From 60cf09e45fbcbbbb3162f02e0923a25ae7f5627e Mon Sep 17 00:00:00 2001 From: Shawn Lin Date: Fri, 9 Mar 2018 09:51:03 +0800 Subject: [PATCH] clk: rockchip: Restore the clock phase after the rate was changed There are many factors affecting the clock phase, including clock rate, temperature, logic voltage and silicon process, etc. But clock rate is the most significant one here, and the driver should be aware of the change of the clock rate. As mmc controller need a fixed phase after tuning was completed, at least before explicitly doing re-tune, so this patch try to restore the clock phase by monitoring the event of rate change. Signed-off-by: Shawn Lin Signed-off-by: Heiko Stuebner --- drivers/clk/rockchip/clk-mmc-phase.c | 39 +++++++++++++++++++++++++++- 1 file changed, 38 insertions(+), 1 deletion(-) diff --git a/drivers/clk/rockchip/clk-mmc-phase.c b/drivers/clk/rockchip/clk-mmc-phase.c index fe7d9ed1d436..dc4c227732bd 100644 --- a/drivers/clk/rockchip/clk-mmc-phase.c +++ b/drivers/clk/rockchip/clk-mmc-phase.c @@ -25,6 +25,8 @@ struct rockchip_mmc_clock { void __iomem *reg; int id; int shift; + int cached_phase; + struct notifier_block clk_rate_change_nb; }; #define to_mmc_clock(_hw) container_of(_hw, struct rockchip_mmc_clock, hw) @@ -162,6 +164,29 @@ static const struct clk_ops rockchip_mmc_clk_ops = { .set_phase = rockchip_mmc_set_phase, }; +#define to_rockchip_mmc_clock(x) \ + container_of(x, struct rockchip_mmc_clock, clk_rate_change_nb) +static int rockchip_mmc_clk_rate_notify(struct notifier_block *nb, + unsigned long event, void *data) +{ + struct rockchip_mmc_clock *mmc_clock = to_rockchip_mmc_clock(nb); + + /* + * rockchip_mmc_clk is mostly used by mmc controllers to sample + * the intput data, which expects the fixed phase after the tuning + * process. However if the clock rate is changed, the phase is stale + * and may break the data sampling. So here we try to restore the phase + * for that case. + */ + if (event == PRE_RATE_CHANGE) + mmc_clock->cached_phase = + rockchip_mmc_get_phase(&mmc_clock->hw); + else if (event == POST_RATE_CHANGE) + rockchip_mmc_set_phase(&mmc_clock->hw, mmc_clock->cached_phase); + + return NOTIFY_DONE; +} + struct clk *rockchip_clk_register_mmc(const char *name, const char *const *parent_names, u8 num_parents, void __iomem *reg, int shift) @@ -169,6 +194,7 @@ struct clk *rockchip_clk_register_mmc(const char *name, struct clk_init_data init; struct rockchip_mmc_clock *mmc_clock; struct clk *clk; + int ret; mmc_clock = kmalloc(sizeof(*mmc_clock), GFP_KERNEL); if (!mmc_clock) @@ -186,7 +212,18 @@ struct clk *rockchip_clk_register_mmc(const char *name, clk = clk_register(NULL, &mmc_clock->hw); if (IS_ERR(clk)) - kfree(mmc_clock); + goto err_register; + + mmc_clock->clk_rate_change_nb.notifier_call = + &rockchip_mmc_clk_rate_notify; + ret = clk_notifier_register(clk, &mmc_clock->clk_rate_change_nb); + if (ret) + goto err_notifier; return clk; +err_notifier: + clk_unregister(clk); +err_register: + kfree(mmc_clock); + return clk; }