Re: [PATCH/RFC] treewide: Fix instantiation of devices in DT overlay

[Saravana Kannan <saravanak@google.com>]

On Fri, Mar 17, 2023 at 5:36 PM Saravana Kannan <saravanak@google.com> wrote:
>
> On Fri, Mar 17, 2023 at 3:33 AM Geert Uytterhoeven
> <geert+renesas@glider.be> wrote:
> >
> > When loading a DT overlay that creates a device, the device is not
> > instantiated, unless the DT overlay is unloaded and reloaded again.
> >
> > Saravana explains:
> >   Basically for all overlays (I hope the function is only used for
> >   overlays) we assume all nodes are NOT devices until they actually
> >   get added as a device. Don't review the code, it's not meant to be :)
> >
> > Based on a hacky patch by Saravana Kannan, which covered only platform
> > and spi devices.
> >
> > Fixes: 4a032827daa89350 ("of: property: Simplify of_link_to_phandle()")
> > Link: https://lore.kernel.org/all/CAGETcx_+rhHvaC_HJXGrr5_WAd2+k5f=rWYnkCZ6z5bGX-wj4w@mail.gmail.com
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > ---
> > Marked RFC as Saravana said this is an ugly hack.
> > Still, this is a regression in v6.3-rc1 that should be fixed.
>
> Thanks for making sure this isn't forgotten.
>
> I thought about this a bit more and I've decided what I gave earlier
> isn't really too much of a hack. The other option is to handle the
> clearing of the flag at the driver core level, but we incur these
> additional instructions for all devices instead of just the overlay
> case. But the benefit is that if more busses add overlay support in
> the future, they won't need to remember to clear the flag in those
> instances too. But they'll probably start off by looking at the
> existing platform bus case, so they'll get it right.
>
> I'll continue the pondering next week and maybe test it on my device
> to make sure it's not doing anything weird for non-overlay cases.
>

Geert,

I think we should stick with the original style of fix I suggested.
So, basically your patch set. Are you planning on sending a non-RFC or
do you want me to do it?

-Saravana

> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -3611,6 +3611,15 @@ int device_add(struct device *dev)
>          */
>         if (dev->fwnode && !dev->fwnode->dev) {
>                 dev->fwnode->dev = dev;
> +               /*
> +                * If a fwnode was initially marked as not a device, but we
> +                * clearly have a device added for it that can probe, then clear
> +                * the flag so fw_devlink will continue linking consumers to
> +                * this device. This code path is really expected to run only
> +                * for DT overlays.
> +                */
> +               if (dev->bus)
> +                       dev->fwnode.flags &= ~FWNODE_FLAG_NOT_DEVICE
>                 fw_devlink_link_device(dev);
>         }
>
> diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
> index 07d93753b12f..f715b59d9bf3 100644
> --- a/drivers/of/dynamic.c
> +++ b/drivers/of/dynamic.c
> @@ -226,6 +226,11 @@ static void __of_attach_node(struct device_node *np)
>         np->sibling = np->parent->child;
>         np->parent->child = np;
>         of_node_clear_flag(np, OF_DETACHED);
> +       /*
> +        * Ask fw_devlink to assume any new node is not a device. Driver core
> +        * will clear this flag if the assumption turns out to be wrong.
> +        */
> +       np->fwnode.flags |= FWNODE_FLAG_NOT_DEVICE;
>  }
>
>
>
>
> > ---
> >  drivers/bus/imx-weim.c    | 1 +
> >  drivers/i2c/i2c-core-of.c | 1 +
> >  drivers/of/dynamic.c      | 1 +
> >  drivers/of/platform.c     | 1 +
> >  drivers/spi/spi.c         | 1 +
> >  5 files changed, 5 insertions(+)
> >
> > diff --git a/drivers/bus/imx-weim.c b/drivers/bus/imx-weim.c
> > index 2a6b4f676458612e..71d8807170fa9f29 100644
> > --- a/drivers/bus/imx-weim.c
> > +++ b/drivers/bus/imx-weim.c
> > @@ -329,6 +329,7 @@ static int of_weim_notify(struct notifier_block *nb, unsigned long action,
> >                                  "Failed to setup timing for '%pOF'\n", rd->dn);
> >
> >                 if (!of_node_check_flag(rd->dn, OF_POPULATED)) {
> > +                       rd->dn->fwnode.flags &= ~FWNODE_FLAG_NOT_DEVICE;
> >                         if (!of_platform_device_create(rd->dn, NULL, &pdev->dev)) {
> >                                 dev_err(&pdev->dev,
> >                                         "Failed to create child device '%pOF'\n",
> > diff --git a/drivers/i2c/i2c-core-of.c b/drivers/i2c/i2c-core-of.c
> > index bce6b796e04c2ca0..79a0d47010ba0b20 100644
> > --- a/drivers/i2c/i2c-core-of.c
> > +++ b/drivers/i2c/i2c-core-of.c
> > @@ -178,6 +178,7 @@ static int of_i2c_notify(struct notifier_block *nb, unsigned long action,
> >                         return NOTIFY_OK;
> >                 }
> >
> > +               rd->dn->fwnode.flags &= ~FWNODE_FLAG_NOT_DEVICE;
> >                 client = of_i2c_register_device(adap, rd->dn);
> >                 if (IS_ERR(client)) {
> >                         dev_err(&adap->dev, "failed to create client for '%pOF'\n",
> > diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
> > index 07d93753b12f5f4d..e311d406b1705306 100644
> > --- a/drivers/of/dynamic.c
> > +++ b/drivers/of/dynamic.c
> > @@ -226,6 +226,7 @@ static void __of_attach_node(struct device_node *np)
> >         np->sibling = np->parent->child;
> >         np->parent->child = np;
> >         of_node_clear_flag(np, OF_DETACHED);
> > +       np->fwnode.flags |= FWNODE_FLAG_NOT_DEVICE;
> >  }
> >
> >  /**
> > diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> > index b2bd2e783445dd78..17c92cbfb62ee3ef 100644
> > --- a/drivers/of/platform.c
> > +++ b/drivers/of/platform.c
> > @@ -737,6 +737,7 @@ static int of_platform_notify(struct notifier_block *nb,
> >                 if (of_node_check_flag(rd->dn, OF_POPULATED))
> >                         return NOTIFY_OK;
> >
> > +               rd->dn->fwnode.flags &= ~FWNODE_FLAG_NOT_DEVICE;
> >                 /* pdev_parent may be NULL when no bus platform device */
> >                 pdev_parent = of_find_device_by_node(rd->dn->parent);
> >                 pdev = of_platform_device_create(rd->dn, NULL,
> > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> > index 1a65f96fe2aff591..7bd053a32fad1a3c 100644
> > --- a/drivers/spi/spi.c
> > +++ b/drivers/spi/spi.c
> > @@ -4480,6 +4480,7 @@ static int of_spi_notify(struct notifier_block *nb, unsigned long action,
> >                         return NOTIFY_OK;
> >                 }
> >
> > +               rd->dn->fwnode.flags &= ~FWNODE_FLAG_NOT_DEVICE;
> >                 spi = of_register_spi_device(ctlr, rd->dn);
> >                 put_device(&ctlr->dev);
> >
> > --
> > 2.34.1
> >