The K210 PLL clock implements a mux with a set_parent hook, but doesn't provide a determine_rate implementation.
This is a bit odd, since set_parent() is there to, as its name implies, change the parent of a clock. However, the most likely candidate to trigger that parent change is a call to clk_set_rate(), with determine_rate() figuring out which parent is the best suited for a given rate.
The other trigger would be a call to clk_set_parent(), but it's far less used, and it doesn't look like there's any obvious user for that clock.
So, the set_parent hook is effectively unused, possibly because of an oversight. However, it could also be an explicit decision by the original author to avoid any reparenting but through an explicit call to clk_set_parent().
The latter case would be equivalent to setting the flag CLK_SET_RATE_NO_REPARENT, together with setting our determine_rate hook to __clk_mux_determine_rate(). Indeed, if no determine_rate implementation is provided, clk_round_rate() (through clk_core_round_rate_nolock()) will call itself on the parent if CLK_SET_RATE_PARENT is set, and will not change the clock rate otherwise. __clk_mux_determine_rate() has the exact same behavior when CLK_SET_RATE_NO_REPARENT is set.
And if it was an oversight, then we are at least explicit about our behavior now and it can be further refined down the line.
Signed-off-by: Maxime Ripard maxime@cerno.tech --- drivers/clk/clk-k210.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/drivers/clk/clk-k210.c b/drivers/clk/clk-k210.c index 67a7cb3503c3..279931a38127 100644 --- a/drivers/clk/clk-k210.c +++ b/drivers/clk/clk-k210.c @@ -537,6 +537,7 @@ static const struct clk_ops k210_pll2_ops = { .disable = k210_pll_disable, .is_enabled = k210_pll_is_enabled, .recalc_rate = k210_pll_get_rate, + .determine_rate = __clk_mux_determine_rate, .set_parent = k210_pll2_set_parent, .get_parent = k210_pll2_get_parent, }; @@ -544,7 +545,8 @@ static const struct clk_ops k210_pll2_ops = { static int __init k210_register_pll(struct device_node *np, struct k210_sysclk *ksc, enum k210_pll_id pllid, const char *name, - int num_parents, const struct clk_ops *ops) + int num_parents, const struct clk_ops *ops, + unsigned long flags) { struct k210_pll *pll = &ksc->plls[pllid]; struct clk_init_data init = {}; @@ -558,6 +560,7 @@ static int __init k210_register_pll(struct device_node *np, init.parent_data = parent_data; init.num_parents = num_parents; init.ops = ops; + init.flags = flags;
pll->hw.init = &init; pll->ksc = ksc; @@ -574,19 +577,20 @@ static int __init k210_register_plls(struct device_node *np, k210_init_pll(ksc->regs, i, &ksc->plls[i]);
/* PLL0 and PLL1 only have IN0 as parent */ - ret = k210_register_pll(np, ksc, K210_PLL0, "pll0", 1, &k210_pll_ops); + ret = k210_register_pll(np, ksc, K210_PLL0, "pll0", 1, &k210_pll_ops, 0); if (ret) { pr_err("%pOFP: register PLL0 failed\n", np); return ret; } - ret = k210_register_pll(np, ksc, K210_PLL1, "pll1", 1, &k210_pll_ops); + ret = k210_register_pll(np, ksc, K210_PLL1, "pll1", 1, &k210_pll_ops, 0); if (ret) { pr_err("%pOFP: register PLL1 failed\n", np); return ret; }
/* PLL2 has IN0, PLL0 and PLL1 as parents */ - ret = k210_register_pll(np, ksc, K210_PLL2, "pll2", 3, &k210_pll2_ops); + ret = k210_register_pll(np, ksc, K210_PLL2, "pll2", 3, &k210_pll2_ops, + CLK_SET_RATE_NO_REPARENT); if (ret) { pr_err("%pOFP: register PLL2 failed\n", np); return ret;