On Wed, 16 Sep 2009, Kalle Jokiniemi wrote:
> There is a possible race condition in clockdomain
> code handling hw supported idle transitions.
>
> When multiple autodeps dependencies are being added
> or removed, a transition of still remaining dependent
> powerdomain can result in false readings of the
> state counter. This is especially fatal for off mode
> state counter, as it could result in a driver not
> noticing a context loss.
>
> Fixed by disabling hw supported state transitions
> when autodeps are being changed.
>
> Signed-off-by: Kalle Jokiniemi <kalle.jokiniemi@xxxxxxxxx>
Looks great, Kalle, will send this upstream in a fixes series.
- Paul
> ---
> arch/arm/mach-omap2/clockdomain.c | 74 ++++++++++++++++++++++---------------
> 1 files changed, 44 insertions(+), 30 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/clockdomain.c b/arch/arm/mach-omap2/clockdomain.c
> index 4ef7b4f..58aff84 100644
> --- a/arch/arm/mach-omap2/clockdomain.c
> +++ b/arch/arm/mach-omap2/clockdomain.c
> @@ -137,6 +137,36 @@ static void _clkdm_del_autodeps(struct clockdomain *clkdm)
> }
> }
>
> +/*
> + * _omap2_clkdm_set_hwsup - set the hwsup idle transition bit
> + * @clkdm: struct clockdomain *
> + * @enable: int 0 to disable, 1 to enable
> + *
> + * Internal helper for actually switching the bit that controls hwsup
> + * idle transitions for clkdm.
> + */
> +static void _omap2_clkdm_set_hwsup(struct clockdomain *clkdm, int enable)
> +{
> + u32 v;
> +
> + if (cpu_is_omap24xx()) {
> + if (enable)
> + v = OMAP24XX_CLKSTCTRL_ENABLE_AUTO;
> + else
> + v = OMAP24XX_CLKSTCTRL_DISABLE_AUTO;
> + } else if (cpu_is_omap34xx()) {
> + if (enable)
> + v = OMAP34XX_CLKSTCTRL_ENABLE_AUTO;
> + else
> + v = OMAP34XX_CLKSTCTRL_DISABLE_AUTO;
> + } else {
> + BUG();
> + }
> +
> + cm_rmw_mod_reg_bits(clkdm->clktrctrl_mask,
> + v << __ffs(clkdm->clktrctrl_mask),
> + clkdm->pwrdm.ptr->prcm_offs, CM_CLKSTCTRL);
> +}
>
> static struct clockdomain *_clkdm_lookup(const char *name)
> {
> @@ -456,8 +486,6 @@ int omap2_clkdm_wakeup(struct clockdomain *clkdm)
> */
> void omap2_clkdm_allow_idle(struct clockdomain *clkdm)
> {
> - u32 v;
> -
> if (!clkdm)
> return;
>
> @@ -473,18 +501,7 @@ void omap2_clkdm_allow_idle(struct clockdomain *clkdm)
> if (atomic_read(&clkdm->usecount) > 0)
> _clkdm_add_autodeps(clkdm);
>
> - if (cpu_is_omap24xx())
> - v = OMAP24XX_CLKSTCTRL_ENABLE_AUTO;
> - else if (cpu_is_omap34xx())
> - v = OMAP34XX_CLKSTCTRL_ENABLE_AUTO;
> - else
> - BUG();
> -
> -
> - cm_rmw_mod_reg_bits(clkdm->clktrctrl_mask,
> - v << __ffs(clkdm->clktrctrl_mask),
> - clkdm->pwrdm.ptr->prcm_offs,
> - CM_CLKSTCTRL);
> + _omap2_clkdm_set_hwsup(clkdm, 1);
>
> pwrdm_clkdm_state_switch(clkdm);
> }
> @@ -500,8 +517,6 @@ void omap2_clkdm_allow_idle(struct clockdomain *clkdm)
> */
> void omap2_clkdm_deny_idle(struct clockdomain *clkdm)
> {
> - u32 v;
> -
> if (!clkdm)
> return;
>
> @@ -514,16 +529,7 @@ void omap2_clkdm_deny_idle(struct clockdomain *clkdm)
> pr_debug("clockdomain: disabling automatic idle transitions for %s\n",
> clkdm->name);
>
> - if (cpu_is_omap24xx())
> - v = OMAP24XX_CLKSTCTRL_DISABLE_AUTO;
> - else if (cpu_is_omap34xx())
> - v = OMAP34XX_CLKSTCTRL_DISABLE_AUTO;
> - else
> - BUG();
> -
> - cm_rmw_mod_reg_bits(clkdm->clktrctrl_mask,
> - v << __ffs(clkdm->clktrctrl_mask),
> - clkdm->pwrdm.ptr->prcm_offs, CM_CLKSTCTRL);
> + _omap2_clkdm_set_hwsup(clkdm, 0);
>
> if (atomic_read(&clkdm->usecount) > 0)
> _clkdm_del_autodeps(clkdm);
> @@ -569,10 +575,14 @@ int omap2_clkdm_clk_enable(struct clockdomain *clkdm, struct clk *clk)
> v = omap2_clkdm_clktrctrl_read(clkdm);
>
> if ((cpu_is_omap34xx() && v == OMAP34XX_CLKSTCTRL_ENABLE_AUTO) ||
> - (cpu_is_omap24xx() && v == OMAP24XX_CLKSTCTRL_ENABLE_AUTO))
> + (cpu_is_omap24xx() && v == OMAP24XX_CLKSTCTRL_ENABLE_AUTO)) {
> + /* Disable HW transitions when we are changing deps */
> + _omap2_clkdm_set_hwsup(clkdm, 0);
> _clkdm_add_autodeps(clkdm);
> - else
> + _omap2_clkdm_set_hwsup(clkdm, 1);
> + } else {
> omap2_clkdm_wakeup(clkdm);
> + }
>
> pwrdm_wait_transition(clkdm->pwrdm.ptr);
> pwrdm_clkdm_state_switch(clkdm);
> @@ -623,10 +633,14 @@ int omap2_clkdm_clk_disable(struct clockdomain *clkdm, struct clk *clk)
> v = omap2_clkdm_clktrctrl_read(clkdm);
>
> if ((cpu_is_omap34xx() && v == OMAP34XX_CLKSTCTRL_ENABLE_AUTO) ||
> - (cpu_is_omap24xx() && v == OMAP24XX_CLKSTCTRL_ENABLE_AUTO))
> + (cpu_is_omap24xx() && v == OMAP24XX_CLKSTCTRL_ENABLE_AUTO)) {
> + /* Disable HW transitions when we are changing deps */
> + _omap2_clkdm_set_hwsup(clkdm, 0);
> _clkdm_del_autodeps(clkdm);
> - else
> + _omap2_clkdm_set_hwsup(clkdm, 1);
> + } else {
> omap2_clkdm_sleep(clkdm);
> + }
>
> pwrdm_clkdm_state_switch(clkdm);
>
> --
> 1.5.4.3
>
- Paul
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