clk: divider: read-only divider can propagate rate change

When a divider clock has CLK_DIVIDER_READ_ONLY set, it means that the
register shall be left un-touched, but it does not mean the clock
should stop rate propagation if CLK_SET_RATE_PARENT is set

This is properly handled in qcom clk-regmap-divider but it was not in
the generic divider

To fix this situation, introduce a new helper function
divider_ro_round_rate, on the same model as divider_round_rate.

Fixes: e6d5e7d90be9 ("clk-divider: Fix READ_ONLY when divider > 1")
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Tested-By: David Lechner <david@lechnology.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

2 files changed, 45 insertions, 6 deletions

diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index 3c98d2650fa3..b6234a5da12d 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -342,19 +342,43 @@ long divider_round_rate_parent(struct clk_hw *hw, struct clk_hw *parent,
 }
 EXPORT_SYMBOL_GPL(divider_round_rate_parent);
 
+long divider_ro_round_rate_parent(struct clk_hw *hw, struct clk_hw *parent,
+                                  unsigned long rate, unsigned long *prate,
+                                  const struct clk_div_table *table, u8 width,
+                                  unsigned long flags, unsigned int val)
+{
+        int div;
+
+        div = _get_div(table, val, flags, width);
+
+        /* Even a read-only clock can propagate a rate change */
+        if (clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT) {
+                if (!parent)
+                        return -EINVAL;
+
+                *prate = clk_hw_round_rate(parent, rate * div);
+        }
+
+        return DIV_ROUND_UP_ULL((u64)*prate, div);
+}
+EXPORT_SYMBOL_GPL(divider_ro_round_rate_parent);
+
+
 static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
                                 unsigned long *prate)
 {
         struct clk_divider *divider = to_clk_divider(hw);
-        int bestdiv;
 
         /* if read only, just return current value */
         if (divider->flags & CLK_DIVIDER_READ_ONLY) {
-                bestdiv = clk_readl(divider->reg) >> divider->shift;
-                bestdiv &= clk_div_mask(divider->width);
-                bestdiv = _get_div(divider->table, bestdiv, divider->flags,
-                        divider->width);
-                return DIV_ROUND_UP_ULL((u64)*prate, bestdiv);
+                u32 val;
+
+                val = clk_readl(divider->reg) >> divider->shift;
+                val &= clk_div_mask(divider->width);
+
+                return divider_ro_round_rate(hw, rate, prate, divider->table,
+                                             divider->width, divider->flags,
+                                             val);
         }
 
         return divider_round_rate(hw, rate, prate, divider->table,
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index cb18526d69cb..210a890008f9 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -420,6 +420,10 @@ long divider_round_rate_parent(struct clk_hw *hw, struct clk_hw *parent,
                                unsigned long rate, unsigned long *prate,
                                const struct clk_div_table *table,
                                u8 width, unsigned long flags);
+long divider_ro_round_rate_parent(struct clk_hw *hw, struct clk_hw *parent,
+                                  unsigned long rate, unsigned long *prate,
+                                  const struct clk_div_table *table, u8 width,
+                                  unsigned long flags, unsigned int val);
 int divider_get_val(unsigned long rate, unsigned long parent_rate,
                 const struct clk_div_table *table, u8 width,
                 unsigned long flags);
@@ -780,6 +784,17 @@ static inline long divider_round_rate(struct clk_hw *hw, unsigned long rate,
                                          rate, prate, table, width, flags);
 }
 
+static inline long divider_ro_round_rate(struct clk_hw *hw, unsigned long rate,
+                                         unsigned long *prate,
+                                         const struct clk_div_table *table,
+                                         u8 width, unsigned long flags,
+                                         unsigned int val)
+{
+        return divider_ro_round_rate_parent(hw, clk_hw_get_parent(hw),
+                                            rate, prate, table, width, flags,
+                                            val);
+}
+
 /*
  * FIXME clock api without lock protection
  */