clk: ti: add custom API for memory access

As pointed by [1] and [2], commit
d64b9cdcd4 ("fdt: translate address if #size-cells = <0>") is wrong:
- It makes every 'reg' DT property translatable. It changes the address
  translation so that for an I2C 'reg' address you'll get back as reg
  the I2C controller address + reg value.
- The quirk must be fixed with platform code.

The clk_ti_get_reg_addr() is the platform code able to make the correct
address translation for the AM33xx clocks registers. Its implementation
was inspired by the Linux Kernel code.

[1] https://patchwork.ozlabs.org/project/uboot/patch/1614324949-61314-1-git-send-email-bmeng.cn@gmail.com/
[2] https://lore.kernel.org/linux-clk/20210402192054.7934-1-dariobin@libero.it/T/

Signed-off-by: Dario Binacchi <dariobin@libero.it>

drivers/clk/ti/clk.c

@@ -6,10 +6,23 @@
  */
 
 #include <common.h>
+#include <dm.h>
 #include <fdtdec.h>
+#include <regmap.h>
 #include <asm/io.h>
+#include <dm/device_compat.h>
 #include "clk.h"
 
+#define CLK_MAX_MEMMAPS           10
+
+struct clk_iomap {
+	struct regmap *regmap;
+	ofnode node;
+};
+
+static unsigned int clk_memmaps_num;
+static struct clk_iomap clk_memmaps[CLK_MAX_MEMMAPS];
+
 static void clk_ti_rmw(u32 val, u32 mask, fdt_addr_t reg)
 {
 	u32 v;
@@ -33,3 +46,75 @@ void clk_ti_latch(fdt_addr_t reg, s8 shift)
 	clk_ti_rmw(0, latch, reg);
 	readl(reg);		/* OCP barrier */
 }
+
+void clk_ti_writel(u32 val, struct clk_ti_reg *reg)
+{
+	struct clk_iomap *io = &clk_memmaps[reg->index];
+
+	regmap_write(io->regmap, reg->offset, val);
+}
+
+u32 clk_ti_readl(struct clk_ti_reg *reg)
+{
+	struct clk_iomap *io = &clk_memmaps[reg->index];
+	u32 val;
+
+	regmap_read(io->regmap, reg->offset, &val);
+	return val;
+}
+
+static ofnode clk_ti_get_regmap_node(struct udevice *dev)
+{
+	ofnode node = dev_ofnode(dev), parent;
+
+	if (!ofnode_valid(node))
+		return ofnode_null();
+
+	parent = ofnode_get_parent(node);
+	if (strcmp(ofnode_get_name(parent), "clocks"))
+		return ofnode_null();
+
+	return ofnode_get_parent(parent);
+}
+
+int clk_ti_get_reg_addr(struct udevice *dev, int index, struct clk_ti_reg *reg)
+{
+	ofnode node;
+	int i, ret;
+	u32 val;
+
+	ret = ofnode_read_u32_index(dev_ofnode(dev), "reg", index, &val);
+	if (ret) {
+		dev_err(dev, "%s must have reg[%d]\n", ofnode_get_name(node),
+			index);
+		return ret;
+	}
+
+	/* parent = ofnode_get_parent(parent); */
+	node = clk_ti_get_regmap_node(dev);
+	if (!ofnode_valid(node)) {
+		dev_err(dev, "failed to get regmap node\n");
+		return -EFAULT;
+	}
+
+	for (i = 0; i < clk_memmaps_num; i++) {
+		if (ofnode_equal(clk_memmaps[i].node, node))
+			break;
+	}
+
+	if (i == clk_memmaps_num) {
+		if (i == CLK_MAX_MEMMAPS)
+			return -ENOMEM;
+
+		ret = regmap_init_mem(node, &clk_memmaps[i].regmap);
+		if (ret)
+			return ret;
+
+		clk_memmaps[i].node = node;
+		clk_memmaps_num++;
+	}
+
+	reg->index = i;
+	reg->offset = val;
+	return 0;
+}

drivers/clk/ti/clk.h

@@ -9,5 +9,18 @@
 #define _CLK_TI_H
 
 void clk_ti_latch(fdt_addr_t reg, s8 shift);
+/**
+ * struct clk_ti_reg - TI register declaration
+ * @offset: offset from the master IP module base address
+ * @index: index of the master IP module
+ */
+struct clk_ti_reg {
+	u16 offset;
+	u8 index;
+};
+
+void clk_ti_writel(u32 val, struct clk_ti_reg *reg);
+u32 clk_ti_readl(struct clk_ti_reg *reg);
+int clk_ti_get_reg_addr(struct udevice *dev, int index, struct clk_ti_reg *reg);
 
 #endif /* #ifndef _CLK_TI_H */