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Message-ID: <1495189806.3092.111.camel@kernel.crashing.org>
Subject: Re: [PATCH 4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of
 whole rewrite
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Ivan Mikhaylov <ivan@de.ibm.com>, Alistair Popple <alistair@popple.id.au>,
 Matt Porter <mporter@kernel.crashing.org>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Joel
 Stanley <joel@ozlabs.au.ibm.com>, Paul Mackerras <paulus@samba.org>,
 Michael Ellerman <mpe@ellerman.id.au>
Date: Fri, 19 May 2017 20:30:06 +1000
In-Reply-To: <20170515130754.59363-5-ivan@de.ibm.com>
References: <20170515130754.59363-5-ivan@de.ibm.com>
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On Mon, 2017-05-15 at 16:07 +0300, Ivan Mikhaylov wrote:
> +#ifdef CONFIG_FSP2
> +       /*
> +        * Prevent a kernel panic caused by unintentionally clearing TCR
> +        * watchdog bits.  At this point in the kernel boot, the watchdog has
> +        * already been enabled by u-boot.  The original code's attempt to
> +        * write to the TCR register results in an inadvertent clearing of the
> +        * watchdog configuration bits, causing the 440 to reset.
> +        */
> +       tcr = mfspr(SPRN_TCR);
> +       tcr &= TCR_WP_MASK; /* clear all bits except for TCR[WP] */
> +       tcr |= TCR_DIE; /* enable decrementer */
> +       mtspr(SPRN_TCR, tcr);
> +#else

This should be a runtime test, not a compile time option.

Cheers,
Ben.