git: c8a4404da737 - stable/12 - hwpmc: initialize arm64 counter/interrupt state

The branch stable/12 has been updated by mhorne:

URL: https://cgit.FreeBSD.org/src/commit/?id=c8a4404da737ea7e859287094de38953a84bdd68

commit c8a4404da737ea7e859287094de38953a84bdd68
Author:     Mitchell Horne <mhorne@FreeBSD.org>
AuthorDate: 2021-11-08 19:33:25 +0000
Commit:     Mitchell Horne <mhorne@FreeBSD.org>
CommitDate: 2021-11-15 15:22:35 +0000

    hwpmc: initialize arm64 counter/interrupt state
    
    Performance counters and overflow interrupts are assumed to be disabled
    by default, but this is not guaranteed. Ensure we disable both during
    per-cpu initialization, before enabling the PMU. Otherwise, some systems
    (such as the Ampere eMAG) would experience an interrupt storm upon
    loading the hwpmc module.
    
    Reviewed by:    br
    MFC after:      5 days
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D32854
    
    (cherry picked from commit b826cc3caf6abc6a5d1926bd478b464938d45697)
---
 sys/dev/hwpmc/hwpmc_arm64.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/sys/dev/hwpmc/hwpmc_arm64.c b/sys/dev/hwpmc/hwpmc_arm64.c
index af028d3fce94..919f588afff2 100644
--- a/sys/dev/hwpmc/hwpmc_arm64.c
+++ b/sys/dev/hwpmc/hwpmc_arm64.c
@@ -454,6 +454,16 @@ arm64_pcpu_init(struct pmc_mdep *md, int cpu)
 		pc->pc_hwpmcs[i + first_ri] = phw;
 	}
 
+	/*
+	 * Disable all counters and overflow interrupts. Upon reset they are in
+	 * an undefined state.
+	 *
+	 * Don't issue an isb here, just wait for the one in arm64_pmcr_write()
+	 * to make the writes visible.
+	 */
+	WRITE_SPECIALREG(pmcntenclr_el0, 0xffffffff);
+	WRITE_SPECIALREG(pmintenclr_el1, 0xffffffff);
+
 	/* Enable unit */
 	pmcr = arm64_pmcr_read();
 	pmcr |= PMCR_E;