From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:56956 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753904AbeDKSlr (ORCPT ); Wed, 11 Apr 2018 14:41:47 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ivan Mikhaylov , Michael Ellerman , Sasha Levin Subject: [PATCH 3.18 055/121] powerpc/[booke|4xx]: Dont clobber TCR[WP] when setting TCR[DIE] Date: Wed, 11 Apr 2018 20:35:58 +0200 Message-Id: <20180411183459.654096592@linuxfoundation.org> In-Reply-To: <20180411183456.195010921@linuxfoundation.org> References: <20180411183456.195010921@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ 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 Signed-off-by: Greg Kroah-Hartman --- 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 @@ -646,12 +646,20 @@ 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)