sbi: sbi_pmu: Add hw_counter_filter_mode() to pmu device

Add support for custom PMU extensions to set inhibit bits
on custom CSRs by introducing the PMU device callback
hw_counter_filter_mode(). This allows the perf tool to
restrict event counting under a specified privileged
mode by appending a modifier, e.g. perf record -e event:k
to count events only happening in kernel mode.

Signed-off-by: Yu Chien Peter Lin <peterlin@andestech.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

include/sbi/sbi_pmu.h

@@ -89,6 +89,12 @@ struct sbi_pmu_device {
 	 * Custom function returning the machine-specific irq-bit.
 	 */
 	int (*hw_counter_irq_bit)(void);
+
+	/**
+	 * Custom function to inhibit counting of events while in
+	 * specified mode.
+	 */
+	void (*hw_counter_filter_mode)(unsigned long flags, int counter_index);
 };
 
 /** Get the PMU platform device */