From: Yao Zi Date: Thu, 20 Nov 2025 13:14:15 +0000 (+0000) Subject: clk: thead: th1520-ap: Support CPU frequency scaling X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=baf4fc7c03bd0f68c768cfe27829674bd060c6b4;p=thirdparty%2Fkernel%2Fstable.git clk: thead: th1520-ap: Support CPU frequency scaling On TH1520 SoC, c910_clk feeds the CPU cluster. It could be glitchlessly reparented to one of the two PLLs: either to cpu_pll0 indirectly through c910_i0_clk, or to cpu_pll1 directly. To achieve glitchless rate change, customized clock operations are implemented for c910_clk: on rate change, the PLL not currently in use is configured to the requested rate first, then c910_clk reparents to it. Additionally, c910_bus_clk, which in turn takes c910_clk as parent, has a frequency limit of 750MHz. A clock notifier is registered on c910_clk to adjust c910_bus_clk on c910_clk rate change. Reviewed-by: Drew Fustini Signed-off-by: Yao Zi Signed-off-by: Drew Fustini --- diff --git a/drivers/clk/thead/clk-th1520-ap.c b/drivers/clk/thead/clk-th1520-ap.c index 79f001a047b2..3a6847f1c950 100644 --- a/drivers/clk/thead/clk-th1520-ap.c +++ b/drivers/clk/thead/clk-th1520-ap.c @@ -7,9 +7,11 @@ #include #include +#include #include #include #include +#include #include #include #include @@ -34,6 +36,9 @@ #define TH1520_PLL_LOCK_TIMEOUT_US 44 #define TH1520_PLL_STABLE_DELAY_US 30 +/* c910_bus_clk must be kept below 750MHz for stability */ +#define TH1520_C910_BUS_MAX_RATE (750 * 1000 * 1000) + struct ccu_internal { u8 shift; u8 width; @@ -472,6 +477,72 @@ static const struct clk_ops clk_pll_ops = { .set_rate = ccu_pll_set_rate, }; +/* + * c910_clk could be reparented glitchlessly for DVFS. There are two parents, + * - c910_i0_clk, derived from cpu_pll0_clk or osc_24m. + * - cpu_pll1_clk, which provides the exact same set of rates as cpu_pll0_clk. + * + * During rate setting, always forward the request to the unused parent, and + * then switch c910_clk to it to avoid glitch. + */ +static u8 c910_clk_get_parent(struct clk_hw *hw) +{ + return clk_mux_ops.get_parent(hw); +} + +static int c910_clk_set_parent(struct clk_hw *hw, u8 index) +{ + return clk_mux_ops.set_parent(hw, index); +} + +static unsigned long c910_clk_recalc_rate(struct clk_hw *hw, + unsigned long parent_rate) +{ + return parent_rate; +} + +static int c910_clk_determine_rate(struct clk_hw *hw, + struct clk_rate_request *req) +{ + u8 alt_parent_index = !c910_clk_get_parent(hw); + struct clk_hw *alt_parent; + + alt_parent = clk_hw_get_parent_by_index(hw, alt_parent_index); + + req->rate = clk_hw_round_rate(alt_parent, req->rate); + req->best_parent_hw = alt_parent; + req->best_parent_rate = req->rate; + + return 0; +} + +static int c910_clk_set_rate(struct clk_hw *hw, unsigned long rate, + unsigned long parent_rate) +{ + return -EOPNOTSUPP; +} + +static int c910_clk_set_rate_and_parent(struct clk_hw *hw, unsigned long rate, + unsigned long parent_rate, u8 index) +{ + struct clk_hw *parent = clk_hw_get_parent_by_index(hw, index); + + clk_set_rate(parent->clk, parent_rate); + + c910_clk_set_parent(hw, index); + + return 0; +} + +static const struct clk_ops c910_clk_ops = { + .get_parent = c910_clk_get_parent, + .set_parent = c910_clk_set_parent, + .recalc_rate = c910_clk_recalc_rate, + .determine_rate = c910_clk_determine_rate, + .set_rate = c910_clk_set_rate, + .set_rate_and_parent = c910_clk_set_rate_and_parent, +}; + static const struct clk_parent_data osc_24m_clk[] = { { .index = 0 } }; @@ -672,7 +743,8 @@ static const struct clk_parent_data c910_i0_parents[] = { static struct ccu_mux c910_i0_clk = { .clkid = CLK_C910_I0, .reg = 0x100, - .mux = TH_CCU_MUX("c910-i0", c910_i0_parents, 1, 1), + .mux = TH_CCU_MUX_FLAGS("c910-i0", c910_i0_parents, 1, 1, + CLK_SET_RATE_PARENT, CLK_MUX_ROUND_CLOSEST), }; static const struct clk_parent_data c910_parents[] = { @@ -683,7 +755,14 @@ static const struct clk_parent_data c910_parents[] = { static struct ccu_mux c910_clk = { .clkid = CLK_C910, .reg = 0x100, - .mux = TH_CCU_MUX("c910", c910_parents, 0, 1), + .mux = { + .mask = BIT(0), + .shift = 0, + .hw.init = CLK_HW_INIT_PARENTS_DATA("c910", + c910_parents, + &c910_clk_ops, + CLK_SET_RATE_PARENT), + }, }; static struct ccu_div c910_bus_clk = { @@ -1372,11 +1451,69 @@ static const struct th1520_plat_data th1520_vo_platdata = { .nr_gate_clks = ARRAY_SIZE(th1520_vo_gate_clks), }; +/* + * Maintain clock rate of c910_bus_clk below TH1520_C910_BUS_MAX_RATE (750MHz) + * when its parent, c910_clk, changes the rate. + * + * Additionally, TRM is unclear about c910_bus_clk behavior when the divisor is + * set below 2, thus we should ensure the new divisor stays in (2, MAXDIVISOR). + */ +static unsigned long c910_bus_clk_divisor(struct ccu_div *cd, + unsigned long parent_rate) +{ + return clamp(DIV_ROUND_UP(parent_rate, TH1520_C910_BUS_MAX_RATE), + 2U, 1U << cd->div.width); +} + +static int c910_clk_notifier_cb(struct notifier_block *nb, + unsigned long action, void *data) +{ + struct clk_notifier_data *cnd = data; + unsigned long new_divisor, ref_rate; + + if (action != PRE_RATE_CHANGE && action != POST_RATE_CHANGE) + return NOTIFY_DONE; + + new_divisor = c910_bus_clk_divisor(&c910_bus_clk, cnd->new_rate); + + if (cnd->new_rate > cnd->old_rate) { + /* + * Scaling up. Adjust c910_bus_clk divisor + * - before c910_clk rate change to ensure the constraints + * aren't broken after scaling to higher rates, + * - after c910_clk rate change to keep c910_bus_clk as high as + * possible + */ + ref_rate = action == PRE_RATE_CHANGE ? + cnd->old_rate : cnd->new_rate; + clk_set_rate(c910_bus_clk.common.hw.clk, + ref_rate / new_divisor); + } else if (cnd->new_rate < cnd->old_rate && + action == POST_RATE_CHANGE) { + /* + * Scaling down. Adjust c910_bus_clk divisor only after + * c910_clk rate change to keep c910_bus_clk as high as + * possible, Scaling down never breaks the constraints. + */ + clk_set_rate(c910_bus_clk.common.hw.clk, + cnd->new_rate / new_divisor); + } else { + return NOTIFY_DONE; + } + + return NOTIFY_OK; +} + +static struct notifier_block c910_clk_notifier = { + .notifier_call = c910_clk_notifier_cb, +}; + static int th1520_clk_probe(struct platform_device *pdev) { const struct th1520_plat_data *plat_data; struct device *dev = &pdev->dev; struct clk_hw_onecell_data *priv; + struct clk *notifier_clk; struct regmap *map; void __iomem *base; @@ -1463,6 +1600,13 @@ static int th1520_clk_probe(struct platform_device *pdev) ret = devm_clk_hw_register(dev, &emmc_sdio_ref_clk.hw); if (ret) return ret; + + notifier_clk = devm_clk_hw_get_clk(dev, &c910_clk.mux.hw, + "dvfs"); + ret = devm_clk_notifier_register(dev, notifier_clk, + &c910_clk_notifier); + if (ret) + return ret; } ret = devm_of_clk_add_hw_provider(dev, of_clk_hw_onecell_get, priv);