linux-kernel - [PATCH v2] ARM: omap2: am437x: rollback to use omap3_gptimer_timer

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Date:   Mon, 5 Dec 2016 09:27:44 +0530
From:   Keerthy <j-keerthy@...com>
To:     <tony@...mide.com>
CC:     <j-keerthy@...com>, <t-kristo@...com>, <linux@...linux.org.uk>,
        <linux-omap@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Lokesh Vutla <lokeshvutla@...com>
Subject: [PATCH v2] ARM: omap2: am437x: rollback to use omap3_gptimer_timer_init()

From: Grygorii Strashko <grygorii.strashko@...com>

The commit 55ee7017ee31 ("arm: omap2: board-generic: use
omap4_local_timer_init for AM437x") unintentionally changes the
clocksource devices for AM437x from OMAP GP Timer to SyncTimer32K.

Unfortunately, the SyncTimer32K is starving from frequency deviation
as mentioned in commit 5b5c01359152 ("ARM: OMAP2+: AM43x: Use gptimer
as clocksource") and, as reported by Franklin [1], even its monotonic
nature is under question (most probably there is a HW issue, but it's
still under investigation).

Taking into account above facts It's reasonable to rollback to the use
of omap3_gptimer_timer_init().

[1] http://www.spinics.net/lists/linux-omap/msg127425.html

Fixes: 55ee7017ee31 ("arm: omap2: board-generic: use
omap4_local_timer_init for AM437x")
Reported-by: Cooper Jr., Franklin <fcooper@...com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
Signed-off-by: Lokesh Vutla <lokeshvutla@...com>
Signed-off-by: Keerthy <j-keerthy@...com>
---

Changes in v2:

  * Added a proper Fixes tag with the commit ID.

 arch/arm/mach-omap2/board-generic.c | 2 +-
 arch/arm/mach-omap2/timer.c         | 9 +++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/arm/mach-omap2/board-generic.c b/arch/arm/mach-omap2/board-generic.c
index 36d9943..dc9e34e 100644
--- a/arch/arm/mach-omap2/board-generic.c
+++ b/arch/arm/mach-omap2/board-generic.c
@@ -304,7 +304,7 @@ static void __init rx51_reserve(void)
 	.init_late	= am43xx_init_late,
 	.init_irq	= omap_gic_of_init,
 	.init_machine	= omap_generic_init,
-	.init_time	= omap4_local_timer_init,
+	.init_time	= omap3_gptimer_timer_init,
 	.dt_compat	= am43_boards_compat,
 	.restart	= omap44xx_restart,
 MACHINE_END
diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c
index 5e2e221..b2f2448 100644
--- a/arch/arm/mach-omap2/timer.c
+++ b/arch/arm/mach-omap2/timer.c
@@ -510,18 +510,19 @@ void __init omap3_secure_sync32k_timer_init(void)
 }
 #endif /* CONFIG_ARCH_OMAP3 */
 
-#if defined(CONFIG_ARCH_OMAP3) || defined(CONFIG_SOC_AM33XX)
+#if defined(CONFIG_ARCH_OMAP3) || defined(CONFIG_SOC_AM33XX) || \
+	defined(CONFIG_SOC_AM43XX)
 void __init omap3_gptimer_timer_init(void)
 {
 	__omap_sync32k_timer_init(2, "timer_sys_ck", NULL,
 			1, "timer_sys_ck", "ti,timer-alwon", true);
-
-	clocksource_probe();
+	if (of_have_populated_dt())
+		clocksource_probe();
 }
 #endif
 
 #if defined(CONFIG_ARCH_OMAP4) || defined(CONFIG_SOC_OMAP5) ||		\
-	defined(CONFIG_SOC_DRA7XX) || defined(CONFIG_SOC_AM43XX)
+	defined(CONFIG_SOC_DRA7XX)
 static void __init omap4_sync32k_timer_init(void)
 {
 	__omap_sync32k_timer_init(1, "timer_32k_ck", "ti,timer-alwon",
-- 
1.9.1