linux-kernel - Re: [PATCH v3 3/3] misc: eeprom: at24: register nvmem only after eeprom is ready to use

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Date:   Mon, 31 Aug 2020 20:24:43 +0300
From:   Vadym Kochan <vadym.kochan@...ision.eu>
To:     Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/3] misc: eeprom: at24: register nvmem only after
 eeprom is ready to use

Hi Bartosz,

On Mon, Aug 31, 2020 at 07:21:39PM +0200, Bartosz Golaszewski wrote:
> On Mon, Aug 31, 2020 at 3:56 AM Vadym Kochan <vadym.kochan@...ision.eu> wrote:
> >
> > During nvmem_register() the nvmem core sends notifications when:
> >
> >     - cell added
> >     - nvmem added
> >
> > and during these notifications some callback func may access the nvmem
> > device, which will fail in case of at24 eeprom because regulator and pm
> > are enabled after nvmem_register().
> >
> > Signed-off-by: Vadym Kochan <vadym.kochan@...ision.eu>
> > ---
> > v3:
> >     1) at24 driver enables regulator and pm state machine after nvmem
> >        registration which does not allow to use it on handing NVMEM_PRE_ADD event.
> >
> >  drivers/misc/eeprom/at24.c | 11 +++++++----
> >  1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> > index 2591c21b2b5d..26a23abc053d 100644
> > --- a/drivers/misc/eeprom/at24.c
> > +++ b/drivers/misc/eeprom/at24.c
> > @@ -692,10 +692,6 @@ static int at24_probe(struct i2c_client *client)
> >         nvmem_config.word_size = 1;
> >         nvmem_config.size = byte_len;
> >
> > -       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> > -       if (IS_ERR(at24->nvmem))
> > -               return PTR_ERR(at24->nvmem);
> > -
> >         i2c_set_clientdata(client, at24);
> >
> >         err = regulator_enable(at24->vcc_reg);
> > @@ -708,6 +704,13 @@ static int at24_probe(struct i2c_client *client)
> >         pm_runtime_set_active(dev);
> >         pm_runtime_enable(dev);
> >
> > +       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> > +       if (IS_ERR(at24->nvmem)) {
> > +               pm_runtime_disable(dev);
> > +               regulator_disable(at24->vcc_reg);
> > +               return PTR_ERR(at24->nvmem);
> > +       }
> > +
> >         /*
> >          * Perform a one-byte test read to verify that the
> >          * chip is functional.
> > --
> > 2.17.1
> >
> 
> Good catch! Thanks for the patch. Can I queue it for fixes
> independently from the earlier patches in this series?
> 
> Bart

Sure.

Regards,
Vadym Kochan