linux-kernel - Re: [PATCH v3 5/6] i2c: Add Actions Semiconductor Owl family S900 I2C driver

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Date:   Sun, 1 Jul 2018 12:11:54 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     Wolfram Sang <wsa@...-dreams.de>, Rob Herring <robh+dt@...nel.org>,
        Andreas Färber <afaerber@...e.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        刘炜 <liuwei@...ions-semi.com>,
        mp-cs@...ions-semi.com, 96boards@...obotics.com,
        devicetree <devicetree@...r.kernel.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        amit.kucheria@...aro.org,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        hzhang@...obotics.com, bdong@...obotics.com,
        Mani Sadhasivam <manivannanece23@...il.com>,
        Thomas Liau <thomas.liau@...ions-semi.com>,
        jeff.chen@...ions-semi.com
Subject: Re: [PATCH v3 5/6] i2c: Add Actions Semiconductor Owl family S900 I2C driver

On Sun, Jul 1, 2018 at 11:41 AM, Manivannan Sadhasivam
<manivannan.sadhasivam@...aro.org> wrote:
> On Sun, Jul 01, 2018 at 01:43:33PM +0530, Manivannan Sadhasivam wrote:
>> On Sun, Jul 01, 2018 at 12:11:00AM +0300, Andy Shevchenko wrote:
>> > On Sat, Jun 30, 2018 at 4:33 PM, Manivannan Sadhasivam
>> > <manivannan.sadhasivam@...aro.org> wrote:
>> > > Add Actions Semiconductor Owl family S900 I2C driver.

>> > > +static int owl_i2c_reset(struct owl_i2c_dev *i2c_dev)
>> > > +{
>> >
>> > > +       mdelay(1);
>> >
>> > But now, since it's not used in atomic context, we may switch to
>> > usleep_range() / msleep() instead.
>> >
>>
>> okay, will use msleep()
>>
>
> Just realised, I have to use spinlock for the entire owl_i2c_master_xfer
> function, so can't use sleep* for delay.
>
>> > > +       owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
>> > > +                               OWL_I2C_CTL_EN, true);
>> > > +
>> >
>> > > +       /* Wait 50ms for FIFO reset complete */
>> > > +       do {
>> >
>> > > +               mdelay(1);
>> >
>> > Especially in this case it's very important.
>> >
>>
>> Okay.
>
> Same here, but I'm not sure about the latency. What is your suggestion?

Look at other i2c bus drivers, check with data sheet you have, try to
refactor / redesign code that wouldn't need to sleep so long in atomic
context.


-- 
With Best Regards,
Andy Shevchenko