Add a common clock driver for NCO blocks found on Apple SoCs where they
are typically the generators of audio clocks.
Signed-off-by: Martin Povišer <povik+lin@xxxxxxxxxxxxxx>
---
drivers/clk/Kconfig | 9 +
drivers/clk/Makefile | 1 +
drivers/clk/clk-apple-nco.c | 340 ++++++++++++++++++++++++++++++++++++
3 files changed, 350 insertions(+)
create mode 100644 drivers/clk/clk-apple-nco.c
diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index ad4256d54361..af4d037e18e3 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -59,6 +59,15 @@ config LMK04832
Say yes here to build support for Texas Instruments' LMK04832 Ultra
Low-Noise JESD204B Compliant Clock Jitter Cleaner With Dual Loop PLLs
+config COMMON_CLK_APPLE_NCO
+ bool "Clock driver for Apple SoC NCOs"
+ depends on ARCH_APPLE || COMPILE_TEST
+ default ARCH_APPLE
+ help
+ This driver supports NCO (Numerically Controlled Oscillator) blocks
+ found on Apple SoCs such as t8103 (M1). The blocks are typically
+ generators of audio clocks.
+
config COMMON_CLK_MAX77686
tristate "Clock driver for Maxim 77620/77686/77802 MFD"
depends on MFD_MAX77686 || MFD_MAX77620 || COMPILE_TEST
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 16e588630472..e95e702bdaeb 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -17,6 +17,7 @@ endif
# hardware specific clock types
# please keep this section sorted lexicographically by file path name
+obj-$(CONFIG_COMMON_CLK_APPLE_NCO) += clk-apple-nco.o
obj-$(CONFIG_MACH_ASM9260) += clk-asm9260.o
obj-$(CONFIG_COMMON_CLK_AXI_CLKGEN) += clk-axi-clkgen.o
obj-$(CONFIG_ARCH_AXXIA) += clk-axm5516.o
diff --git a/drivers/clk/clk-apple-nco.c b/drivers/clk/clk-apple-nco.c
new file mode 100644
index 000000000000..593f5b5ce5b7
--- /dev/null
+++ b/drivers/clk/clk-apple-nco.c
@@ -0,0 +1,340 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Driver for an SoC block (Numerically Controlled Oscillator)
+ * found on t8103 (M1) and other Apple chips
+ *
+ * Copyright (C) The Asahi Linux Contributors
+ */
+
+#include <linux/bits.h>
+#include <linux/clk-provider.h>
+#include <linux/io.h>
+#include <linux/math64.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_clk.h>
+#include <linux/platform_device.h>
+#include <linux/spinlock.h>
+
+#define NCO_CHANNEL_STRIDE 0x4000
+#define NCO_CHANNEL_REGSIZE 20
+
+#define REG_CTRL 0
+#define CTRL_ENABLE BIT(31)
+#define REG_DIV 4
+#define DIV_FINE GENMASK(1, 0)
+#define DIV_COARSE GENMASK(12, 2)
+#define REG_INC1 8
+#define REG_INC2 12
+#define REG_ACCINIT 16
+
+/*
+ * Theory of operation (postulated)
+ *
+ * The REG_DIV register indirectly expresses a base integer divisor, roughly
+ * corresponding to twice the desired ratio of input to output clock. This
+ * base divisor is adjusted on a cycle-by-cycle basis based on the state of a
+ * 32-bit phase accumulator to achieve a desired precise clock ratio over the
+ * long term.
+ *
+ * Specifically an output clock cycle is produced after (REG_DIV divisor)/2
+ * or (REG_DIV divisor + 1)/2 input cycles, the latter taking effect when top
+ * bit of the 32-bit accumulator is set. The accumulator is incremented each
+ * produced output cycle, by the value from either REG_INC1 or REG_INC2, which
+ * of the two is selected depending again on the accumulator's current top bit.
+ *
+ * Because the NCO hardware implements counting of input clock cycles in part
+ * in a Galois linear-feedback shift register, the higher bits of divisor
+ * are programmed into REG_DIV by picking an appropriate LFSR state. See
+ * nco_compute_tables/nco_div_translate for details on this.
+ */
+
+struct nco_tables;
+
+struct nco_channel {
+ void __iomem *base;
+ struct nco_tables *tbl;
+ struct clk_hw hw;
+
+ spinlock_t lock;
+};
+
+#define to_nco_channel(_hw) container_of(_hw, struct nco_channel, hw)
+
+#define LFSR_POLY 0xa01
+#define LFSR_INIT 0x7ff
+#define LFSR_LEN 11
+#define LFSR_PERIOD ((1 << LFSR_LEN) - 1)
+#define LFSR_TBLSIZE (1 << LFSR_LEN)
+
+/* The minimal attainable coarse divisor (first value in table) */
+#define COARSE_DIV_OFFSET 2
+
+struct nco_tables {
+ u16 fwd[LFSR_TBLSIZE];
+ u16 inv[LFSR_TBLSIZE];
+};
+
+static void nco_enable_nolock(struct clk_hw *hw);
+static void nco_disable_nolock(struct clk_hw *hw);
+static int nco_is_enabled(struct clk_hw *hw);
+
+static void nco_compute_tables(struct nco_tables *tbl)
+{
+ int i;
+ u32 state = LFSR_INIT;
+
+ /*
+ * Go through the states of a Galois LFSR and build
+ * a coarse divisor translation table.
