On 06/19/15 20:49, Rob Herring wrote:
On Fri, Jun 19, 2015 at 12:06 PM, Arend van Spriel<arend@xxxxxxxxxxxx> wrote:
On 06/19/15 17:47, Rob Herring wrote:
On Thu, Jun 18, 2015 at 3:37 PM, Ilya Faenson<ifaenson@xxxxxxxxxxxx>
wrote:
Hi Rob.
-----Original Message-----
From: linux-bluetooth-owner@xxxxxxxxxxxxxxx
[mailto:linux-bluetooth-owner@xxxxxxxxxxxxxxx] On Behalf Of Rob Herring
Sent: Thursday, June 18, 2015 3:41 PM
To: Ilya Faenson
Cc: marcel@xxxxxxxxxxxx; Arend Van Spriel; devicetree@xxxxxxxxxxxxxxx;
linux-bluetooth@xxxxxxxxxxxxxxx
Subject: Re: FW: [PATCH v4 1/4] Broadcom Bluetooth UART Device Tree
bindings
On Thu, Jun 18, 2015 at 1:54 PM, Ilya Faenson<ifaenson@xxxxxxxxxxxx>
wrote:
Hi Rob,
Your emails are base64 encoded. They should be plain text for the list.
IF: The Outlook is configured to respond in the sender's format. I
therefore respond in the encoding you've used.
I assure you that that is not the case or I would be banished from
lists by now. Outlook is generally incapable of correctly sending
mails to lists. The reply header above is one aspect of that. The
other problem is your replies don't get wrapped and prefixed properly.
That could be my client I guess, but *all* other mails are fine.
My sent mails have:
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
-----Original Message-----
From: Rob Herring [mailto:robherring2@xxxxxxxxx]
Sent: Thursday, June 18, 2015 11:03 AM
To: Ilya Faenson
Cc: marcel@xxxxxxxxxxxx; Arend Van Spriel; devicetree@xxxxxxxxxxxxxxx;
linux-bluetooth@xxxxxxxxxxxxxxx
Subject: Re: FW: [PATCH v4 1/4] Broadcom Bluetooth UART Device Tree
bindings
On Wed, Jun 17, 2015 at 6:11 PM, Ilya Faenson<ifaenson@xxxxxxxxxxxx>
wrote:
+ devicetree lists
[...]
diff --git a/Documentation/devicetree/bindings/net/bluetooth/btbcm.txt
b/Documentation/devicetree/bindings/net/bluetooth/btbcm.txt
new file mode 100644
index 0000000..5dbcd57
--- /dev/null
+++ b/Documentation/devicetree/bindings/net/bluetooth/btbcm.txt
@@ -0,0 +1,86 @@
+btbcm
+------
+
+Required properties:
+
+ - compatible : must be "brcm,brcm-bt-uart".
You need to describe the chip, not the interface.
IF: This driver is for all Broadcom Bluetooth UART based chips.
BT only chips? Most/many Broadcom chips are combo chips. I understand
the driver for BT is *mostly* separate from other chip functions like
WiFi, GPS and NFC, but the h/w is a single chip. I say most because
likely there are some parts shared: a voltage rail, reset line, or
power down line. I think some can do BT over the SDIO interface too,
so the interface may be shared. The DT is a description of the h/w
(i.e. what part # for a chip) and not a driver data structure. You
need to describe the whole chip in the binding. It is a Linux problem
if there needs to be multiple separate drivers.
IF: Defining complete DT description for the Broadcom combo chips for
multiple interfaces is well beyond the scope of what I am doing. I just need
to define a DT node for the input and output GPIOs connected to the BT UART
chip. BT may or may not be part of the combo chip: it does not really matter
for this exercise. I thought I would take this opportunity to place some BT
device parameters into that node as well. If you're not comfortable with
this, I could just call it a "GPIO set" to avoid mentioning BT and UART at
all but it would make little sense. Still, I could consider it. Would you
have "GPIO set" recommendations? Alternatively, NFC Marvell code you're
referring to has parameters configured as Linux module parameters. I could
do the same too, avoiding this device tree discussion. Let me know.
I don't completely follow what you mean by "GPIO set", but I'm
guessing that is not the right path.
Generally speaking (pontification hat on :-)), what you're trying to do
(description of the whole chip) is well beyond what say ACPI has done (I was
involved some in the BT ACPI exercise a few years ago). BT UART interface is
described in ACPI independently of other parts of the same combo chip.
Requirements like that slow down the DT development in my opinion as
companies are understandably reluctant to work with unrealistic goals. End
of pontification. :-)
ACPI and DT are very different models in terms of abstraction and
governance. I'm not going to hash through all the details.
I'm not necessarily saying we have to have a single node, but that is
my default position. You have convince me that the functions are
completely independent and I cannot judge that if you are completely
ignoring the WiFi part. From Broadcom chips I've worked with, the
supplies at least are shared (something ACPI does not expose). Perhaps
we could fudge that and just require the same supply has to be
connected to each half. I still worry there could be other internal
inter-dependencies. Perhaps BT requires the SDIO clock to be active or
something like that. Maybe not on Broadcom chips, but on other vendors
and I have to care about them all.
All Broadcom combo chips that I know of have separate supplies, ie.
wl-reg-on and bt-reg-on. There already is a binding present for the wifi
GPIOs are not supplies. For the module I'm working with (43340 based)
there is a single VDDIO and VBAT supplies which are shared. Now
whether the module or the chip are tying things together, I don't
know. There is also a 32kHz clock input. Is that part of WiFi or BT?
True and I see where you are going here. The 32kHz clock is input for
low-power oscillator in the chip. That LPO provides clock for the
interconnect in the chip so it is not part of wifi nor bt.
part. Not extending that may seem ignorant, but as wifi and bt can have a
separate interface to the host (admittedly they could share SDIO interface,
but they would be exposed as a separate SDIO function) I did not see a
reason to object against a separate binding for BT. Whether wifi and bt are
on the same device does not seem like something that must be expressed in
DT. The physical state may help in determining DT bindings, but it should
not be mandatory in my opinion.
We don't need it in DT until we do. Soon as there is some some
interdependence, something in DT will be needed.
Agree.
Regards,
Arend
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