clk: mmp2: Add support for PLL clock sources

The clk-of-mmp2 driver pretends that the clock outputs from the PLLs are
constant, but in fact they are configurable.

Add logic for obtaining the actual clock rates on MMP2 as well as MMP3.
There is no documentation for either SoC, but the "systemsetting" drivers
from Marvell GPL code dump provide some clue as far as MPMU registers on
MMP2 [1] and MMP3 [2] go.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/lkundrak/linux-mmp3-dell-ariel.git/tree/drivers/char/mmp2_systemsetting.c
[2] https://git.kernel.org/pub/scm/linux/kernel/git/lkundrak/linux-mmp3-dell-ariel.git/tree/drivers/char/mmp3_systemsetting.c

A separate commit will adjust the clk-of-mmp2 driver.

Tested on a MMP3-based Dell Wyse 3020 as well as MMP2-based OLPC
XO-1.75 laptop.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Link: https://lkml.kernel.org/r/20200309194254.29009-5-lkundrak@v3.sk
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

1 files changed, 139 insertions, 0 deletions

diff --git a/drivers/clk/mmp/clk-pll.c b/drivers/clk/mmp/clk-pll.c
new file mode 100644
index 000000000000..7077be293871
--- /dev/null
+++ b/drivers/clk/mmp/clk-pll.c
@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * MMP PLL clock rate calculation
+ *
+ * Copyright (C) 2020 Lubomir Rintel <lkundrak@v3.sk>
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+
+#include "clk.h"
+
+#define to_clk_mmp_pll(hw)	container_of(hw, struct mmp_clk_pll, hw)
+
+struct mmp_clk_pll {
+	struct clk_hw hw;
+	unsigned long default_rate;
+	void __iomem *enable_reg;
+	u32 enable;
+	void __iomem *reg;
+	u8 shift;
+
+	unsigned long input_rate;
+	void __iomem *postdiv_reg;
+	u8 postdiv_shift;
+};
+
+static int mmp_clk_pll_is_enabled(struct clk_hw *hw)
+{
+	struct mmp_clk_pll *pll = to_clk_mmp_pll(hw);
+	u32 val;
+
+	val = readl_relaxed(pll->enable_reg);
+	if ((val & pll->enable) == pll->enable)
+		return 1;
+
+	/* Some PLLs, if not software controlled, output default clock. */
+	if (pll->default_rate > 0)
+		return 1;
+
+	return 0;
+}
+
+static unsigned long mmp_clk_pll_recalc_rate(struct clk_hw *hw,
+					unsigned long parent_rate)
+{
+	struct mmp_clk_pll *pll = to_clk_mmp_pll(hw);
+	u32 fbdiv, refdiv, postdiv;
+	u64 rate;
+	u32 val;
+
+	val = readl_relaxed(pll->enable_reg);
+	if ((val & pll->enable) != pll->enable)
+		return pll->default_rate;
+
+	if (pll->reg) {
+		val = readl_relaxed(pll->reg);
+		fbdiv = (val >> pll->shift) & 0x1ff;
+		refdiv = (val >> (pll->shift + 9)) & 0x1f;
+	} else {
+		fbdiv = 2;
+		refdiv = 1;
+	}
+
+	if (pll->postdiv_reg) {
+		/* MMP3 clock rate calculation */
+		static const u8 postdivs[] = {2, 3, 4, 5, 6, 8, 10, 12, 16};
+
+		val = readl_relaxed(pll->postdiv_reg);
+		postdiv = (val >> pll->postdiv_shift) & 0x7;
+
+		rate = pll->input_rate;
+		rate *= 2 * fbdiv;
+		do_div(rate, refdiv);
+		do_div(rate, postdivs[postdiv]);
+	} else {
+		/* MMP2 clock rate calculation */
+		if (refdiv == 3) {
+			rate = 19200000;
+		} else if (refdiv == 4) {
+			rate = 26000000;
+		} else {
+			pr_err("bad refdiv: %d (0x%08x)\n", refdiv, val);
+			return 0;
+		}
+
+		rate *= fbdiv + 2;
+		do_div(rate, refdiv + 2);
+	}
+
+	return (unsigned long)rate;
+}
+
+static const struct clk_ops mmp_clk_pll_ops = {
+	.is_enabled = mmp_clk_pll_is_enabled,
+	.recalc_rate = mmp_clk_pll_recalc_rate,
+};
+
+struct clk *mmp_clk_register_pll(char *name,
+			unsigned long default_rate,
+			void __iomem *enable_reg, u32 enable,
+			void __iomem *reg, u8 shift,
+			unsigned long input_rate,
+			void __iomem *postdiv_reg, u8 postdiv_shift)
+{
+	struct mmp_clk_pll *pll;
+	struct clk *clk;
+	struct clk_init_data init;
+
+	pll = kzalloc(sizeof(*pll), GFP_KERNEL);
+	if (!pll)
+		return ERR_PTR(-ENOMEM);
+
+	init.name = name;
+	init.ops = &mmp_clk_pll_ops;
+	init.flags = 0;
+	init.parent_names = NULL;
+	init.num_parents = 0;
+
+	pll->default_rate = default_rate;
+	pll->enable_reg = enable_reg;
+	pll->enable = enable;
+	pll->reg = reg;
+	pll->shift = shift;
+
+	pll->input_rate = input_rate;
+	pll->postdiv_reg = postdiv_reg;
+	pll->postdiv_shift = postdiv_shift;
+
+	pll->hw.init = &init;
+
+	clk = clk_register(NULL, &pll->hw);
+
+	if (IS_ERR(clk))
+		kfree(pll);
+
+	return clk;
+}