+ */
+ for (i = LFSR_PERIOD; i > 0; i--) {
+ if (state & 1)
+ state = (state >> 1) ^ (LFSR_POLY >> 1);
+ else
+ state = (state >> 1);
+ tbl->fwd[i] = state;
+ tbl->inv[state] = i;
+ }
+
+ /* Zero value is special-cased */
+ tbl->fwd[0] = 0;
+ tbl->inv[0] = 0;
+}
+
+static bool nco_div_out_of_range(unsigned int div)
+{
+ unsigned int coarse = div / 4;
+ return coarse < COARSE_DIV_OFFSET ||
+ coarse >= COARSE_DIV_OFFSET + LFSR_TBLSIZE;
+}
+
+static u32 nco_div_translate(struct nco_tables *tbl, unsigned int div)
+{
+ unsigned int coarse = div / 4;
+
+ if (WARN_ON(nco_div_out_of_range(div)))
+ return 0;
+
+ return FIELD_PREP(DIV_COARSE, tbl->fwd[coarse - COARSE_DIV_OFFSET]) |
+ FIELD_PREP(DIV_FINE, div % 4);
+}
+
+static unsigned int nco_div_translate_inv(struct nco_tables *tbl, u32 regval)
+{
+ unsigned int coarse, fine;
+
+ coarse = tbl->inv[FIELD_GET(DIV_COARSE, regval)] + COARSE_DIV_OFFSET;
+ fine = FIELD_GET(DIV_FINE, regval);
+
+ return coarse * 4 + fine;
+}
+
+static int nco_set_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long parent_rate)
+{
+ struct nco_channel *chan = to_nco_channel(hw);
+ unsigned long flags;
+ u32 div;
+ s32 inc1, inc2;
+ bool was_enabled;
+
+ div = 2 * parent_rate / rate;
+ inc1 = 2 * parent_rate - div * rate;
+ inc2 = -((s32) (rate - inc1));
+
+ if (nco_div_out_of_range(div))
+ return -EINVAL;
+
+ div = nco_div_translate(chan->tbl, div);
+
+ spin_lock_irqsave(&chan->lock, flags);
+ was_enabled = nco_is_enabled(hw);
+ nco_disable_nolock(hw);
+
+ writel_relaxed(div, chan->base + REG_DIV);
+ writel_relaxed(inc1, chan->base + REG_INC1);
+ writel_relaxed(inc2, chan->base + REG_INC2);
+
+ /* Presumably a neutral initial value for accumulator */
+ writel_relaxed(1 << 31, chan->base + REG_ACCINIT);
+
+ if (was_enabled)
+ nco_enable_nolock(hw);
+ spin_unlock_irqrestore(&chan->lock, flags);
+
+ return 0;
+}
+
+static unsigned long nco_recalc_rate(struct clk_hw *hw,
+ unsigned long parent_rate)
+{
+ struct nco_channel *chan = to_nco_channel(hw);
+ u32 div;
+ s32 inc1, inc2, incbase;
+
+ div = nco_div_translate_inv(chan->tbl,
+ readl_relaxed(chan->base + REG_DIV));
+
+ inc1 = readl_relaxed(chan->base + REG_INC1);
+ inc2 = readl_relaxed(chan->base + REG_INC2);
+
+ /*
+ * We don't support wraparound of accumulator
+ * nor the edge case of both increments being zero
+ */
+ if (inc1 < 0 || inc2 > 0 || (inc1 == 0 && inc2 == 0))
+ return 0;
+
+ /* Scale both sides of division by incbase to maintain precision */
+ incbase = inc1 - inc2;
+
+ return div_u64(((u64) parent_rate) * 2 * incbase,
+ ((u64) div) * incbase + inc1);
+}
+
+static long nco_round_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long *parent_rate)
+{
+ unsigned long lo = *parent_rate / (COARSE_DIV_OFFSET + LFSR_TBLSIZE) + 1;
+ unsigned long hi = *parent_rate / COARSE_DIV_OFFSET;
+
+ return clamp(rate, lo, hi);
+}
+
+static void nco_enable_nolock(struct clk_hw *hw)
+{
+ struct nco_channel *chan = to_nco_channel(hw);
+ u32 val;
+
+ val = readl_relaxed(chan->base + REG_CTRL);
+ writel_relaxed(val | CTRL_ENABLE, chan->base + REG_CTRL);
+}
+
+static void nco_disable_nolock(struct clk_hw *hw)
+{
+ struct nco_channel *chan = to_nco_channel(hw);
