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powerpc/[booke|4xx]: Don't clobber TCR[WP] when setting TCR[DIE]

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Prevent a kernel panic caused by unintentionally clearing TCR watchdog
bits. At this point in the kernel boot, the watchdog may have 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 476 to reset.

Signed-off-by: Ivan Mikhaylov <ivan@de.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Ivan Mikhaylov 2017-05-19 18:47:05 +03:00 committed by Michael Ellerman
parent 20975a0ae1
commit 6e2f03e292
1 changed files with 11 additions and 3 deletions
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14
arch/powerpc/kernel/time.c
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@ -739,12 +739,20 @@ static int __init get_freq(char *name, int cells, unsigned long *val)
static void start_cpu_decrementer(void)
{
#if defined(CONFIG_BOOKE) || defined(CONFIG_40x)
unsigned int tcr;
/* Clear any pending timer interrupts */
mtspr(SPRN_TSR, TSR_ENW | TSR_WIS | TSR_DIS | TSR_FIS);
/* Enable decrementer interrupt */
mtspr(SPRN_TCR, TCR_DIE);
#endif /* defined(CONFIG_BOOKE) || defined(CONFIG_40x) */
tcr = mfspr(SPRN_TCR);
/*
* The watchdog may have already been enabled by u-boot. So leave
* TRC[WP] (Watchdog Period) alone.
*/
tcr &= TCR_WP_MASK; /* Clear all bits except for TCR[WP] */
tcr |= TCR_DIE; /* Enable decrementer */
mtspr(SPRN_TCR, tcr);
#endif
}
void __init generic_calibrate_decr(void)