

$ /sys/class/devfreq/bwmgr# echo 4266000000 > min_freq

and update the EMC max frequency by writing into the max_rate QoS
sysfs node to cap the EMC frequency:

$ /sys/class/devfreq/bwmgr# echo 4266000000 > max_freq

This driver does not directly manage the EMC clock rate. Instead it
just delivers the min/max frequency information to BPMP, and BPMP is
still the only entity that has the full control of EMC and other
related memory clocks.

Bug 5483386
Bug 5196455

Change-Id: I6124eeb7411a13bde5c51582064534063abca8d3
Signed-off-by: Johnny Liu <johnliu@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/3453755
GVS: buildbot_gerritrpt <buildbot_gerritrpt@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Reviewed-by: Rajkumar Kasirajan <rkasirajan@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

scripts/conftest/conftest.sh

@@ -8699,6 +8699,19 @@ compile_test() {
             }"
 
             compile_check_conftest "$CODE" "NV_TEGRA_IVC_USE_IVC_EXT_DRIVER" "" "types"
+	;;
+
+        tegra264_bwmgr_debug_macro)
+            #
+            # Determine if the 'TEGRA264_BWMGR_DEBUG' macro present or not
+            #
+            CODE="
+            #include <linux/tegra264-bwmgr.h>
+            int conftest_tegra264_bwmgr_debug_macro() {
+                    return TEGRA264_BWMGR_DEBUG;
+            }"
+
+            compile_check_conftest "$CODE" "NV_TEGRA264_BWMGR_DEBUG_MACRO_PRESENT" "" "macros"
         ;;
 
         thermal_zone_device_priv)