linux-kernel - Re: [PATCH] spi: remove spin_lock

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Date:   Sat, 16 Apr 2022 08:49:13 -0700
From:   Tom Rix <trix@...hat.com>
To:     郭力豪 <lhjeff911@...il.com>
Cc:     Mark Brown <broonie@...nel.org>, linux-spi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        呂芳騰LuWells <wells.lu@...plus.com>,
        "lh.kuo" <lh.kuo@...plus.com>, nathan@...nel.org
Subject: Re: [PATCH] spi: remove spin_lock_irq in the irq procress


On 4/14/22 6:16 AM, 郭力豪 wrote:
> Hi Tom :
>
>      This SPI driver only handles one transfer at a time.
> That's why locks are not needed.

Please add this statement to the commit log.

In a commit log, not only do I look for what was changed but also why 
the change was made.

Tom

>
>
> Li-hao Kuo
>
> Tom Rix <trix@...hat.com> 於 2022年4月13日 週三 下午7:45寫道：
>>
>> On 4/12/22 6:38 PM, Li-hao Kuo wrote:
>>> - remove spin_lock_irq and spin_unlock_irq in the irq funciton
>> function
>>
>> I was expecting a statement on why is the lock is not needed.
>>
>> Could you add one ?
>>
>> Tom
>>
>>> Signed-off-by: Li-hao Kuo <lhjeff911@...il.com>
>>> ---
>>>    drivers/spi/spi-sunplus-sp7021.c | 4 +---
>>>    1 file changed, 1 insertion(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/spi/spi-sunplus-sp7021.c b/drivers/spi/spi-sunplus-sp7021.c
>>> index f989f7b..120623c 100644
>>> --- a/drivers/spi/spi-sunplus-sp7021.c
>>> +++ b/drivers/spi/spi-sunplus-sp7021.c
>>> @@ -199,8 +199,6 @@ static irqreturn_t sp7021_spi_master_irq(int irq, void *dev)
>>>        if (tx_len == 0 && total_len == 0)
>>>                return IRQ_NONE;
>>>
>>> -     spin_lock_irq(&pspim->lock);
>>> -
>>>        rx_cnt = FIELD_GET(SP7021_RX_CNT_MASK, fd_status);
>>>        if (fd_status & SP7021_RX_FULL_FLAG)
>>>                rx_cnt = pspim->data_unit;
>>> @@ -239,7 +237,7 @@ static irqreturn_t sp7021_spi_master_irq(int irq, void *dev)
>>>
>>>        if (isrdone)
>>>                complete(&pspim->isr_done);
>>> -     spin_unlock_irq(&pspim->lock);
>>> +
>>>        return IRQ_HANDLED;
>>>    }
>>>