linux-kernel - [PATCH v3 04/11] irqchip: mips-gic: Support multi-cluster in for_each_online_cpu

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Message-Id: <20231031164927.371663-5-aleksandar.rikalo@syrmia.com>
Date:   Tue, 31 Oct 2023 17:49:20 +0100
From:   Aleksandar Rikalo <aleksandar.rikalo@...mia.com>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     Aleksandar Rikalo <arikalo@...il.com>,
        Chao-ying Fu <cfu@...ecomp.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Dragan Mladjenovic <dragan.mladjenovic@...mia.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Ungerer <gerg@...nel.org>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Ilya Lipnitskiy <ilya.lipnitskiy@...il.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
        Marc Zyngier <maz@...nel.org>,
        Paul Burton <paulburton@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Serge Semin <fancer.lancer@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>
Subject: [PATCH v3 04/11] irqchip: mips-gic: Support multi-cluster in for_each_online_cpu_gic()

From: Paul Burton <paulburton@...nel.org>

Introduce support for multi-cluster GIC register access in
__gic_with_next_online_cpu(), and therefore in its user
for_each_online_cpu_gic(). We access registers in remote clusters
using the CM's GCR_CL_REDIRECT register, and so here we delegate
to mips_cm_lock_other() in order to configure this access.

With this done, users of gic_with_each_online_cpu() gain support
for multi-cluster with no further changes.

Signed-off-by: Paul Burton <paulburton@...nel.org>
Signed-off-by: Chao-ying Fu <cfu@...ecomp.com>
Signed-off-by: Dragan Mladjenovic <dragan.mladjenovic@...mia.com>
Signed-off-by: Aleksandar Rikalo <aleksandar.rikalo@...mia.com>
---
 drivers/irqchip/irq-mips-gic.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-mips-gic.c b/drivers/irqchip/irq-mips-gic.c
index 9e7182150b5c..317ccc2593d1 100644
--- a/drivers/irqchip/irq-mips-gic.c
+++ b/drivers/irqchip/irq-mips-gic.c
@@ -70,6 +70,20 @@ static int __gic_with_next_online_cpu(int prev)
 {
 	unsigned int cpu;
 
+	/*
+	 * Unlock access to the previous CPU's GIC local register block.
+	 *
+	 * Delegate to the CM locking code in the multi-cluster case, since
+	 * other clusters can only be accessed using GCR_CL_REDIRECT.
+	 *
+	 * In the single cluster case we don't need to do anything; the caller
+	 * is responsible for maintaining gic_lock & nothing should be
+	 * expecting any particular value of GIC_VL_OTHER so we can leave it
+	 * as-is.
+	 */
+	if ((prev != -1) && mips_cps_multicluster_cpus())
+		mips_cm_unlock_other();
+
 	/* Discover the next online CPU */
 	cpu = cpumask_next(prev, cpu_online_mask);
 
@@ -80,10 +94,16 @@ static int __gic_with_next_online_cpu(int prev)
 	/*
 	 * Lock access to the next CPU's GIC local register block.
 	 *
+	 * Delegate to the CM locking code in the multi-cluster case, since
+	 * other clusters can only be accessed using GCR_CL_REDIRECT.
+	 *
 	 * In the single cluster case we simply set GIC_VL_OTHER. The caller
 	 * holds gic_lock so nothing can clobber the value we write.
 	 */
-	write_gic_vl_other(mips_cm_vp_id(cpu));
+	if (mips_cps_multicluster_cpus())
+		mips_cm_lock_other_cpu(cpu, CM_GCR_Cx_OTHER_BLOCK_LOCAL);
+	else
+		write_gic_vl_other(mips_cm_vp_id(cpu));
 
 	return cpu;
 }
@@ -105,6 +125,9 @@ static inline void __lockdep_assert_held(raw_spinlock_t *gic_lock)
  *
  * The caller must hold gic_lock throughout the loop, such that GIC_VL_OTHER
  * cannot be clobbered.
+ *
+ * Please note that if you start a loop this way, it must be completed to the
+ * end, otherwise, GIC local register block will remain locked.
  */
 #define for_each_online_cpu_gic(cpu, gic_lock)		\
 	for (__lockdep_assert_held(gic_lock),		\
-- 
2.25.1