From 012a1211845eab69a5488d59eb87d24cc518c627 Mon Sep 17 00:00:00 2001 From: Daniel Drake Date: Tue, 4 Sep 2012 11:45:32 -0400 Subject: [PATCH] viafb: don't touch clock state on OLPC XO-1.5 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 Cc: stable@vger.kernel.org --- 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 af8f26b643c1..db1e39277e32 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; + } } -- 2.34.1