linux-kernel - Re: [PATCH] ARM: at91: panic when the mck rate is zero

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Message-ID: <20140320164003.GV12021@piout.net>
Date:	Thu, 20 Mar 2014 17:40:04 +0100
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Boris BREZILLON <b.brezillon.dev@...il.com>
Cc:	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: at91: panic when the mck rate is zero

On 20/03/2014 at 17:34:09 +0100, Boris BREZILLON wrote :
> Le 20/03/2014 17:14, Alexandre Belloni a écrit :
> >If the mck rate is zero, we'll hit the following warning:
> >
> >WARNING: CPU: 0 PID: 0 at arch/arm/mach-at91/at91sam926x_time.c:257 at91sam926x_pit_init+0x13c/0x260()
> >
> >But the kernel will continue to try booting and face a lot of divisions by zero
> >when trying to handle the various clocks.
> >
> >Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> >---
> >  arch/arm/mach-at91/at91sam926x_time.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> >diff --git a/arch/arm/mach-at91/at91sam926x_time.c b/arch/arm/mach-at91/at91sam926x_time.c
> >index 0f04ffe9c5a8..f060f6371392 100644
> >--- a/arch/arm/mach-at91/at91sam926x_time.c
> >+++ b/arch/arm/mach-at91/at91sam926x_time.c
> >@@ -250,6 +250,8 @@ void __init at91sam926x_pit_init(void)
> >  	if (IS_ERR(mck))
> >  		panic("AT91: PIT: Unable to get mck clk\n");
> >  	pit_rate = clk_get_rate(mck) / 16;
> >+	if (pit_rate == 0)
> >+		panic("AT91: PIT: can't continue, mck rate is zero\n");
> You're testing pit_rate why not printing:
> 
> "AT91: PIT: can't continue, *pit* rate is zero\n"
> 

pit_rate is zero because mck is zero I just didn't want to introduce a
new variable or another call to clk_get_rate(mck). I don't have any
strong opinion about that either so I can definitely make that change.


-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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