Messages in this thread Patch in this message | | | From | Michael Ellerman <> | Subject | Re: [PATCH 4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of whole rewrite | Date | Fri, 26 May 2017 20:37:25 +1000 |
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Michael Ellerman <mpe@ellerman.id.au> writes:
> Ivan Mikhaylov <ivan@de.ibm.com> writes: >> >> From my point of view it's possible. I've checked docu and on idea >> it should be possible cause WP is only affecting watchdog ping time. > > The question is, is there any chance that leaving those bits set on > another platform will cause a problem? > > ie. on existing machines we always clear those bits, is it OK that we > will now start leaving those bits with whatever value they had.
I came up with the patch below (more or less your v2), if it breaks something we can always fix it.
cheers
commit c80409358a9c91e1f6b18353dad939b851bb3522 Author: Ivan Mikhaylov <ivan@de.ibm.com> Date: Fri May 19 18:47:05 2017 +0300
powerpc/[booke|4xx]: Don't clobber TCR[WP] when setting TCR[DIE] 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>
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 2b33cfaac7b8..60714b8c9a2f 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -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)
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