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SubjectRe: [PATCH v3 2/5] i3c: master: make sure ->boardinfo is initialized in add_i3c_dev_locked()
On Thu, 3 Oct 2019 17:37:40 +0000
Vitor Soares <Vitor.Soares@synopsys.com> wrote:

> Hi Boris,
>
> From: Boris Brezillon <boris.brezillon@collabora.com>
> Date: Thu, Oct 03, 2019 at 15:29:43
>
> > On Thu, 5 Sep 2019 12:00:35 +0200
> > Vitor Soares <Vitor.Soares@synopsys.com> wrote:
> >
> > > The newdev->boardinfo assignment was missing in
> > > i3c_master_add_i3c_dev_locked() and hence the ->of_node info isn't
> > > propagated to i3c_dev_desc.
> > >
> > > Fix this by trying to initialize device i3c_dev_boardinfo if available.
> > >
> > > Cc: <stable@vger.kernel.org>
> > > Fixes: 3a379bbcea0a ("i3c: Add core I3C infrastructure")
> > > Signed-off-by: Vitor Soares <vitor.soares@synopsys.com>
> > > ---
> > > Change in v3:
> > > - None
> > >
> > > Changes in v2:
> > > - Change commit message
> > > - Change i3c_master_search_i3c_boardinfo(newdev) to
> > > i3c_master_init_i3c_dev_boardinfo(newdev)
> > > - Add fixes, stable tags
> > >
> > > /**
> > > * i3c_master_add_i3c_dev_locked() - add an I3C slave to the bus
> > > * @master: master used to send frames on the bus
> > > @@ -1818,8 +1834,9 @@ int i3c_master_add_i3c_dev_locked(struct i3c_master_controller *master,
> > > u8 addr)
> > > {
> > > struct i3c_device_info info = { .dyn_addr = addr };
> > > - struct i3c_dev_desc *newdev, *olddev;
> > > u8 old_dyn_addr = addr, expected_dyn_addr;
> > > + enum i3c_addr_slot_status addrstatus;
> > > + struct i3c_dev_desc *newdev, *olddev;
> > > struct i3c_ibi_setup ibireq = { };
> > > bool enable_ibi = false;
> > > int ret;
> > > @@ -1878,6 +1895,8 @@ int i3c_master_add_i3c_dev_locked(struct i3c_master_controller *master,
> > > if (ret)
> > > goto err_detach_dev;
> > >
> > > + i3c_master_init_i3c_dev_boardinfo(newdev);
> > > +
> > > /*
> > > * Depending on our previous state, the expected dynamic address might
> > > * differ:
> > > @@ -1895,7 +1914,11 @@ int i3c_master_add_i3c_dev_locked(struct i3c_master_controller *master,
> > > else
> > > expected_dyn_addr = newdev->info.dyn_addr;
> > >
> > > - if (newdev->info.dyn_addr != expected_dyn_addr) {
> > > + addrstatus = i3c_bus_get_addr_slot_status(&master->bus,
> > > + expected_dyn_addr);
> > > +
> > > + if (newdev->info.dyn_addr != expected_dyn_addr &&
> > > + addrstatus == I3C_ADDR_SLOT_FREE) {
> >
> > First, this change shouldn't be part of this patch, since the commit
> > message only mentions the boardinfo init stuff,
>
> This is not an issue, I can create a patch just for boardinfo init fix.
>
> > not the extra 'is slot
> > free check'.
>
> Even ignoring patch 1, it is necessary to check if the slot is free
> because if SETDASA fails the boardinfo->init_dyn_addr can be assigned to
> another device. That's why we need to check if expected_dyn_addr is free.

Correct. I thought we were already pre-reserving the init_addr (as
described here [1]), but it looks like the code is buggy. That's
probably something we should fix (we should reserve ->init_i3c_addr
here [2], not ->dyn_addr).

>
> > Plus, I want the fix to be backported so we should avoid
> > any unneeded deps.
> >
> > But even with those 2 things addressed, I'm still convinced the
> > 'free desc when device is not reachable' change you do in patch 1 is
> > not that great,
>
> If I'm doing wrong I really appreciate you tell me the reason.

I just think it's easier to keep track of things (like reserved
addresses) if the descriptor stays around even if the device is not yet
accessible.

>
> > and the fact that you can't pre-reserve the address to
> > make sure no one uses it until the device had a chance to show up tends
> > to prove me right.
>
> This is a different corner case and I though we agreed that the framework
> doesn't provide guarantees to assign boardinfo->init_dyn_addr [1].

Well, it doesn't, but we should try hard to not use addresses that
have been requested by a device.

>
> Yet, I don't disagree with the idea of pre-reserve the
> boardinfo->init_dyn_addr.
> I can do this but we need to align how it should be done.

Keep the device around even if SETDASA fails and make sure the
->init_dyn_addr is reserved. It's how it was supposed to work, there's
just a bug in the logic.
>
> >
> > Can we please do what I suggest and solve the "not enough dev slots"
> > problem later on (if we really have to).
>
> I have this use case where the HC has only 4 slot for 4 devices.
> Sometimes the one or more devices can be sleeping and when they trigger
> HJ there is no space in HC.

Let's address that separately please. I want to solve one problem at a
time.

[1]https://elixir.bootlin.com/linux/latest/source/drivers/i3c/master.c#L1330
[2]https://elixir.bootlin.com/linux/latest/source/drivers/i3c/master.c#L1307

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