Re: [PATCH] clk: ti: Fix FAPLL udelay in clk_enable with clk_prepare

[Peter Ujfalusi <peter.ujfalusi@ti.com>]

Tony,

On 09/23/2015 12:23 AM, Tony Lindgren wrote:
> As recently pointed out (again) by Thomas and Russell, we must not
> wait in in clk_enable. The wait for PLL to lock needs to happen
> in clk_prepare instead.
> 
> It seems this is a common copy paste error with the PLL drivers,
> and similar fixes should be applied to other PLL drivers after
> testing.

One thing to note:
because of how the hwmod code works, at boot time we prepare all clocks for
the devices and in runtime the hwmod only uses clk_enable/disable, it will
never unprepare the clock(s). This will means that these clocks will be
enabled all the time and will never turned off.

-- 
Péter

> Cc: Brian Hutchinson <b.hutchman@gmail.com>
> Cc: Felipe Balbi <balbi@ti.com>
> Cc: Grygorii Strashko <grygorii.strashko@ti.com>
> Cc: Nishanth Menon <nm@ti.com>
> Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Sekhar Nori <nsekhar@ti.com>
> Signed-off-by: Tony Lindgren <tony@atomide.com>
> ---
>  drivers/clk/ti/fapll.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/clk/ti/fapll.c b/drivers/clk/ti/fapll.c
> index f4b2e98..e1db74a 100644
> --- a/drivers/clk/ti/fapll.c
> +++ b/drivers/clk/ti/fapll.c
> @@ -37,7 +37,7 @@
>  #define FAPLL_PWD_OFFSET	4
>  
>  #define MAX_FAPLL_OUTPUTS	7
> -#define FAPLL_MAX_RETRIES	1000
> +#define FAPLL_MAX_RETRIES	5
>  
>  #define to_fapll(_hw)		container_of(_hw, struct fapll_data, hw)
>  #define to_synth(_hw)		container_of(_hw, struct fapll_synth, hw)
> @@ -126,7 +126,7 @@ static int ti_fapll_wait_lock(struct fapll_data *fd)
>  		if (retries-- <= 0)
>  			break;
>  
> -		udelay(1);
> +		usleep_range(200, 300);
>  	}
>  
>  	pr_err("%s failed to lock\n", fd->name);
> @@ -134,7 +134,7 @@ static int ti_fapll_wait_lock(struct fapll_data *fd)
>  	return -ETIMEDOUT;
>  }
>  
> -static int ti_fapll_enable(struct clk_hw *hw)
> +static int ti_fapll_prepare(struct clk_hw *hw)
>  {
>  	struct fapll_data *fd = to_fapll(hw);
>  	u32 v = readl_relaxed(fd->base);
> @@ -146,7 +146,7 @@ static int ti_fapll_enable(struct clk_hw *hw)
>  	return 0;
>  }
>  
> -static void ti_fapll_disable(struct clk_hw *hw)
> +static void ti_fapll_unprepare(struct clk_hw *hw)
>  {
>  	struct fapll_data *fd = to_fapll(hw);
>  	u32 v = readl_relaxed(fd->base);
> @@ -155,7 +155,7 @@ static void ti_fapll_disable(struct clk_hw *hw)
>  	writel_relaxed(v, fd->base);
>  }
>  
> -static int ti_fapll_is_enabled(struct clk_hw *hw)
> +static int ti_fapll_is_prepared(struct clk_hw *hw)
>  {
>  	struct fapll_data *fd = to_fapll(hw);
>  	u32 v = readl_relaxed(fd->base);
> @@ -261,7 +261,7 @@ static int ti_fapll_set_rate(struct clk_hw *hw, unsigned long rate,
>  	v |= pre_div_p << FAPLL_MAIN_DIV_P_SHIFT;
>  	v |= mult_n << FAPLL_MAIN_MULT_N_SHIFT;
>  	writel_relaxed(v, fd->base);
> -	if (ti_fapll_is_enabled(hw))
> +	if (ti_fapll_is_prepared(hw))
>  		ti_fapll_wait_lock(fd);
>  	ti_fapll_clear_bypass(fd);
>  
> @@ -269,9 +269,9 @@ static int ti_fapll_set_rate(struct clk_hw *hw, unsigned long rate,
>  }
>  
>  static struct clk_ops ti_fapll_ops = {
> -	.enable = ti_fapll_enable,
> -	.disable = ti_fapll_disable,
> -	.is_enabled = ti_fapll_is_enabled,
> +	.prepare = ti_fapll_prepare,
> +	.unprepare = ti_fapll_unprepare,
> +	.is_prepared = ti_fapll_is_prepared,
>  	.recalc_rate = ti_fapll_recalc_rate,
>  	.get_parent = ti_fapll_get_parent,
>  	.round_rate = ti_fapll_round_rate,
>