+ u32 val;
+
+ val = readl_relaxed(chan->base + REG_CTRL);
+ writel_relaxed(val & ~CTRL_ENABLE, chan->base + REG_CTRL);
+}
+
+static int nco_is_enabled(struct clk_hw *hw)
+{
+ struct nco_channel *chan = to_nco_channel(hw);
+
+ return (readl_relaxed(chan->base + REG_CTRL) & CTRL_ENABLE) != 0;
+}
+
+static int nco_enable(struct clk_hw *hw)
+{
+ struct nco_channel *chan = to_nco_channel(hw);
+ unsigned long flags;
+
+ spin_lock_irqsave(&chan->lock, flags);
+ nco_enable_nolock(hw);
+ spin_unlock_irqrestore(&chan->lock, flags);
+
+ return 0;
+}
+
+static void nco_disable(struct clk_hw *hw)
+{
+ struct nco_channel *chan = to_nco_channel(hw);
+ unsigned long flags;
+
+ spin_lock_irqsave(&chan->lock, flags);
+ nco_disable_nolock(hw);
+ spin_unlock_irqrestore(&chan->lock, flags);
+}
+
+static const struct clk_ops nco_ops = {
+ .set_rate = nco_set_rate,
+ .recalc_rate = nco_recalc_rate,
+ .round_rate = nco_round_rate,
+ .enable = nco_enable,
+ .disable = nco_disable,
+ .is_enabled = nco_is_enabled,
+};
+
+static int apple_nco_probe(struct platform_device *pdev)
+{
+ struct device_node *np = pdev->dev.of_node;
+ struct clk_parent_data pdata = { .index = 0 };
+ struct clk_init_data init;
+ struct clk_hw_onecell_data *onecell_data;
+ void __iomem *regs;
+ struct resource *regs_res;
+ struct nco_tables *tbl;
+ unsigned int nchannels;
+ int ret, i;
+
+ regs = devm_platform_get_and_ioremap_resource(pdev, 0, ®s_res);
+ if (IS_ERR(regs))
+ return PTR_ERR(regs);
+
+ if (resource_size(regs_res) < NCO_CHANNEL_REGSIZE)
+ return -EINVAL;
+ nchannels = (resource_size(regs_res) - NCO_CHANNEL_REGSIZE)
+ / NCO_CHANNEL_STRIDE + 1;
+
+ onecell_data = devm_kzalloc(&pdev->dev, struct_size(onecell_data, hws,
+ nchannels), GFP_KERNEL);
+ if (!onecell_data)
+ return -ENOMEM;
+ onecell_data->num = nchannels;
+
+ tbl = devm_kzalloc(&pdev->dev, sizeof(*tbl), GFP_KERNEL);
+ if (!tbl)
+ return -ENOMEM;
+ nco_compute_tables(tbl);
+
+ for (i = 0; i < nchannels; i++) {
+ struct nco_channel *chan;
+
+ chan = devm_kzalloc(&pdev->dev, sizeof(*chan), GFP_KERNEL);
+ if (!chan)
+ return -ENOMEM;
+ chan->base = regs + NCO_CHANNEL_STRIDE*i;
+ chan->tbl = tbl;
+ spin_lock_init(&chan->lock);
+
+ memset(&init, 0, sizeof(init));
+ init.name = devm_kasprintf(&pdev->dev, GFP_KERNEL,
+ "%s-%d", np->name, i);
+ init.ops = &nco_ops;
+ init.parent_data = &pdata;
+ init.num_parents = 1;
+ init.flags = 0;
+
+ chan->hw.init = &init;
+ ret = devm_clk_hw_register(&pdev->dev, &chan->hw);
+ if (ret)
+ return ret;
+
+ onecell_data->hws[i] = &chan->hw;
+ }
+
+ return devm_of_clk_add_hw_provider(&pdev->dev, of_clk_hw_onecell_get,
+ onecell_data);
+}
+
+static const struct of_device_id apple_nco_ids[] = {
+ { .compatible = "apple,nco" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, apple_nco_ids)
+
+static struct platform_driver apple_nco_driver = {
+ .driver = {
+ .name = "apple-nco",
+ .of_match_table = apple_nco_ids,
+ },
+ .probe = apple_nco_probe,
+};
+module_platform_driver(apple_nco_driver);
+
+MODULE_AUTHOR("Martin Povišer <povik+lin@xxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Clock driver for NCO blocks on Apple SoCs");
+MODULE_LICENSE("GPL v2");
--
2.33.0
