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| author | Daniel Drake <dsd@laptop.org> | 2012-09-04 11:45:32 -0400 |
|---|---|---|
| committer | Florian Tobias Schandinat <FlorianSchandinat@gmx.de> | 2012-09-22 21:31:01 +0000 |
| commit | 012a1211845eab69a5488d59eb87d24cc518c627 (patch) | |
| tree | e2ffa1174de8dd91da1dd71bb108096545fb6c72 | |
| parent | e75478bbd79f4d1694522f1dec7a6cb60c90d3b1 (diff) | |
| download | linux-012a1211845eab69a5488d59eb87d24cc518c627.tar.gz linux-012a1211845eab69a5488d59eb87d24cc518c627.tar.bz2 linux-012a1211845eab69a5488d59eb87d24cc518c627.zip | |
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 <dsd@laptop.org>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Cc: stable@vger.kernel.org
| -rw-r--r-- | drivers/video/via/via_clock.c | 19 |
1 files changed, 19 insertions, 0 deletions
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 <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; + } } |