diff --git a/drivers/clk/sunxi-ng/ccu_common.c b/drivers/clk/sunxi-ng/ccu_common.c index 8a47bafd78905bce849235d791f1469d448afcc9..9d8724715a4352ddd07a411945bc1cd58367053d 100644 --- a/drivers/clk/sunxi-ng/ccu_common.c +++ b/drivers/clk/sunxi-ng/ccu_common.c @@ -14,11 +14,13 @@ * GNU General Public License for more details. */ +#include #include #include #include #include "ccu_common.h" +#include "ccu_gate.h" #include "ccu_reset.h" static DEFINE_SPINLOCK(ccu_lock); @@ -39,6 +41,53 @@ void ccu_helper_wait_for_lock(struct ccu_common *common, u32 lock) WARN_ON(readl_relaxed_poll_timeout(addr, reg, reg & lock, 100, 70000)); } +/* + * This clock notifier is called when the frequency of a PLL clock is + * changed. In common PLL designs, changes to the dividers take effect + * almost immediately, while changes to the multipliers (implemented + * as dividers in the feedback loop) take a few cycles to work into + * the feedback loop for the PLL to stablize. + * + * Sometimes when the PLL clock rate is changed, the decrease in the + * divider is too much for the decrease in the multiplier to catch up. + * The PLL clock rate will spike, and in some cases, might lock up + * completely. + * + * This notifier callback will gate and then ungate the clock, + * effectively resetting it, so it proceeds to work. Care must be + * taken to reparent consumers to other temporary clocks during the + * rate change, and that this notifier callback must be the first + * to be registered. + */ +static int ccu_pll_notifier_cb(struct notifier_block *nb, + unsigned long event, void *data) +{ + struct ccu_pll_nb *pll = to_ccu_pll_nb(nb); + int ret = 0; + + if (event != POST_RATE_CHANGE) + goto out; + + ccu_gate_helper_disable(pll->common, pll->enable); + + ret = ccu_gate_helper_enable(pll->common, pll->enable); + if (ret) + goto out; + + ccu_helper_wait_for_lock(pll->common, pll->lock); + +out: + return notifier_from_errno(ret); +} + +int ccu_pll_notifier_register(struct ccu_pll_nb *pll_nb) +{ + pll_nb->clk_nb.notifier_call = ccu_pll_notifier_cb; + + return clk_notifier_register(pll_nb->common->hw.clk, + &pll_nb->clk_nb); +} + int sunxi_ccu_probe(struct device_node *node, void __iomem *reg, const struct sunxi_ccu_desc *desc) { diff --git a/drivers/clk/sunxi-ng/ccu_common.h b/drivers/clk/sunxi-ng/ccu_common.h index 73d81dc58fc5ad91f8a293530aa89e2b22fcbdb3..d6fdd7a789aa746a72f939fb51c552004941fd37 100644 --- a/drivers/clk/sunxi-ng/ccu_common.h +++ b/drivers/clk/sunxi-ng/ccu_common.h @@ -83,6 +83,18 @@ struct sunxi_ccu_desc { void ccu_helper_wait_for_lock(struct ccu_common *common, u32 lock); +struct ccu_pll_nb { + struct notifier_block clk_nb; + struct ccu_common *common; + + u32 enable; + u32 lock; +}; + +#define to_ccu_pll_nb(_nb) container_of(_nb, struct ccu_pll_nb, clk_nb) + +int ccu_pll_notifier_register(struct ccu_pll_nb *pll_nb); + int sunxi_ccu_probe(struct device_node *node, void __iomem *reg, const struct sunxi_ccu_desc *desc);