linux-kernel - Re: [PATCH 1/4] arm: pxa: change clocks init sequence

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Date:	Mon, 12 Jan 2015 15:48:20 -0800
From:	Mike Turquette <mturquette@...aro.org>
To:	Robert Jarzmik <robert.jarzmik@...e.fr>,
	"Daniel Mack" <daniel@...que.org>,
	"Haojian Zhuang" <haojian.zhuang@...il.com>,
	"Robert Jarzmik" <robert.jarzmik@...e.fr>,
	"Stephen Boyd" <sboyd@...eaurora.org>,
	"Laurent Pinchart" <laurent.pinchart@...asonboard.com>,
	"Dmitry Eremin-Solenikov" <dbaryshkov@...il.com>,
	"Arnd Bergmann" <arnd@...db.de>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] arm: pxa: change clocks init sequence

Quoting Robert Jarzmik (2014-12-27 05:55:25)
> Since pxa clocks were ported to the clock framework, an ordering issue
> appears between clocks and clocksource initialization. As a consequence,
> the pxa timer clock cannot be acquired in pxa_timer, and is disabled by
> clock framework because it is "unused".
> 
> The ordering issue is that in the kernel boot sequence :
>   start_kernel()
>     ...
>     time_init()
>       -> pxa_timer()
>         -> here the clocksource is initialized
>     ...
>     rest_init()
>       kernel_init()
>         initcalls
>           -> here the clocks are initialized
> 
> In the current sequence, the clocks are initialized way after pxa_timer,
> which cannot acquire the OSTIMER0 clock.
> 
> To solve this issue, the clocks initialization is moved to pxa_timer(),
> so that clocks are initialized before clocksource for non device-tree.
> For device-tree, the standard arm time_init() will take care of the
> ordering.
> 
> Signed-off-by: Robert Jarzmik <robert.jarzmik@...e.fr>

Reviewed-by: Michael Turquette <mturquette@...aro.org>

> ---
>  arch/arm/mach-pxa/generic.c  | 4 ++++
>  arch/arm/mach-pxa/generic.h  | 2 ++
>  drivers/clk/pxa/clk-pxa27x.c | 3 +--
>  3 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/mach-pxa/generic.c b/arch/arm/mach-pxa/generic.c
> index 04b013f..d988c53 100644
> --- a/arch/arm/mach-pxa/generic.c
> +++ b/arch/arm/mach-pxa/generic.c
> @@ -63,6 +63,10 @@ EXPORT_SYMBOL(get_clock_tick_rate);
>   */
>  void __init pxa_timer_init(void)
>  {
> +       if (cpu_is_pxa25x())
> +               pxa25x_clocks_init();
> +       if (cpu_is_pxa27x())
> +               pxa27x_clocks_init();
>         pxa_timer_nodt_init(IRQ_OST0, io_p2v(0x40a00000),
>                             get_clock_tick_rate());
>  }
> diff --git a/arch/arm/mach-pxa/generic.h b/arch/arm/mach-pxa/generic.h
> index 7a9fa1a..149087c 100644
> --- a/arch/arm/mach-pxa/generic.h
> +++ b/arch/arm/mach-pxa/generic.h
> @@ -26,11 +26,13 @@ extern void pxa_timer_init(void);
>  #define ARRAY_AND_SIZE(x)      (x), ARRAY_SIZE(x)
>  
>  #define pxa25x_handle_irq icip_handle_irq
> +extern int __init pxa25x_clocks_init(void);
>  extern void __init pxa25x_init_irq(void);
>  extern void __init pxa25x_map_io(void);
>  extern void __init pxa26x_init_irq(void);
>  
>  #define pxa27x_handle_irq ichp_handle_irq
> +extern int __init pxa27x_clocks_init(void);
>  extern void __init pxa27x_dt_init_irq(void);
>  extern unsigned        pxa27x_get_clk_frequency_khz(int);
>  extern void __init pxa27x_init_irq(void);
> diff --git a/drivers/clk/pxa/clk-pxa27x.c b/drivers/clk/pxa/clk-pxa27x.c
> index 5f9b54b..2b8343a 100644
> --- a/drivers/clk/pxa/clk-pxa27x.c
> +++ b/drivers/clk/pxa/clk-pxa27x.c
> @@ -362,12 +362,11 @@ static void __init pxa27x_base_clocks_init(void)
>         clk_register_clk_pxa27x_lcd_base();
>  }
>  
> -static int __init pxa27x_clocks_init(void)
> +int __init pxa27x_clocks_init(void)
>  {
>         pxa27x_base_clocks_init();
>         return clk_pxa_cken_init(pxa27x_clocks, ARRAY_SIZE(pxa27x_clocks));
>  }
> -postcore_initcall(pxa27x_clocks_init);
>  
>  static void __init pxa27x_dt_clocks_init(struct device_node *np)
>  {
> -- 
> 2.1.0
> 
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