linux-kernel - [PATCH] Revert "powerpc/powernv/idle: Replace CPU feature check with PVR check"

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Date:   Wed, 26 Aug 2020 13:59:18 +0530
From:   Pratik Rajesh Sampat <psampat@...ux.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org, mpe@...erman.id.au,
        npiggin@...il.com, mikey@...ling.org, ego@...ux.vnet.ibm.com,
        svaidy@...ux.ibm.com, linux-kernel@...r.kernel.org,
        pratik.r.sampat@...il.com, psampat@...ux.ibm.com
Subject: [PATCH] Revert "powerpc/powernv/idle: Replace CPU feature check with PVR check"

Cpuidle stop state implementation has minor optimizations for P10
where hardware preserves more SPR registers compared to P9.
The current P9 driver works for P10, although does few extra
save-restores. P9 driver can provide the required power management
features like SMT thread folding and core level power savings
on a P10 platform.

Until the P10 stop driver is available, revert the commit which
allows for only P9 systems to utilize cpuidle and blocks all
idle stop states for P10.
Cpu idle states are enabled and tested on the P10 platform
with this fix.

This reverts commit 8747bf36f312356f8a295a0c39ff092d65ce75ae.

Fixes: 8747bf36f312 ("powerpc/powernv/idle: Replace CPU feature check with PVR check")
Signed-off-by: Pratik Rajesh Sampat <psampat@...ux.ibm.com>
---
 @mpe: This revert would resolve a staging issue wherein the P10 stop
 driver is not yet ready while cpuidle stop states need not be blocked
 on 5.9 for Power10 systems which could cause SMT folding related
 performance issues.

 The P10 stop driver is in the works here:
 https://lists.ozlabs.org/pipermail/linuxppc-dev/2020-August/216773.html

 arch/powerpc/platforms/powernv/idle.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
index 77513a80cef9..345ab062b21a 100644
--- a/arch/powerpc/platforms/powernv/idle.c
+++ b/arch/powerpc/platforms/powernv/idle.c
@@ -1223,7 +1223,7 @@ static void __init pnv_probe_idle_states(void)
 		return;
 	}
 
-	if (pvr_version_is(PVR_POWER9))
+	if (cpu_has_feature(CPU_FTR_ARCH_300))
 		pnv_power9_idle_init();
 
 	for (i = 0; i < nr_pnv_idle_states; i++)
-- 
2.25.4