Patch "powerpc/[booke|4xx]: Don't clobber TCR[WP] when setting TCR[DIE]" has been added to the 4.9-stable tree

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;a=summary

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 <[email protected]> know about it.

From: Ivan Mikhaylov <[email protected]>
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 <[email protected]>

[ 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.

---
 arch/powerpc/kernel/time.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

@@ -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 [email protected] are

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