linux-kernel - Re: [PATCH v3 1/5] clk: Ingenic: Remove unnecessary spinlock when reading registers.

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Date:   Sun, 15 Dec 2019 22:11:58 +0800
From:   Zhou Yanjie <zhouyanjie@...yeetech.com>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        robh+dt@...nel.org, paul.burton@...s.com, paulburton@...nel.org,
        mturquette@...libre.com, sboyd@...nel.org, mark.rutland@....com,
        sernia.zhou@...mail.com, zhenwenjin@...il.com
Subject: Re: [PATCH v3 1/5] clk: Ingenic: Remove unnecessary spinlock when
 reading registers.

Hi Paul,

On 2019年12月15日 02:07, Paul Cercueil wrote:
> Hi Zhou,
>
> You can also remove the locks around ingenic_cgu_gate_get(), they are 
> useless. Then also edit the doc of this function as currently it says 
> that the caller must hold the lock.
>

Sure, I'll remove it in v4.

Thanks and best regards!

> -Paul
>
>
> Le sam., déc. 14, 2019 at 23:33, 周琰杰 (Zhou Yanjie) 
> <zhouyanjie@...yeetech.com> a écrit :
>> It is not necessary to use spinlock when reading registers,
>> so remove it from cgu.c.
>>
>> Suggested-by: Paul Cercueil <paul@...pouillou.net>
>> Suggested-by: Paul Burton <paulburton@...nel.org>
>> Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@...yeetech.com>
>> ---
>>
>> Notes:
>>     v2:
>>     New patch.
>>
>>     v2->v3:
>>     Adjust order from [5/5] in v2 to [1/5] in v3.
>>
>>  drivers/clk/ingenic/cgu.c | 6 ------
>>  1 file changed, 6 deletions(-)
>>
>> diff --git a/drivers/clk/ingenic/cgu.c b/drivers/clk/ingenic/cgu.c
>> index 6e96303..8bd3998 100644
>> --- a/drivers/clk/ingenic/cgu.c
>> +++ b/drivers/clk/ingenic/cgu.c
>> @@ -76,16 +76,13 @@ ingenic_pll_recalc_rate(struct clk_hw *hw, 
>> unsigned long parent_rate)
>>      const struct ingenic_cgu_pll_info *pll_info;
>>      unsigned m, n, od_enc, od;
>>      bool bypass;
>> -    unsigned long flags;
>>      u32 ctl;
>>
>>      clk_info = &cgu->clock_info[ingenic_clk->idx];
>>      BUG_ON(clk_info->type != CGU_CLK_PLL);
>>      pll_info = &clk_info->pll;
>>
>> -    spin_lock_irqsave(&cgu->lock, flags);
>>      ctl = readl(cgu->base + pll_info->reg);
>> -    spin_unlock_irqrestore(&cgu->lock, flags);
>>
>>      m = (ctl >> pll_info->m_shift) & GENMASK(pll_info->m_bits - 1, 0);
>>      m += pll_info->m_offset;
>> @@ -259,12 +256,9 @@ static int ingenic_pll_is_enabled(struct clk_hw 
>> *hw)
>>      struct ingenic_cgu *cgu = ingenic_clk->cgu;
>>      const struct ingenic_cgu_clk_info *clk_info = 
>> to_clk_info(ingenic_clk);
>>      const struct ingenic_cgu_pll_info *pll_info = &clk_info->pll;
>> -    unsigned long flags;
>>      u32 ctl;
>>
>> -    spin_lock_irqsave(&cgu->lock, flags);
>>      ctl = readl(cgu->base + pll_info->reg);
>> -    spin_unlock_irqrestore(&cgu->lock, flags);
>>
>>      return !!(ctl & BIT(pll_info->enable_bit));
>>  }
>> -- 
>> 2.7.4
>>
>