linux-kernel - [PATCH B 08/10] OMAP: wait for pwrdm transition after clk

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Message-ID: <20090128024428.27240.35785.stgit@localhost.localdomain>
Date:	Tue, 27 Jan 2009 19:44:31 -0700
From:	Paul Walmsley <paul@...an.com>
To:	linux-arm-kernel@...ts.arm.linux.org.uk,
	linux-kernel@...r.kernel.org
Cc:	linux-omap@...r.kernel.org,
	Tomi Valkeinen <tomi.valkeinen@...ia.com>,
	Paul Walmsley <paul@...an.com>,
	Tony Lindgren <tony@...mide.com>
Subject: [PATCH B 08/10] OMAP: wait for pwrdm transition after clk_enable()

From: Tomi Valkeinen <tomi.valkeinen@...ia.com>

Enabling clock in a disabled power domain causes the power domain to be
turned on. However, the power transition is not always finished when
clk_enable() returns and this randomly crashes the kernel when an
interrupt happens right after the clk_enable, and the kernel tries to
read the irq status register for that domain.

Why the irq status register is inaccessible, I don't know. Also it
doesn't seem to be related to the module being not powered up, but to
the transition itself.

The same could perhaps happen after clk_disable also, but I have not
witnessed that.

The problem affects at least dss, cam and sgx clocks.

This change waits for the transition to be finished before returning
from omap2_clkdm_clk_enable().

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...ia.com>
Signed-off-by: Paul Walmsley <paul@...an.com>
Signed-off-by: Tony Lindgren <tony@...mide.com>
---
 arch/arm/mach-omap2/clockdomain.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/arch/arm/mach-omap2/clockdomain.c b/arch/arm/mach-omap2/clockdomain.c
index 882809d..ad6dfe4 100644
--- a/arch/arm/mach-omap2/clockdomain.c
+++ b/arch/arm/mach-omap2/clockdomain.c
@@ -561,6 +561,8 @@ int omap2_clkdm_clk_enable(struct clockdomain *clkdm, struct clk *clk)
 	else
 		omap2_clkdm_wakeup(clkdm);

+	pwrdm_wait_transition(clkdm->pwrdm.ptr);
+
 	return 0;
 }

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