From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-dm3nam03on0123.outbound.protection.outlook.com ([104.47.41.123]:2048 "EHLO NAM03-DM3-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S935273AbeCSQNT (ORCPT ); Mon, 19 Mar 2018 12:13:19 -0400 From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" CC: Ivan Mikhaylov , Michael Ellerman , Sasha Levin Subject: [PATCH AUTOSEL for 3.18 057/102] powerpc/[booke|4xx]: Don't clobber TCR[WP] when setting TCR[DIE] Date: Mon, 19 Mar 2018 16:12:40 +0000 Message-ID: <20180319161117.17833-57-alexander.levin@microsoft.com> References: <20180319161117.17833-1-alexander.levin@microsoft.com> In-Reply-To: <20180319161117.17833-1-alexander.levin@microsoft.com> Content-Language: en-US Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org List-ID: From: Ivan Mikhaylov [ 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 Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin --- arch/powerpc/kernel/time.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 7505599c2593..a3d0109becd3 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -646,12 +646,20 @@ static int __init get_freq(char *name, int cells, uns= igned 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); =20 - /* Enable decrementer interrupt */ - mtspr(SPRN_TCR, TCR_DIE); -#endif /* defined(CONFIG_BOOKE) || defined(CONFIG_40x) */ + tcr =3D mfspr(SPRN_TCR); + /* + * The watchdog may have already been enabled by u-boot. So leave + * TRC[WP] (Watchdog Period) alone. + */ + tcr &=3D TCR_WP_MASK; /* Clear all bits except for TCR[WP] */ + tcr |=3D TCR_DIE; /* Enable decrementer */ + mtspr(SPRN_TCR, tcr); +#endif } =20 void __init generic_calibrate_decr(void) --=20 2.14.1