[PATCH 4.9 54/59] ARM: omap2+: am437x: rollback to use omap3_gptimer_timer_init() - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, "Cooper Jr., Franklin" <fcooper@ti.com>,
	Grygorii Strashko <grygorii.strashko@ti.com>,
	Lokesh Vutla <lokeshvutla@ti.com>, Keerthy <j-keerthy@ti.com>,
	Tony Lindgren <tony@atomide.com>
Subject: [PATCH 4.9 54/59] ARM: omap2+: am437x: rollback to use omap3_gptimer_timer_init()
Date: Fri, 13 Jan 2017 13:02:01 +0100	[thread overview]
Message-ID: <20170113113841.428238826@linuxfoundation.org> (raw)
In-Reply-To: <20170113113839.364876751@linuxfoundation.org>

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

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

commit f86a2c875fd146d9b82c8fdd86d31084507bcf4c upstream.

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@ti.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/arch/arm/mach-omap2/board-generic.c
+++ b/arch/arm/mach-omap2/board-generic.c
@@ -306,7 +306,7 @@ DT_MACHINE_START(AM43_DT, "Generic AM43
 	.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
--- a/arch/arm/mach-omap2/timer.c
+++ b/arch/arm/mach-omap2/timer.c
@@ -510,18 +510,19 @@ void __init omap3_secure_sync32k_timer_i
 }
 #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",
