linux-kernel - [PATCH v2 1/5] perf: arm_cspmu: Support 32-bit accesses to 64-bit registers

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Message-Id: <20230601030144.3458136-2-ilkka@os.amperecomputing.com>
Date:   Wed, 31 May 2023 20:01:40 -0700
From:   Ilkka Koskinen <ilkka@...amperecomputing.com>
To:     Jonathan Corbet <corbet@....net>, Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Besar Wicaksono <bwicaksono@...dia.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Robin Murphy <robin.murphy@....com>
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Ilkka Koskinen <ilkka@...amperecomputing.com>
Subject: [PATCH v2 1/5] perf: arm_cspmu: Support 32-bit accesses to 64-bit registers

Split the 64-bit register accesses if 64-bit access is not supported
by the PMU.

Signed-off-by: Ilkka Koskinen <ilkka@...amperecomputing.com>
---
 drivers/perf/arm_cspmu/arm_cspmu.c | 8 ++++++--
 drivers/perf/arm_cspmu/arm_cspmu.h | 1 +
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/perf/arm_cspmu/arm_cspmu.c b/drivers/perf/arm_cspmu/arm_cspmu.c
index a3f1c410b417..88547a2b73e6 100644
--- a/drivers/perf/arm_cspmu/arm_cspmu.c
+++ b/drivers/perf/arm_cspmu/arm_cspmu.c
@@ -701,8 +701,12 @@ static void arm_cspmu_write_counter(struct perf_event *event, u64 val)
 
 	if (use_64b_counter_reg(cspmu)) {
 		offset = counter_offset(sizeof(u64), event->hw.idx);
-
-		writeq(val, cspmu->base1 + offset);
+		if (!cspmu->impl.split_64bit_access) {
+			writeq(val, cspmu->base1 + offset);
+		} else {
+			writel(lower_32_bits(val), cspmu->base1 + offset);
+			writel(upper_32_bits(val), cspmu->base1 + offset + 4);
+		}
 	} else {
 		offset = counter_offset(sizeof(u32), event->hw.idx);
 
diff --git a/drivers/perf/arm_cspmu/arm_cspmu.h b/drivers/perf/arm_cspmu/arm_cspmu.h
index 51323b175a4a..c0412cf2bd97 100644
--- a/drivers/perf/arm_cspmu/arm_cspmu.h
+++ b/drivers/perf/arm_cspmu/arm_cspmu.h
@@ -110,6 +110,7 @@ struct arm_cspmu_impl_ops {
 /* Vendor/implementer descriptor. */
 struct arm_cspmu_impl {
 	u32 pmiidr;
+	bool split_64bit_access;
 	struct arm_cspmu_impl_ops ops;
 	void *ctx;
 };
-- 
2.40.1