Re: [PATCH 3/4] thunderbolt: Fix adapter init handling during switch add

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Hi,

On Tue, Aug 03, 2021 at 12:23:44AM +0530, Sanjay R Mehta wrote:
> 
> 
> On 8/2/2021 8:56 PM, Mika Westerberg wrote:
> > [CAUTION: External Email]
> > 
> > On Mon, Aug 02, 2021 at 07:58:19AM -0500, Sanjay R Mehta wrote:
> >> From: Sanjay R Mehta <sanju.mehta@amd.com>
> >>
> >> Adapter0 (Port0) is the control adapter on the AMD USB4 host router.
> >> As per USB4 spec in "Section 1.8", Control Adapters do not
> >> have an Adapter Configuration Space".
> >>
> >> The read requests on Adapter0 time's out and driver initialization fails.
> >>
> >> Hence Disabling the Adapter in case of read-request timeout and continuing
> >> the driver init.
> >>
> >> Signed-off-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>
> >> Signed-off-by: Sanjay R Mehta <sanju.mehta@amd.com>
> >> ---
> >>  drivers/thunderbolt/switch.c | 3 ++-
> >>  1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
> >> index 83b1ef3..effbfe4 100644
> >> --- a/drivers/thunderbolt/switch.c
> >> +++ b/drivers/thunderbolt/switch.c
> >> @@ -2747,8 +2747,9 @@ int tb_switch_add(struct tb_switch *sw)
> >>                       }
> >>                       ret = tb_init_port(&sw->ports[i]);
> >>                       if (ret) {
> >> +                             sw->ports[i].disabled = true;
> >>                               dev_err(&sw->dev, "failed to initialize port %d\n", i);
> >> -                             return ret;
> >> +                             continue;
> > 
> > Instead of this, would it work if we start the loop at 1? In case of the
> > control adapter (0) tb_port_init() does not do anything useful anyway
> > and it actually would simplify that function too if we get rid of the
> > special casing.
> > 
> Hi Mika,
> 
> If we start loop from 1, it will work for host router
> but this will skip port (0) on device router which may be valid port.

For device router adapter 0 is also contror adapter so I think we can
just skip it here unconditionally.