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Thu, 13 Dec 2018 18:01:19 +0000 Received: from rmk by rmk-PC.armlinux.org.uk with local (Exim 4.82_1-5b7a7c0-XX) (envelope-from ) id 1gXVIT-0008D2-IZ; Thu, 13 Dec 2018 18:01:17 +0000 In-Reply-To: <20181213175952.GC26090@n2100.armlinux.org.uk> References: <20181213175952.GC26090@n2100.armlinux.org.uk> From: Russell King To: linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-omap@vger.kernel.org, linux-oxnas@groups.io, linux-samsung-soc@vger.kernel.org, linux-soc@vger.kernel.org Subject: [PATCH 8/9] ARM: versatile: rename and comment SMP implementation MIME-Version: 1.0 Content-Disposition: inline Message-Id: Date: Thu, 13 Dec 2018 18:01:17 +0000 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20181213_130353_235135_01CD23DA X-CRM114-Status: GOOD ( 22.42 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Linus Walleij Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Rename pen_release and boot_lock in the Versatile specific SMP implementation, describe why these exist and state clearly that they should not be used in production implementations. Signed-off-by: Russell King --- arch/arm/plat-versatile/headsmp.S | 2 +- arch/arm/plat-versatile/hotplug.c | 4 ++- arch/arm/plat-versatile/include/plat/platsmp.h | 1 + arch/arm/plat-versatile/platsmp.c | 47 ++++++++++++++++++-------- 4 files changed, 38 insertions(+), 16 deletions(-) diff --git a/arch/arm/plat-versatile/headsmp.S b/arch/arm/plat-versatile/headsmp.S index 40f27e52de75..e99396dfa6f3 100644 --- a/arch/arm/plat-versatile/headsmp.S +++ b/arch/arm/plat-versatile/headsmp.S @@ -37,5 +37,5 @@ pen: ldr r7, [r6] .align 1: .long . - .long pen_release + .long versatile_cpu_release ENDPROC(versatile_secondary_startup) diff --git a/arch/arm/plat-versatile/hotplug.c b/arch/arm/plat-versatile/hotplug.c index e2d3e9035d0f..c974958417fe 100644 --- a/arch/arm/plat-versatile/hotplug.c +++ b/arch/arm/plat-versatile/hotplug.c @@ -18,6 +18,8 @@ #include #include +#include + static inline void versatile_immitation_enter_lowpower(unsigned int actrl_mask) { unsigned int v; @@ -67,7 +69,7 @@ static inline void versatile_immitation_do_lowpower(unsigned int cpu, int *spuri for (;;) { wfi(); - if (pen_release == cpu_logical_map(cpu)) { + if (versatile_cpu_release == cpu_logical_map(cpu)) { /* * OK, proper wakeup, we're done */ diff --git a/arch/arm/plat-versatile/include/plat/platsmp.h b/arch/arm/plat-versatile/include/plat/platsmp.h index 9fff1f241c9e..1b087fbbc700 100644 --- a/arch/arm/plat-versatile/include/plat/platsmp.h +++ b/arch/arm/plat-versatile/include/plat/platsmp.h @@ -8,6 +8,7 @@ * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ +extern volatile int versatile_cpu_release; extern void versatile_secondary_startup(void); extern void versatile_secondary_init(unsigned int cpu); diff --git a/arch/arm/plat-versatile/platsmp.c b/arch/arm/plat-versatile/platsmp.c index 6b60f582b738..6e2836243187 100644 --- a/arch/arm/plat-versatile/platsmp.c +++ b/arch/arm/plat-versatile/platsmp.c @@ -7,6 +7,11 @@ * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. + * + * This code is specific to the hardware found on ARM Realview and + * Versatile Express platforms where the CPUs are unable to be individually + * woken, and where there is no way to hot-unplug CPUs. Real platforms + * should not copy this code. */ #include #include @@ -21,18 +26,32 @@ #include /* - * Write pen_release in a way that is guaranteed to be visible to all - * observers, irrespective of whether they're taking part in coherency + * versatile_cpu_release controls the release of CPUs from the holding + * pen in headsmp.S, which exists because we are not always able to + * control the release of individual CPUs from the board firmware. + * Production platforms do not need this. + */ +volatile int versatile_cpu_release = -1; + +/* + * Write versatile_cpu_release in a way that is guaranteed to be visible to + * all observers, irrespective of whether they're taking part in coherency * or not. This is necessary for the hotplug code to work reliably. */ -static void write_pen_release(int val) +static void versatile_write_cpu_release(int val) { - pen_release = val; + versatile_cpu_release = val; smp_wmb(); - sync_cache_w(&pen_release); + sync_cache_w(&versatile_cpu_release); } -static DEFINE_RAW_SPINLOCK(boot_lock); +/* + * versatile_lock exists to avoid running the loops_per_jiffy delay loop + * calibrations on the secondary CPU while the requesting CPU is using + * the limited-bandwidth bus - which affects the calibration value. + * Production platforms do not need this. + */ +static DEFINE_RAW_SPINLOCK(versatile_lock); void versatile_secondary_init(unsigned int cpu) { @@ -40,13 +59,13 @@ void versatile_secondary_init(unsigned int cpu) * let the primary processor know we're out of the * pen, then head off into the C entry point */ - write_pen_release(-1); + versatile_write_cpu_release(-1); /* * Synchronise with the boot thread. */ - raw_spin_lock(&boot_lock); - raw_spin_unlock(&boot_lock); + raw_spin_lock(&versatile_lock); + raw_spin_unlock(&versatile_lock); } int versatile_boot_secondary(unsigned int cpu, struct task_struct *idle) @@ -57,7 +76,7 @@ int versatile_boot_secondary(unsigned int cpu, struct task_struct *idle) * Set synchronisation state between this boot processor * and the secondary one */ - raw_spin_lock(&boot_lock); + raw_spin_lock(&versatile_lock); /* * This is really belt and braces; we hold unintended secondary @@ -65,7 +84,7 @@ int versatile_boot_secondary(unsigned int cpu, struct task_struct *idle) * since we haven't sent them a soft interrupt, they shouldn't * be there. */ - write_pen_release(cpu_logical_map(cpu)); + versatile_write_cpu_release(cpu_logical_map(cpu)); /* * Send the secondary CPU a soft interrupt, thereby causing @@ -77,7 +96,7 @@ int versatile_boot_secondary(unsigned int cpu, struct task_struct *idle) timeout = jiffies + (1 * HZ); while (time_before(jiffies, timeout)) { smp_rmb(); - if (pen_release == -1) + if (versatile_cpu_release == -1) break; udelay(10); @@ -87,7 +106,7 @@ int versatile_boot_secondary(unsigned int cpu, struct task_struct *idle) * now the secondary core is starting up let it run its * calibrations, then wait for it to finish */ - raw_spin_unlock(&boot_lock); + raw_spin_unlock(&versatile_lock); - return pen_release != -1 ? -ENOSYS : 0; + return versatile_cpu_release != -1 ? -ENOSYS : 0; }