lkml.org 
[lkml]   [2018]   [May]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: [PATCH 5/6] mtd: rawnand: ams-delta: use GPIO lookup table
    Date
    On Saturday, May 19, 2018 8:00:38 PM CEST Andy Shevchenko wrote:
    > On Sat, May 19, 2018 at 2:15 AM, Janusz Krzysztofik <jmkrzyszt@gmail.com>
    wrote:
    > > On Friday, May 18, 2018 11:21:14 PM CEST Andy Shevchenko wrote:
    > >> On Sat, May 19, 2018 at 12:09 AM, Janusz Krzysztofik
    > >>
    > >> <jmkrzyszt@gmail.com> wrote:
    > >> > + gpiod_rdy = devm_gpiod_get_optional(&pdev->dev, "rdy",
    > >> > GPIOD_IN);
    > >> > + if (!IS_ERR_OR_NULL(gpiod_rdy)) {
    > >>
    > >> So, is it optional or not at the end?
    > >> If it is, why do we check for NULL?
    > >
    > > As far as I can understand, nand_chip->dev_ready() callback is optional.
    > > That's why I decided to use the _optional variant of devm_gpiod_get(). In
    > > case of ams-delta, the dev_ready() callback depends on availability of
    > > the 'rdy' GPIO pin. As a consequence, I'm checking for both NULL and ERR
    > > in order to decide if dev_ready() will be supported.
    > >
    > > I can pretty well replace it with the standard form and check for ERR only
    > > if the purpose of the _optional form is different.
    >
    > NULL check in practice discards the _optional part of gpiod_get(). So,
    > either you use non-optional variant and decide how to handle an
    > errors, or user _optional w/o NULL check.

    OK, I'm going to use something like the below while submitting v2:

    - gpiod_rdy = devm_gpiod_get_optional(&pdev->dev, "rdy", GPIOD_IN);
    - if (!IS_ERR_OR_NULL(gpiod_rdy)) {
    - this->dev_ready = ams_delta_nand_ready;
    - } else {
    - this->dev_ready = NULL;
    - pr_notice("Couldn't request gpio for Delta NAND ready.\n");
    + priv->gpiod_rdy = devm_gpiod_get_optional(&pdev->dev, "rdy",
    + GPIOD_IN);
    + if (IS_ERR(priv->gpiod_rdy)) {
    + err = PTR_ERR(priv->gpiod_nwp);
    + dev_warn(&pdev->dev, "RDY GPIO request failed (%d)\n", err);
    + goto err_gpiod;
    }

    + if (priv->gpiod_rdy)
    + this->dev_ready = ams_delta_nand_ready;

    >
    > >> > +err_gpiod:
    > >> > + if (err == -ENODEV || err == -ENOENT)
    > >> > + err = -EPROBE_DEFER;
    > >>
    > >> Hmm...
    > >
    > > Amstrad Delta uses gpio-mmio driver. Unfortunatelty that driver is not
    > > availble before device init phase, unlike other crucial GPIO drivers which
    > > are initialized earlier, e.g. during the postcore or at latetst the
    > > subsys phase. Hence, devices which depend on GPIO pins provided by
    > > gpio-mmio must either be declared late or fail softly so they get another
    > > chance of being probed succesfully.
    > >
    > > I thought of replacing the gpio-mmio platform driver with bgpio functions
    > > it exports but for now I haven't implemented it, not even shared the
    > > idea.
    > >
    > > Does it really hurt to return -EPROBE_DEFER if a GPIO pin can't be
    > > obtained?
    > I'm only concerned if it would be an infinite defer in the case when
    > driver will never appear.
    > But I don't remember the details.

    Deferred probes are handled effectively during late_initcall, no risk of
    infinite defer, see drivers/base/dd.c for details.

    Thanks,
    Janusz



    \
     
     \ /
      Last update: 2018-05-19 23:56    [W:2.618 / U:0.504 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site