[PATCH 00/20] ARM: at91: Properly handle slow clock

[PATCH 00/20] ARM: at91: Properly handle slow clock

[Alexandre Belloni]

Hi,

It was discovered that all the slow clock user were not properly claiming it.
This can end up in a system hang because the last registered user is releasing
it, and it gets disabled.

commit dca1a4b5ff6e ("clk: at91: keep slow clk enabled to prevent system hang")
was a workaround. This series is adding the slow clock to the necessary drivers
to avoid the issue and then removes that workaround.

The Documentation updates and DT patches should probably go through the AT91
tree this cycle to avoid breakage.

Then the other patches can go through each subsystem tree. They are trivial
enough to also go in this cycle.

The final clk patch depends on the other ones and may be taken for the next
cycle to avoid synchronization issues.

I've thrown in a cleanup for at91-reset as it avoids adding support for that
clock to the platform data initialization

Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: rtc-linux@googlegroups.com
Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: linux-watchdog@vger.kernel.org
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: linux-pm@vger.kernel.org
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: linux-clk@vger.kernel.org

Alexandre Belloni (20):
  Documentation: dt: atmel-at91: add clocks to system timer, rstc and
    shdwc
  Documentation: watchdog: at91sam9_wdt: add clocks property
  Documentation: dt: rtc: at91rm9200: add clocks property
  ARM: at91/dt: at91rm9200: use slow clock where necessary
  ARM: at91/dt: at91sam9260: use slow clock where necessary
  ARM: at91/dt: at91sam9261: use slow clock where necessary
  ARM: at91/dt: at91sam9263: use slow clock where necessary
  ARM: at91/dt: at91sam9g45: use slow clock where necessary
  ARM: at91/dt: at91sam9n12: use slow clock where necessary
  ARM: at91/dt: at91sam9rl: use slow clock where necessary
  ARM: at91/dt: at91sam9x5: use slow clock where necessary
  ARM: at91/dt: sama5d3: use slow clock where necessary
  ARM: at91/dt: sama5d4: use slow clock where necessary
  rtc: at91rm9200: get and use slow clock
  watchdog: at91sam9: get and use slow clock
  power/reset: at91-reset: remove useless at91_reset_platform_probe()
  power/reset: at91-reset: get and use slow clock
  power/reset: at91-poweroff: get and use slow clock
  clocksource: atmel-st: get and use slow clock
  clk: at91: Revert "keep slow clk enabled to prevent system hang"

 .../devicetree/bindings/arm/atmel-at91.txt         | 11 +++--
 .../bindings/rtc/atmel,at91rm9200-rtc.txt          |  2 +
 .../devicetree/bindings/watchdog/atmel-wdt.txt     |  2 +
 arch/arm/boot/dts/at91rm9200.dtsi                  |  2 +
 arch/arm/boot/dts/at91sam9260.dtsi                 |  3 ++
 arch/arm/boot/dts/at91sam9261.dtsi                 |  3 ++
 arch/arm/boot/dts/at91sam9263.dtsi                 |  3 ++
 arch/arm/boot/dts/at91sam9g45.dtsi                 |  4 ++
 arch/arm/boot/dts/at91sam9n12.dtsi                 |  4 ++
 arch/arm/boot/dts/at91sam9rl.dtsi                  |  4 ++
 arch/arm/boot/dts/at91sam9x5.dtsi                  |  4 ++
 arch/arm/boot/dts/sama5d3.dtsi                     |  4 ++
 arch/arm/boot/dts/sama5d4.dtsi                     |  4 ++
 drivers/clk/at91/clk-slow.c                        | 27 -------------
 drivers/clocksource/timer-atmel-st.c               | 31 +++++++++-----
 drivers/power/reset/at91-poweroff.c                | 13 ++++++
 drivers/power/reset/at91-reset.c                   | 47 ++++++----------------
 drivers/rtc/rtc-at91rm9200.c                       | 27 +++++++++++--
 drivers/watchdog/at91sam9_wdt.c                    | 22 +++++++++-
 19 files changed, 138 insertions(+), 79 deletions(-)

-- 
2.1.4


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[PATCH 20/20] clk: at91: Revert "keep slow clk enabled to prevent system hang"

[Alexandre Belloni]

Commit dca1a4b5ff6e ("clk: at91: keep slow clk enabled to prevent system
hang") added a workaround for the slow clock as it is not properly handled
by its users.

