Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757296Ab2J1Xa6 (ORCPT ); Sun, 28 Oct 2012 19:30:58 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:42248 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757062Ab2J1X2b (ORCPT ); Sun, 28 Oct 2012 19:28:31 -0400 Message-Id: <20121028231544.405054446@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Sun, 28 Oct 2012 23:16:00 +0000 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Daniel Drake , Florian Tobias Schandinat Subject: [ 024/105] viafb: dont touch clock state on OLPC XO-1.5 In-Reply-To: <20121028231536.970033833@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2649 Lines: 78 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Drake commit 012a1211845eab69a5488d59eb87d24cc518c627 upstream. As detailed in the thread titled "viafb PLL/clock tweaking causes XO-1.5 instability," enabling or disabling the IGA1/IGA2 clocks causes occasional stability problems during suspend/resume cycles on this platform. This is rather odd, as the documentation suggests that clocks have two states (on/off) and the default (stable) configuration is configured to enable the clock only when it is needed. However, explicitly enabling *or* disabling the clock triggers this system instability, suggesting that there is a 3rd state at play here. Leaving the clock enable/disable registers alone solves this problem. This fixes spurious reboots during suspend/resume behaviour introduced by commit b692a63a. Signed-off-by: Daniel Drake Signed-off-by: Florian Tobias Schandinat Signed-off-by: Ben Hutchings --- drivers/video/via/via_clock.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/drivers/video/via/via_clock.c b/drivers/video/via/via_clock.c index af8f26b..db1e392 100644 --- a/drivers/video/via/via_clock.c +++ b/drivers/video/via/via_clock.c @@ -25,6 +25,7 @@ #include #include +#include #include "via_clock.h" #include "global.h" #include "debug.h" @@ -289,6 +290,10 @@ static void dummy_set_pll(struct via_pll_config config) printk(KERN_INFO "Using undocumented set PLL.\n%s", via_slap); } +static void noop_set_clock_state(u8 state) +{ +} + void via_clock_init(struct via_clock *clock, int gfx_chip) { switch (gfx_chip) { @@ -346,4 +351,18 @@ void via_clock_init(struct via_clock *clock, int gfx_chip) break; } + + if (machine_is_olpc()) { + /* The OLPC XO-1.5 cannot suspend/resume reliably if the + * IGA1/IGA2 clocks are set as on or off (memory rot + * occasionally happens during suspend under such + * configurations). + * + * The only known stable scenario is to leave this bits as-is, + * which in their default states are documented to enable the + * clock only when it is needed. + */ + clock->set_primary_clock_state = noop_set_clock_state; + clock->set_secondary_clock_state = noop_set_clock_state; + } } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/