arm: imx: correct the hardware clock gate setting for shared nodes

For those clk gates which hold share count, since its is_enabled callback is only checking the share count rather than reading the hardware register setting, in the late phase of kernel bootup, the clk_disable_unused action will NOT handle the scenario of share_count is 0 but the hardware setting is enabled, actually, U-Boot normally enables all clk gates, then those shared clk gates will be always enabled until they are used by some modules.

So the problem would be: when kernel boot up, the usecount cat from clk tree is 0, but the clk gates actually is enabled in hardware register, it will confuse user and bring unnecessary power consumption.

This patch adds .disable_unused callback and using hardware register check for .is_enabled callback of shared nodes to handle such scenario in late phase of kernel boot up, then the hardware status will match the clk tree info.

Signed-off-by Anson Huang <[email protected]>

---
changes from V2:
1. uboot -> U-Boot;
2. add .is_enabled change into commit log;
3. improve the condition check code.

 arch/arm/mach-imx/clk-gate2.c |   23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

arch/arm/mach-imx/clk-gate2.c +2 -4

index 5a75cdc..8935bff 100644
@@ -96,15 +96,30 @@ static int clk_gate2_is_enabled(struct clk_hw *hw)
 {
 	struct clk_gate2 *gate = to_clk_gate2(hw);
 
-	if (gate->share_count)
-		return !!__clk_get_enable_count(hw->clk);
-	else
-		return clk_gate2_reg_is_enabled(gate->reg, gate->bit_idx);
+	return clk_gate2_reg_is_enabled(gate->reg, gate->bit_idx);
+}

arch/arm/mach-imx/clk-gate2.c +4 -0

+		reg = readl(gate->reg);
+		reg &= ~(3 << gate->bit_idx);
+		writel(reg, gate->reg);
+	}

Quoted 7 lines · Anson Huang

For those clk gates which hold share count, since its is_enabled callback is only checking the share count rather than reading the hardware register setting, in the late phase of kernel bootup, the clk_disable_unused action will NOT handle the scenario of share_count is 0 but the hardware setting is enabled, actually, U-Boot normally enables all clk gates, then those shared clk gates will be always enabled until they are used by some modules.

Wow, this is one long sentence! :-) Could you split that up and simplify it a bit? Especially the "hold share count" part confused me at first, I thought you mean *share_count > 0, but you actually ment share_count != NULL (maybe "clk gates which have share count allocated").

Quoted 41 lines

So the problem would be: when kernel boot up, the usecount cat from clk tree is 0, but the clk gates actually is enabled in hardware register, it will confuse user and bring unnecessary power consumption.

This patch adds .disable_unused callback and using hardware register check for .is_enabled callback of shared nodes to handle such scenario in late phase of kernel boot up, then the hardware status will match the clk tree info.

Signed-off-by Anson Huang <[email protected]>

---
changes from V2:
1. uboot -> U-Boot;
2. add .is_enabled change into commit log;
3. improve the condition check code.

 arch/arm/mach-imx/clk-gate2.c |   23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

arch/arm/mach-imx/clk-gate2.c +9 -4

index 5a75cdc..8935bff 100644
@@ -96,15 +96,30 @@ static int clk_gate2_is_enabled(struct clk_hw *hw)
 {
 	struct clk_gate2 *gate = to_clk_gate2(hw);
 
-	if (gate->share_count)
-		return !!__clk_get_enable_count(hw->clk);
-	else
-		return clk_gate2_reg_is_enabled(gate->reg, gate->bit_idx);
+	return clk_gate2_reg_is_enabled(gate->reg, gate->bit_idx);
+}
+
+static void clk_gate2_disable_unused(struct clk_hw *hw)
+{
+	struct clk_gate2 *gate = to_clk_gate2(hw);
+	unsigned long flags = 0;
+	u32 reg;
+

arch/arm/mach-imx/clk-gate2.c static int clk_gate2_is_enabled(struct clk_hw *hw) · line 110

Quoted 3 lines

arch/arm/mach-imx/clk-gate2.c +3 -0

+	spin_lock_irqsave(gate->lock, flags);
+
+	if (!gate->share_count || *gate->share_count == 0) {

By introducing the .disable_unused callback the framework won't call the .disable callback anymore, even if enable_count is 0 and the clock is enabled according to .is_enabled. Wouldn't this interfere the disabling of normal, non-shared clock gates?

Quoted 4 lines

arch/arm/mach-imx/clk-gate2.c +4 -0

+		reg = readl(gate->reg);
+		reg &= ~(3 << gate->bit_idx);
+		writel(reg, gate->reg);
+	}

arch/arm/mach-imx/clk-gate2.c static int clk_gate2_is_enabled(struct clk_hw *hw) · line 124

Quoted 10 lines

arch/arm/mach-imx/clk-gate2.c +3 -0

+
+	spin_unlock_irqrestore(gate->lock, flags);
 }
 
 static struct clk_ops clk_gate2_ops = {
 	.enable = clk_gate2_enable,
 	.disable = clk_gate2_disable,
+	.disable_unused = clk_gate2_disable_unused,
 	.is_enabled = clk_gate2_is_enabled,
 };

--
Stefan

For those clk gates which hold share count, since its is_enabled callback is only checking the share count rather than reading the hardware register setting, in the late phase of kernel bootup, the clk_disable_unused action will NOT handle the scenario of share_count is 0 but the hardware setting is enabled, actually, U-Boot normally enables all clk gates, then those shared clk gates will be always enabled until they are used by some modules.

So the problem would be: when kernel boot up, the usecount cat from clk tree is 0, but the clk gates actually is enabled in hardware register, it will confuse user and bring unnecessary power consumption.

This patch adds .disable_unused callback and using hardware register check for .is_enabled callback of shared nodes to handle such scenario in late phase of kernel boot up, then the hardware status will match the clk tree info.

Signed-off-by Anson Huang <[email protected]>