RE: [PATCH v2 1/1] ath10k: add option for chip-id based BDF selection

["Rakesh Pillai" <pillair@codeaurora.org>]

> -----Original Message-----
> From: Doug Anderson <dianders@chromium.org>
> Sent: Tuesday, December 1, 2020 12:49 AM
> To: Rakesh Pillai <pillair@codeaurora.org>
> Cc: Abhishek Kumar <kuabhs@chromium.org>; Kalle Valo
> <kvalo@codeaurora.org>; LKML <linux-kernel@vger.kernel.org>; ath10k
> <ath10k@lists.infradead.org>; Brian Norris <briannorris@chromium.org>;
> linux-wireless <linux-wireless@vger.kernel.org>; David S. Miller
> <davem@davemloft.net>; Jakub Kicinski <kuba@kernel.org>; netdev
> <netdev@vger.kernel.org>
> Subject: Re: [PATCH v2 1/1] ath10k: add option for chip-id based BDF
> selection
> 
> Hi,
> 
> On Tue, Nov 24, 2020 at 7:44 PM Rakesh Pillai <pillair@codeaurora.org>
> wrote:
> >
> > > > I missed on reviewing this change. Also I agree with Doug that this is not
> > > the change I was looking for.
> > > >
> > > > The argument "with_variant" can be renamed to "with_extra_params".
> > > There is no need for any new argument to this function.
> > > > Case 1: with_extra_params=0,  ar->id.bdf_ext[0] = 0             ->   The
> default
> > > name will be used (bus=snoc,qmi_board_id=0xab)
> > > > Case 2: with_extra_params=1,  ar->id.bdf_ext[0] = 0             ->
> > > bus=snoc,qmi_board_id=0xab,qmi_chip_id=0xcd
> > > > Case 3: with_extra_params=1,  ar->id.bdf_ext[0] = "xyz"      ->
> > > bus=snoc,qmi_board_id=0xab,qmi_chip_id=0xcd,variant=xyz
> > > >
> > > > ar->id.bdf_ext[0] depends on the DT entry for variant field.
> > >
> > > I'm confused about your suggestion.  Maybe you can help clarify.  Are
> > > you suggesting:
> > >
> > > a) Only two calls to ath10k_core_create_board_name()
> > >
> > > I'm pretty sure this will fail in some cases.  Specifically consider
> > > the case where the device tree has a "variant" defined but the BRD
> > > file only has one entry for (board-id) and one for (board-id +
> > > chip-id) but no entry for (board-id + chip-id + variant).  If you are
> > > only making two calls then I don't think you'll pick the right one.
> > >
> > > Said another way...
> > >
> > > If the device tree has a variant:
> > > 1. We should prefer a BRD entry that has board-id + chip-id + variant
> > > 2. If #1 isn't there, we should prefer a BRD entry that has board-id + chip-
> id
> > > 3. If #1 and #2 aren't there we fall back to a BRD entry that has board-id.
> > >
> > > ...without 3 calls to ath10k_core_create_board_name() we can't handle
> > > all 3 cases.
> >
> > This can be handled by two calls to ath10k_core_create_board_name
> > 1) ath10k_core_create_board_name(ar, boardname, sizeof(boardname),
> true)   :  As per my suggestions, this can result in two possible board names
> >     a) If DT have the "variant" node, it outputs the #1 from your suggestion
> (1. We should prefer a BRD entry that has board-id + chip-id + variant)
> >     b) If DT does not have the "variant" node, it outputs the #2 from your
> suggestion (2. If #1 isn't there, we should prefer a BRD entry that has board-
> id + chip-id)
> >
> > 2) ath10k_core_create_board_name(ar, boardname, sizeof(boardname),
> false)    :  This is the second call to this function and outputs the #3 from your
> suggestion (3. If #1 and #2 aren't there we fall back to a BRD entry that has
> board-id)
> 
> What I'm trying to say is this.  Imagine that:
> 
> a) the device tree has the "variant" property.
> 
> b) the BRD file has two entries, one for "board-id" (1) and one for
> "board-id + chip-id" (2).  It doesn't have one for "board-id + chip-id
> + variant" (3).
> 
> With your suggestion we'll see the "variant" property in the device
> tree.  That means we'll search for (1) and (3).  (3) isn't there, so
> we'll pick (1).  ...but we really should have picked (2), right?


Do we expect board-2.bin to not be populated with the bdf with variant field (if its necessary ?)
Seems fine for me, if we have 2 fallback names if that is needed.

> 
> -Doug