clk: mux: add CLK_MUX_HIWORD_MASK

In both Hisilicon & Rockchip Cortex-A9 based chips, they don't use the
paradigm of reading-changing-writing the register contents.
Instead they use a hiword mask to indicate the changed bits.

When b01 should be set as switching mux, it also needs to indicate
the change by setting hiword mask (b11 << 16).

The patch adds mux flag for this usage.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

drivers/clk/clk-mux.c

@@ -86,8 +86,12 @@ static int clk_mux_set_parent(struct clk_hw *hw, u8 index)
 	if (mux->lock)
 		spin_lock_irqsave(mux->lock, flags);
 
-	val = readl(mux->reg);
-	val &= ~(mux->mask << mux->shift);
+	if (mux->flags & CLK_MUX_HIWORD_MASK) {
+		val = mux->mask << (mux->shift + 16);
+	} else {
+		val = readl(mux->reg);
+		val &= ~(mux->mask << mux->shift);
+	}
 	val |= index << mux->shift;
 	writel(val, mux->reg);
 
@@ -111,6 +115,15 @@ struct clk *clk_register_mux_table(struct device *dev, const char *name,
 	struct clk_mux *mux;
 	struct clk *clk;
 	struct clk_init_data init;
+	u8 width = 0;
+
+	if (clk_mux_flags & CLK_MUX_HIWORD_MASK) {
+		width = fls(mask) - ffs(mask) + 1;
+		if (width + shift > 16) {
+			pr_err("mux value exceeds LOWORD field\n");
+			return ERR_PTR(-EINVAL);
+		}
+	}
 
 	/* allocate the mux */
 	mux = kzalloc(sizeof(struct clk_mux), GFP_KERNEL);

include/linux/clk-provider.h

@@ -299,6 +299,10 @@ struct clk *clk_register_divider_table(struct device *dev, const char *name,
  * Flags:
  * CLK_MUX_INDEX_ONE - register index starts at 1, not 0
  * CLK_MUX_INDEX_BIT - register index is a single bit (power of two)
+ * CLK_MUX_HIWORD_MASK - The mux settings are only in lower 16-bit of this
+ *   register, and mask of mux bits are in higher 16-bit of this register.
+ *   While setting the mux bits, higher 16-bit should also be updated to
+ *   indicate changing mux bits.
  */
 struct clk_mux {
 	struct clk_hw	hw;
@@ -312,6 +316,7 @@ struct clk_mux {
 
 #define CLK_MUX_INDEX_ONE		BIT(0)
 #define CLK_MUX_INDEX_BIT		BIT(1)
+#define CLK_MUX_HIWORD_MASK		BIT(2)
 
 extern const struct clk_ops clk_mux_ops;