Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756278Ab2KZRBt (ORCPT ); Mon, 26 Nov 2012 12:01:49 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:47144 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755833Ab2KZRBp (ORCPT ); Mon, 26 Nov 2012 12:01:45 -0500 From: Herton Ronaldo Krzesinski To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Daniel Drake , Florian Tobias Schandinat , Herton Ronaldo Krzesinski Subject: [PATCH 032/270] viafb: don't touch clock state on OLPC XO-1.5 Date: Mon, 26 Nov 2012 14:55:22 -0200 Message-Id: <1353949160-26803-33-git-send-email-herton.krzesinski@canonical.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1353949160-26803-1-git-send-email-herton.krzesinski@canonical.com> References: <1353949160-26803-1-git-send-email-herton.krzesinski@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2689 Lines: 79 3.5.7u1 -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: Herton Ronaldo Krzesinski --- 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; + } } -- 1.7.9.5 -- 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/