linux-kernel - [PATCH] arm64/sme: Don't use streaming mode to probe the maximum SME VL

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Message-Id: <20221223-arm64-sme-probe-max-v1-1-cbde68f67ad0@kernel.org>
Date:   Tue, 27 Dec 2022 13:04:35 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mark Brown <broonie@...nel.org>
Subject: [PATCH] arm64/sme: Don't use streaming mode to probe the maximum SME VL

During development the architecture added the RDSVL instruction which means
we do not need to enter streaming mode to enumerate the SME VLs, use it
when we probe the maximum supported VL. Other users were already updated.

No functional change.

Signed-off-by: Mark Brown <broonie@...nel.org>
---
 arch/arm64/kernel/fpsimd.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index dcc81e7200d4..62c67664cdaa 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1322,7 +1322,6 @@ u64 read_smcr_features(void)
 	unsigned int vq_max;
 
 	sme_kernel_enable(NULL);
-	sme_smstart_sm();
 
 	/*
 	 * Set the maximum possible VL.
@@ -1332,11 +1331,9 @@ u64 read_smcr_features(void)
 
 	smcr = read_sysreg_s(SYS_SMCR_EL1);
 	smcr &= ~(u64)SMCR_ELx_LEN_MASK; /* Only the LEN field */
-	vq_max = sve_vq_from_vl(sve_get_vl());
+	vq_max = sve_vq_from_vl(sme_get_vl());
 	smcr |= vq_max - 1; /* set LEN field to maximum effective value */
 
-	sme_smstop_sm();
-
 	return smcr;
 }
 

---
base-commit: 1b929c02afd37871d5afb9d498426f83432e71c2
change-id: 20221223-arm64-sme-probe-max-7a1378041922

Best regards,
-- 
Mark Brown <broonie@...nel.org>