[PATCH] clk: aspeed: Treat a gate in reset as disabled

[PATCH] clk: aspeed: Treat a gate in reset as disabled

[Benjamin Herrenschmidt]

On some systems, we come out of the bootloader with some
gates set with the clock "enabled" but the reset also
asserted.

Since 8a53fc511c5e "clk: aspeed: Prevent reset if clock is enabled"
we check that enabled bit in aspeed_clk_enabled(), and do
nothing if already set.

This breaks when the above scenario occurs, as the clock
is enabled, but the reset still needs to be lifted.

This patch fixes it by also checking the reset bit (if any)
and treating a gate in "reset" as being disabled.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Fixes: 8a53fc511c5e "clk: aspeed: Prevent reset if clock is enabled"
CC: Eddie James <eajames@linux.vnet.ibm.com>
---
 drivers/clk/clk-aspeed.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/clk/clk-aspeed.c b/drivers/clk/clk-aspeed.c
index c17032bc853a..c555eac2c528 100644
--- a/drivers/clk/clk-aspeed.c
+++ b/drivers/clk/clk-aspeed.c
@@ -212,9 +212,22 @@ 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 rst = BIT(gate->reset_idx);
 	u32 enval = (gate->flags & CLK_GATE_SET_TO_DISABLE) ? 0 : clk;
 	u32 reg;
 
+	/*
+	 * If the IP is in reset, treat the clock as not enabled,
+	 * this happens with some clocks such as the USB one when
+	 * coming from cold reset. Without this, aspeed_clk_enable()
+	 * will fail to lift the reset.
+	 */
+	if (gate->reset_idx >= 0) {
+		regmap_read(gate->map, ASPEED_RESET_CTRL, &reg);
+		if (reg & rst)
+			return 0;
+	}
+
 	regmap_read(gate->map, ASPEED_CLK_STOP_CTRL, &reg);
 
 	return ((reg & clk) == enval) ? 1 : 0;

Re: [PATCH] clk: aspeed: Treat a gate in reset as disabled

[Joel Stanley]

On 3 July 2018 at 17:24, Benjamin Herrenschmidt <benh@linux.vnet.ibm.com> wrote:
> On some systems, we come out of the bootloader with some
> gates set with the clock "enabled" but the reset also
> asserted.
>
> Since 8a53fc511c5e "clk: aspeed: Prevent reset if clock is enabled"
> we check that enabled bit in aspeed_clk_enabled(), and do
> nothing if already set.
>
> This breaks when the above scenario occurs, as the clock
> is enabled, but the reset still needs to be lifted.
>
> This patch fixes it by also checking the reset bit (if any)
> and treating a gate in "reset" as being disabled.
>
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Fixes: 8a53fc511c5e "clk: aspeed: Prevent reset if clock is enabled"
> CC: Eddie James <eajames@linux.vnet.ibm.com>

Reviewed-by: Joel Stanley <joel@jms.id.au>

Thanks Ben.

> ---
>  drivers/clk/clk-aspeed.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/drivers/clk/clk-aspeed.c b/drivers/clk/clk-aspeed.c
> index c17032bc853a..c555eac2c528 100644
> --- a/drivers/clk/clk-aspeed.c
> +++ b/drivers/clk/clk-aspeed.c
> @@ -212,9 +212,22 @@ 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 rst = BIT(gate->reset_idx);
>         u32 enval = (gate->flags & CLK_GATE_SET_TO_DISABLE) ? 0 : clk;
>         u32 reg;
>
> +       /*
> +        * If the IP is in reset, treat the clock as not enabled,
> +        * this happens with some clocks such as the USB one when
> +        * coming from cold reset. Without this, aspeed_clk_enable()
> +        * will fail to lift the reset.
> +        */
> +       if (gate->reset_idx >= 0) {
> +               regmap_read(gate->map, ASPEED_RESET_CTRL, &reg);
> +               if (reg & rst)
> +                       return 0;
> +       }
> +
>         regmap_read(gate->map, ASPEED_CLK_STOP_CTRL, &reg);
>
>         return ((reg & clk) == enval) ? 1 : 0;
>

Re: [PATCH] clk: aspeed: Treat a gate in reset as disabled

[Stephen Boyd]

Quoting Benjamin Herrenschmidt (2018-07-03 00:24:47)
> On some systems, we come out of the bootloader with some
> gates set with the clock "enabled" but the reset also
> asserted.
> =

> Since 8a53fc511c5e "clk: aspeed: Prevent reset if clock is enabled"
> we check that enabled bit in aspeed_clk_enabled(), and do
> nothing if already set.
> =

> This breaks when the above scenario occurs, as the clock
> is enabled, but the reset still needs to be lifted.
> =

> This patch fixes it by also checking the reset bit (if any)
> and treating a gate in "reset" as being disabled.
> =

> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Fixes: 8a53fc511c5e "clk: aspeed: Prevent reset if clock is enabled"
> CC: Eddie James <eajames@linux.vnet.ibm.com>
> ---

Applied to clk-fixes