Re: [PATCH] viafb: don't touch clock state on OLPC XO-1.5
From: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Date: 2012-09-23 19:41:18
On 09/04/2012 03:45 PM, Daniel Drake wrote:
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 <redacted>
Applied. Thanks for investigating it. I didn't have the time to look at it due to writing my thesis. Patch looks okay, at least it is a clean workaround. I did Cc stable when committing it to fix older releases. Thanks, Florian Tobias Schandinat
quoted hunk ↗ jump to hunk
--- 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 <linux/kernel.h> #include <linux/via-core.h> +#include <asm/olpc.h> #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; + } }