clk: divider: add CLK_DIVIDER_HIWORD_MASK flag

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 setting divider, it also needs to indicate
the change by setting hiword mask (b11 << 16).

The patch adds divider 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>

2 files changed, 18 insertions, 2 deletions

diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index 6024e60e49aa..6d55eb2cb959 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -227,8 +227,12 @@ static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
         if (divider->lock)
                 spin_lock_irqsave(divider->lock, flags);
 
-        val = readl(divider->reg);
-        val &= ~(div_mask(divider) << divider->shift);
+        if (divider->flags & CLK_DIVIDER_HIWORD_MASK) {
+                val = div_mask(divider) << (divider->shift + 16);
+        } else {
+                val = readl(divider->reg);
+                val &= ~(div_mask(divider) << divider->shift);
+        }
         val |= value << divider->shift;
         writel(val, divider->reg);
 
@@ -255,6 +259,13 @@ static struct clk *_register_divider(struct device *dev, const char *name,
         struct clk *clk;
         struct clk_init_data init;
 
+        if (clk_divider_flags & CLK_DIVIDER_HIWORD_MASK) {
+                if (width + shift > 16) {
+                        pr_warn("divider value exceeds LOWORD field\n");
+                        return ERR_PTR(-EINVAL);
+                }
+        }
+
         /* allocate the divider */
         div = kzalloc(sizeof(struct clk_divider), GFP_KERNEL);
         if (!div) {
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 37ad97961e5a..d77f1267f419 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -257,6 +257,10 @@ struct clk_div_table {
  *      Some hardware implementations gracefully handle this case and allow a
  *      zero divisor by not modifying their input clock
  *      (divide by one / bypass).
+ * CLK_DIVIDER_HIWORD_MASK - The divider settings are only in lower 16-bit
+ *   of this register, and mask of divider bits are in higher 16-bit of this
+ *   register.  While setting the divider bits, higher 16-bit should also be
+ *   updated to indicate changing divider bits.
  */
 struct clk_divider {
         struct clk_hw   hw;
@@ -271,6 +275,7 @@ struct clk_divider {
 #define CLK_DIVIDER_ONE_BASED           BIT(0)
 #define CLK_DIVIDER_POWER_OF_TWO        BIT(1)
 #define CLK_DIVIDER_ALLOW_ZERO          BIT(2)
+#define CLK_DIVIDER_HIWORD_MASK         BIT(3)
 
 extern const struct clk_ops clk_divider_ops;
 struct clk *clk_register_divider(struct device *dev, const char *name,