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 <dsd@xxxxxxxxxx>
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
> ---
> 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;
> + }
> }
--
To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
