This is a note to let you know that I've just added the patch titled

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

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: powerpc-don-t-clobber-tcr-when-setting-tcr.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Mon Apr 9 17:09:24 CEST 2018

From: Ivan Mikhaylov ivan@de.ibm.com Date: Fri, 19 May 2017 18:47:05 +0300 Subject: powerpc/[booke|4xx]: Don't clobber TCR[WP] when setting TCR[DIE]

From: Ivan Mikhaylov ivan@de.ibm.com

[ Upstream commit 6e2f03e292ef46eed2b31b0a344a91d514f9cd81 ]

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 Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/kernel/time.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)

--- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -719,12 +719,20 @@ static int __init get_freq(char *name, i 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)

Patches currently in stable-queue which might be from ivan@de.ibm.com are

queue-4.9/powerpc-don-t-clobber-tcr-when-setting-tcr.patch