clk: aspeed: Prevent reset if clock is enabled

According to the Aspeed specification, the reset and enable sequence
should be done when the clock is stopped. The specification doesn't
define behavior if the reset is done while the clock is enabled.

From testing on the AST2500, the LPC Controller has problems if the
clock is reset while enabled.

Therefore, check whether the clock is enabled or not before performing
the reset and enable sequence in the Aspeed clock driver.

Reported-by: Lei Yu <mine260309@gmail.com>
Signed-off-by: Eddie James <eajames@linux.vnet.ibm.com>
Fixes: 15ed8ce5f84e ("clk: aspeed: Register gated clocks")
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

1 files changed, 17 insertions, 12 deletions

diff --git a/drivers/clk/clk-aspeed.c b/drivers/clk/clk-aspeed.c
index 168777175cd1..5eb50c31e455 100644
--- a/drivers/clk/clk-aspeed.c
+++ b/drivers/clk/clk-aspeed.c
@@ -205,6 +205,18 @@ static const struct aspeed_clk_soc_data ast2400_data = {
         .calc_pll = aspeed_ast2400_calc_pll,
 };
 
+static int aspeed_clk_is_enabled(struct clk_hw *hw)
+{
+        struct aspeed_clk_gate *gate = to_aspeed_clk_gate(hw);
+        u32 clk = BIT(gate->clock_idx);
+        u32 enval = (gate->flags & CLK_GATE_SET_TO_DISABLE) ? 0 : clk;
+        u32 reg;
+
+        regmap_read(gate->map, ASPEED_CLK_STOP_CTRL, &reg);
+
+        return ((reg & clk) == enval) ? 1 : 0;
+}
+
 static int aspeed_clk_enable(struct clk_hw *hw)
 {
         struct aspeed_clk_gate *gate = to_aspeed_clk_gate(hw);
@@ -215,6 +227,11 @@ static int aspeed_clk_enable(struct clk_hw *hw)
 
         spin_lock_irqsave(gate->lock, flags);
 
+        if (aspeed_clk_is_enabled(hw)) {
+                spin_unlock_irqrestore(gate->lock, flags);
+                return 0;
+        }
+
         if (gate->reset_idx >= 0) {
                 /* Put IP in reset */
                 regmap_update_bits(gate->map, ASPEED_RESET_CTRL, rst, rst);
@@ -255,18 +272,6 @@ static void aspeed_clk_disable(struct clk_hw *hw)
         spin_unlock_irqrestore(gate->lock, flags);
 }
 
-static int aspeed_clk_is_enabled(struct clk_hw *hw)
-{
-        struct aspeed_clk_gate *gate = to_aspeed_clk_gate(hw);
-        u32 clk = BIT(gate->clock_idx);
-        u32 enval = (gate->flags & CLK_GATE_SET_TO_DISABLE) ? 0 : clk;
-        u32 reg;
-
-        regmap_read(gate->map, ASPEED_CLK_STOP_CTRL, &reg);
-
-        return ((reg & clk) == enval) ? 1 : 0;
-}
-
 static const struct clk_ops aspeed_clk_gate_ops = {
         .enable = aspeed_clk_enable,
         .disable = aspeed_clk_disable,