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Message-ID: <CAMuHMdWrJ9LmDqBQYvNVs7yY78Po0sTGc=MUu9+tau2frJ9Ytw@mail.gmail.com>
Date: Mon, 17 Feb 2020 16:11:35 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Khouloud Touil <ktouil@...libre.com>,
Bartosz Golaszewski <bgolaszewski@...libre.com>,
Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
baylibre-upstreaming@...ups.io,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@...r.kernel.org>,
Linux I2C <linux-i2c@...r.kernel.org>,
Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v4 2/5] nvmem: add support for the write-protect pin
Hi Bartosz,
On Mon, Feb 17, 2020 at 3:34 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
> czw., 30 sty 2020 o 09:06 Geert Uytterhoeven <geert@...ux-m68k.org> napisaĆ(a):
> > On Tue, Jan 7, 2020 at 10:30 AM Khouloud Touil <ktouil@...libre.com> wrote:
> > > The write-protect pin handling looks like a standard property that
> > > could benefit other users if available in the core nvmem framework.
> > >
> > > Instead of modifying all the memory drivers to check this pin, make
> > > the NVMEM subsystem check if the write-protect GPIO being passed
> > > through the nvmem_config or defined in the device tree and pull it
> > > low whenever writing to the memory.
> > >
> > > There was a suggestion for introducing the gpiodesc from pdata, but
> > > as pdata is already removed it could be replaced by adding it to
> > > nvmem_config.
> > >
> > > Reference: https://lists.96boards.org/pipermail/dev/2018-August/001056.html
> > >
> > > Signed-off-by: Khouloud Touil <ktouil@...libre.com>
> > > Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
> > > Acked-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> >
> > Thanks for your patch!
> >
> > > --- a/drivers/nvmem/core.c
> > > +++ b/drivers/nvmem/core.c
> > > @@ -15,6 +15,7 @@
> > > #include <linux/module.h>
> > > #include <linux/nvmem-consumer.h>
> > > #include <linux/nvmem-provider.h>
> > > +#include <linux/gpio/consumer.h>
> > > #include <linux/of.h>
> > > #include <linux/slab.h>
> > > #include "nvmem.h"
> > > @@ -54,8 +55,14 @@ static int nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset,
> > > static int nvmem_reg_write(struct nvmem_device *nvmem, unsigned int offset,
> > > void *val, size_t bytes)
> > > {
> > > - if (nvmem->reg_write)
> > > - return nvmem->reg_write(nvmem->priv, offset, val, bytes);
> > > + int ret;
> > > +
> > > + if (nvmem->reg_write) {
> > > + gpiod_set_value_cansleep(nvmem->wp_gpio, 0);
> > > + ret = nvmem->reg_write(nvmem->priv, offset, val, bytes);
> > > + gpiod_set_value_cansleep(nvmem->wp_gpio, 1);
> > > + return ret;
> > > + }
> > >
> > > return -EINVAL;
> > > }
> > > @@ -338,6 +345,14 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
> > > kfree(nvmem);
> > > return ERR_PTR(rval);
> > > }
> > > + if (config->wp_gpio)
> > > + nvmem->wp_gpio = config->wp_gpio;
> > > + else
> > > + nvmem->wp_gpio = gpiod_get_optional(config->dev, "wp",
> > > + GPIOD_OUT_HIGH);
> >
> > Shouldn't this GPIO be released in nvmem_release(), by calling gpiod_put()?
> >
>
> Hi Geert,
>
> Khouloud already sent out a patch but I think it still doesn't fix all
> the problems.
>
> While we should call gpiod_put() for the descs we request - we must
> not do it for the desc we get over the config structure. Unless... we
That's true.
> make descs reference counted with kref and add gpiod_ref() helper.
> That way we could increase the reference counter in the upper branch
> of the if and not do it in the lower. Calling gpiod_put() would
> internally call kref_put(). Does it make sense? I think that a
> function that's called gpiod_put() but doesn't really use reference
> counting is misleading anyway.
Yep.
> > Once that's implemented, I assume it will be auto-released on registration
> > failure by the call to put_device()?
>
> No, I think this is another leak - why would put_device() lead to
> freeing any resources? Am I missing something?
Sorry, I don't remember why I wrote that part...
Anyway, requested GPIOs should be released on failure, and on
unregistration.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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