linux-kernel - Re: [PATCH v2] usb: typec: tipd: Don't block probing of consumer of "connector" nodes

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Message-ID: <CAGETcx-rfcP9dFSstf7PKmc2W3kWRLCMRGz8uCvJxo-OpFpjgw@mail.gmail.com>
Date:   Thu, 21 Jul 2022 16:06:15 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Martin Kepplinger <martin.kepplinger@...i.sm>
Cc:     grandmaster@...klimov.de, gregkh@...uxfoundation.org,
        heikki.krogerus@...ux.intel.com, rjw@...ysocki.net, kernel@...i.sm,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        Android Kernel Team <kernel-team@...roid.com>
Subject: Re: [PATCH v2] usb: typec: tipd: Don't block probing of consumer of
 "connector" nodes

On Tue, Jul 13, 2021 at 11:18 PM Martin Kepplinger
<martin.kepplinger@...i.sm> wrote:
>
> Similar as with tcpm this patch lets fw_devlink know not to wait on the
> fwnode to be populated as a struct device.
>
> Without this patch, USB functionality can be broken on some previously
> supported boards.
>
> Fixes: 28ec344bb891 ("usb: typec: tcpm: Don't block probing of consumers of "connector" nodes")
> Signed-off-by: Martin Kepplinger <martin.kepplinger@...i.sm>
> ---
>
> revision history
> ----------------
> v2: (thank you Saravana)
> * add a code-comment why the call is needed.
>
> v1:
> https://lore.kernel.org/linux-usb/20210713073946.102501-1-martin.kepplinger@puri.sm/
>
>
>
>  drivers/usb/typec/tipd/core.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/drivers/usb/typec/tipd/core.c b/drivers/usb/typec/tipd/core.c
> index 938219bc1b4b..21b3ae25c76d 100644
> --- a/drivers/usb/typec/tipd/core.c
> +++ b/drivers/usb/typec/tipd/core.c
> @@ -629,6 +629,15 @@ static int tps6598x_probe(struct i2c_client *client)
>         if (!fwnode)
>                 return -ENODEV;
>
> +       /*
> +        * This fwnode has a "compatible" property, but is never populated as a
> +        * struct device. Instead we simply parse it to read the properties.
> +        * This breaks fw_devlink=on. To maintain backward compatibility
> +        * with existing DT files, we work around this by deleting any
> +        * fwnode_links to/from this fwnode.
> +        */
> +       fw_devlink_purge_absent_suppliers(fwnode);
> +

Hey Martin,

As part of a series I'm working on, I'm looking into deleting
fw_devlink_purge_absent_suppliers() and having the driver core figure
this out automatically.

So I was making sure all the current uses of
fw_devlink_purge_absent_suppliers() would automatically be handled by
driver core. But when I looked at this usage of
fw_devlink_purge_absent_suppliers(), I didn't see any "compatible"
property in the "connector" child node. So, I'm confused how you had a
problem without this patch.

fw_devlink would have created fwnode links
between typec_pd and usb_dwc3_0, figured out it's a cycle and have
stopped enforcing the "remote-endpoint" dependencies.

Can you give me more details please on why you were having a problem
without this patch?

I'm looking at arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi as an
example because you listed it in your v1 patch.

-Saravana

>         tps->role_sw = fwnode_usb_role_switch_get(fwnode);
>         if (IS_ERR(tps->role_sw)) {
>                 ret = PTR_ERR(tps->role_sw);
> --
> 2.30.2
>