linux-kernel - Re: [PATCH v2] i2c: stm32f7: Add atomic

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Message-Id: <5E10F2AD-6D7E-4F2F-ACEB-B6FD3C71C85D@geanix.com>
Date:   Wed, 16 Aug 2023 09:02:20 +0200
From:   Sean Nyekjaer <sean@...nix.com>
To:     Alain Volmat <alain.volmat@...s.st.com>
Cc:     Pierre-Yves MORDRET <pierre-yves.mordret@...s.st.com>,
        Andi Shyti <andi.shyti@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        linux-i2c@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] i2c: stm32f7: Add atomic_xfer method to driver

Hi Alain,

Thanks for the review

> On 2 Aug 2023, at 12.07, Alain Volmat <alain.volmat@...s.st.com> wrote:
> 
> Hi Sean,
> 
> sorry for the delay for this review.  Thank you Andi for
> the review as well.

Also from my side :) Vacation.

> 
> Few other comments in addition to what Andi already mentioned.
> 
> On Tue, Jul 18, 2023 at 12:54:35PM +0200, Sean Nyekjaer wrote:
>> Add an atomic_xfer method to the driver so that it behaves correctly
>> when controlling a PMIC that is responsible for device shutdown.
>> 
>> The atomic_xfer method added is similar to the one from the i2c-mv64xxx
>> driver. When running an atomic_xfer a bool flag in the driver data is
>> set, the interrupt is not unmasked on transfer start, and the IRQ
>> handler is manually invoked while waiting for pending transfers to
>> complete.
>> 
>> Signed-off-by: Sean Nyekjaer <sean@...nix.com>
>> ---
>> Changes since v1:
>> - Removed dma in atomic
>> 
>> drivers/i2c/busses/i2c-stm32f7.c | 111 ++++++++++++++++++++++---------
>> 1 file changed, 78 insertions(+), 33 deletions(-)
>> 
>> diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
>> index e897d9101434..d944b8f85d1c 100644
>> --- a/drivers/i2c/busses/i2c-stm32f7.c
>> +++ b/drivers/i2c/busses/i2c-stm32f7.c
>> @@ -357,6 +357,7 @@ struct stm32f7_i2c_dev {
>> u32 dnf_dt;
>> u32 dnf;
>> struct stm32f7_i2c_alert *alert;
>> + bool atomic;
> 
> I am wondering if this atomic really needs to be within the struct.
> It could well be given as last arg of stm32f7_i2c_xfer_core and
> stm32f7_i2c_xfer functions.

Agree.

> 
> 
>> };
>> 
>> 

[ … ]

>> @@ -1670,7 +1676,22 @@ static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
>> return IRQ_HANDLED;
>> }
>> 
>> -static int stm32f7_i2c_xfer(struct i2c_adapter *i2c_adap,
>> +static int stm32f7_i2c_wait_polling(struct stm32f7_i2c_dev *i2c_dev)
>> +{
>> + ktime_t timeout = ktime_add_ms(ktime_get(), i2c_dev->adap.timeout);
>> +
>> + while (ktime_compare(ktime_get(), timeout) < 0) {
>> + udelay(5);
>> + stm32f7_i2c_isr_event(0, i2c_dev);
>> +
>> + if (try_wait_for_completion(&i2c_dev->complete))
>> + return 1;
> 
> I agree with the complete / wait_for_completion approach since it allows
> to keep most of code common by manually calling the isr_event for
> checking status bits.  However what about using completion_done instead
> of try_wait_for_completion here ? This shouldn't change much since
> anyway there is a reinit_completion at the beginning of the xfer
> function, but at least function naming feels better since not refering
> to waiting ..

I’ll take a look at the completion_done()

> 
>> + }
>> 

[ … ]

/Sean