linux-kernel - Re: [PATCH v2 14/21] ARM: tegra: clock: Refcount periph clock enables

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Date:	Sun, 20 Feb 2011 23:06:01 -0800
From:	Colin Cross <ccross@...roid.com>
To:	Olof Johansson <olof@...om.net>
Cc:	linux-tegra@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	konkers@...roid.com, Russell King <linux@....linux.org.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 14/21] ARM: tegra: clock: Refcount periph clock enables

On Sun, Feb 20, 2011 at 8:18 PM, Olof Johansson <olof@...om.net> wrote:
> Hi,
>
> On Sat, Feb 19, 2011 at 2:26 PM, Colin Cross <ccross@...roid.com> wrote:
>> Some peripheral clocks share enable bits.  Refcount the enables so
>> that calling clk_disable on one clock will not turn off another
>> clock.
>>
>> Signed-off-by: Colin Cross <ccross@...roid.com>
>> ---
>>  arch/arm/mach-tegra/tegra2_clocks.c |   35 +++++++++++++++++++++++++++++------
>>  1 files changed, 29 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm/mach-tegra/tegra2_clocks.c b/arch/arm/mach-tegra/tegra2_clocks.c
>> index 196c249..2734889 100644
>> --- a/arch/arm/mach-tegra/tegra2_clocks.c
>> +++ b/arch/arm/mach-tegra/tegra2_clocks.c
>> @@ -154,6 +154,12 @@ static void __iomem *reg_pmc_base = IO_ADDRESS(TEGRA_PMC_BASE);
>>  */
>>  static DEFINE_SPINLOCK(clock_register_lock);
>>
>> +/*
>> + * Some peripheral clocks share an enable bit, so refcount the enable bits
>> + * in registers CLK_ENABLE_L, CLK_ENABLE_H, and CLK_ENABLE_U
>> + */
>> +static int tegra_periph_clk_enable_refcount[3 * 32];
>
> Given that this is always locked when incrementing/decrementing,
> should it just be switched to an array of atomics instead?
No, the spinlock needs to be held between the increment/decrement and
test and the actual register write.  The spinlock release in the
enable function needs to be moved after the register write.
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