From: jiada_wang@mentor•com (Jiada Wang)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] ARM: imx: powerdown PLL before changing of its setting
Date: Tue, 20 May 2014 00:00:46 -0700 [thread overview]
Message-ID: <537AFD9E.9080203@mentor.com> (raw)
In-Reply-To: <537AF384.9070900@de.bosch.com>
Hi Dirk and Fabio
On 05/19/2014 11:17 PM, Dirk Behme wrote:
> Hi Fabio,
>
> On 19.05.2014 19:31, Fabio Estevam wrote:
>> Hi Jiada,
>>
>> On Wed, May 14, 2014 at 6:36 AM, Jiada Wang <jiada_wang@mentor•com>
>> wrote:
>>> According to i.MX6 user manual, "Before changing the PLL setting,
>>> power it down. Power up the PLL after the change"
>>> But currently PLL setting is being updated without power-down
>>> it first. This may end up with improper output/gitches which
>>> prevents furture operation.
>>>
>>> Signed-off-by: Jiada Wang <jiada_wang@mentor•com>
>>> ---
>>> arch/arm/mach-imx/clk-pllv3.c | 72
>>> +++++++++++++++++++++++++++++++++++++++----
>>> 1 file changed, 66 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/arch/arm/mach-imx/clk-pllv3.c
>>> b/arch/arm/mach-imx/clk-pllv3.c
>>> index 6136405..f77edd6 100644
>>> --- a/arch/arm/mach-imx/clk-pllv3.c
>>> +++ b/arch/arm/mach-imx/clk-pllv3.c
>>> @@ -67,6 +67,42 @@ static int clk_pllv3_wait_lock(struct clk_pllv3 *pll)
>>> return readl_relaxed(pll->base) & BM_PLL_LOCK ? 0 : -ETIMEDOUT;
>>> }
>>>
>>> +static void clk_pllv3_powerdown(struct clk_pllv3 *pll)
>>> +{
>>> + u32 val;
>>> +
>>> + val = readl_relaxed(pll->base);
>>> + val |= BM_PLL_BYPASS;
>>> + writel_relaxed(val, pll->base);
>>> +
>>> + if (pll->powerup_set)
>>> + val &= ~BM_PLL_POWER;
>>> + else
>>> + val |= BM_PLL_POWER;
>>> + writel_relaxed(val, pll->base);
>>> +}
>>> +
>>> +static int clk_pllv3_powerrestore(struct clk_pllv3 *pll, u32 power,
>>> u32 bypass)
>>> +{
>>> + u32 val;
>>> + int ret;
>>> +
>>> + val = readl_relaxed(pll->base);
>>> + val &= ~BM_PLL_POWER;
>>
>> Shouldn't this be:
>> if (pll->powerup_set)
>> val |= BM_PLL_POWER;
>> else
>> val &= ~BM_PLL_POWER;
>>
>
> Jiada will correct me if I'm wrong, but to my understanding the job of
> this function is to *restore* the previously configured power state (not
> to set any particular one).
>
> The previously configured power state is passed in 'u32 power'. So we
> just mask out the POWER bit here to be able to restore the old power
> state, independent if it is 0 or 1. So I would think
>
> + val = readl_relaxed(pll->base);
> + val &= ~BM_PLL_POWER;
> + val |= power;
> + writel_relaxed(val, pll->base);
>
> is correct here.
>
> Best regards
>
> Dirk
>
Yes, this function restores power state as well as bypass state,
as set_rate() may be called before prepare(),
so we have no idea about power and bypass state here.
Thanks,
Jiada
prev parent reply other threads:[~2014-05-20 7:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-14 9:36 [PATCH] ARM: imx: powerdown PLL before changing of its setting Jiada Wang
2014-05-19 17:31 ` Fabio Estevam
2014-05-20 6:17 ` Dirk Behme
2014-05-20 7:00 ` Jiada Wang [this message]
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