Now that the slow clock is taken properly by the drivers, this workaround
is not necessary anymore, revert it.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
---
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: linux-clk@vger.kernel.org
 drivers/clk/at91/clk-slow.c | 27 ---------------------------
 1 file changed, 27 deletions(-)

diff --git a/drivers/clk/at91/clk-slow.c b/drivers/clk/at91/clk-slow.c
index 98a84a865fe1..2c59d6a64dd5 100644
--- a/drivers/clk/at91/clk-slow.c
+++ b/drivers/clk/at91/clk-slow.c
@@ -70,7 +70,6 @@ struct clk_sam9x5_slow {
 
 #define to_clk_sam9x5_slow(hw) container_of(hw, struct clk_sam9x5_slow, hw)
 
-static struct clk *slow_clk;
 
 static int clk_slow_osc_prepare(struct clk_hw *hw)
 {
@@ -358,8 +357,6 @@ at91_clk_register_sam9x5_slow(void __iomem *sckcr,
 	clk = clk_register(NULL, &slowck->hw);
 	if (IS_ERR(clk))
 		kfree(slowck);
-	else
-		slow_clk = clk;
 
 	return clk;
 }
@@ -436,8 +433,6 @@ at91_clk_register_sam9260_slow(struct at91_pmc *pmc,
 	clk = clk_register(NULL, &slowck->hw);
 	if (IS_ERR(clk))
 		kfree(slowck);
-	else
-		slow_clk = clk;
 
 	return clk;
 }
@@ -470,25 +465,3 @@ void __init of_at91sam9260_clk_slow_setup(struct device_node *np,
 
 	of_clk_add_provider(np, of_clk_src_simple_get, clk);
 }
-
-/*
- * FIXME: All slow clk users are not properly claiming it (get + prepare +
- * enable) before using it.
- * If all users properly claiming this clock decide that they don't need it
- * anymore (or are removed), it is disabled while faulty users are still
- * requiring it, and the system hangs.
- * Prevent this clock from being disabled until all users are properly
- * requesting it.
- * Once this is done we should remove this function and the slow_clk variable.
- */
-static int __init of_at91_clk_slow_retain(void)
-{
-	if (!slow_clk)
-		return 0;
-
-	__clk_get(slow_clk);
-	clk_prepare_enable(slow_clk);
-
-	return 0;
-}
-arch_initcall(of_at91_clk_slow_retain);
-- 
2.1.4

Re: [PATCH 20/20] clk: at91: Revert "keep slow clk enabled to prevent system hang"

[Michael Turquette]

Quoting Alexandre Belloni (2015-07-29 17:22:06)
> Commit dca1a4b5ff6e ("clk: at91: keep slow clk enabled to prevent system
> hang") added a workaround for the slow clock as it is not properly handled
> by its users.
> 
> Now that the slow clock is taken properly by the drivers, this workaround
> is not necessary anymore, revert it.
> 
> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> ---
> Cc: Michael Turquette <mturquette@baylibre.com>
> Cc: Stephen Boyd <sboyd@codeaurora.org>
> Cc: linux-clk@vger.kernel.org
>  drivers/clk/at91/clk-slow.c | 27 ---------------------------
>  1 file changed, 27 deletions(-)
> 
> diff --git a/drivers/clk/at91/clk-slow.c b/drivers/clk/at91/clk-slow.c
> index 98a84a865fe1..2c59d6a64dd5 100644
> --- a/drivers/clk/at91/clk-slow.c
> +++ b/drivers/clk/at91/clk-slow.c
> @@ -70,7 +70,6 @@ struct clk_sam9x5_slow {
>  
>  #define to_clk_sam9x5_slow(hw) container_of(hw, struct clk_sam9x5_slow, hw)
>  
> -static struct clk *slow_clk;
>  

Might want to remove one extra line of white space?

>  static int clk_slow_osc_prepare(struct clk_hw *hw)
>  {
> @@ -358,8 +357,6 @@ at91_clk_register_sam9x5_slow(void __iomem *sckcr,
>         clk = clk_register(NULL, &slowck->hw);
>         if (IS_ERR(clk))
>                 kfree(slowck);
> -       else
> -               slow_clk = clk;
>  
>         return clk;
>  }
> @@ -436,8 +433,6 @@ at91_clk_register_sam9260_slow(struct at91_pmc *pmc,
>         clk = clk_register(NULL, &slowck->hw);
>         if (IS_ERR(clk))
>                 kfree(slowck);
> -       else
> -               slow_clk = clk;
>  
>         return clk;
>  }
> @@ -470,25 +465,3 @@ void __init of_at91sam9260_clk_slow_setup(struct device_node *np,
>  
>         of_clk_add_provider(np, of_clk_src_simple_get, clk);
>  }
> -
> -/*
> - * FIXME: All slow clk users are not properly claiming it (get + prepare +
> - * enable) before using it.
> - * If all users properly claiming this clock decide that they don't need it
> - * anymore (or are removed), it is disabled while faulty users are still
> - * requiring it, and the system hangs.
> - * Prevent this clock from being disabled until all users are properly
> - * requesting it.
> - * Once this is done we should remove this function and the slow_clk variable.
> - */
> -static int __init of_at91_clk_slow_retain(void)
> -{
> -       if (!slow_clk)
> -               return 0;
> -
> -       __clk_get(slow_clk);
> -       clk_prepare_enable(slow_clk);
> -
> -       return 0;
> -}
> -arch_initcall(of_at91_clk_slow_retain);

This is a cool series. Thanks. Feel free to add my Ack, or we can take
this through clk-next once the other patches are applied.

Regards,
Mike

> -- 
> 2.1.4
> 
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