netdev - Re: [PATCH v5 2/5] dt-bindings: net: wireless: brcm4329-fmac: add clock description for AP6275P

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Message-ID: <191031cb638.279b.9b12b7fc0a3841636cfb5e919b41b954@broadcom.com>
Date: Tue, 30 Jul 2024 12:08:19 +0200
From: Arend Van Spriel <arend.vanspriel@...adcom.com>
To: Jacobe Zang <jacobe.zang@...ion.com>, Krzysztof Kozlowski <krzk@...nel.org>, <robh@...nel.org>, <krzk+dt@...nel.org>, <heiko@...ech.de>, <kvalo@...nel.org>, <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>, <conor+dt@...nel.org>, Linus Walleij <linus.walleij@...aro.org>
CC: <efectn@...tonmail.com>, <dsimic@...jaro.org>, <jagan@...eble.ai>, <devicetree@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>, <linux-rockchip@...ts.infradead.org>, <linux-kernel@...r.kernel.org>, <arend@...adcom.com>, <linux-wireless@...r.kernel.org>, <netdev@...r.kernel.org>, <megi@....cz>, <duoming@....edu.cn>, <bhelgaas@...gle.com>, <minipli@...ecurity.net>, <brcm80211@...ts.linux.dev>, <brcm80211-dev-list.pdl@...adcom.com>, Nick Xie <nick@...das.com>
Subject: Re: [PATCH v5 2/5] dt-bindings: net: wireless: brcm4329-fmac: add clock description for AP6275P

On July 30, 2024 12:00:25 PM Jacobe Zang <jacobe.zang@...ion.com> wrote:

>>> On 30/07/2024 08:37, Arend Van Spriel wrote:
>>>> + Linus W
>>>>
>>>> On July 30, 2024 5:31:15 AM Jacobe Zang <jacobe.zang@...ion.com> wrote:
>>>>
>>>>> Not only AP6275P Wi-Fi device but also all Broadcom wireless devices allow
>>>>> external low power clock input. In DTS the clock as an optional choice in
>>>>> the absence of an internal clock.
>>>>>
>>>>> Reviewed-by: Arend van Spriel <arend.vanspriel@...adcom.com>
>>>>> Signed-off-by: Jacobe Zang <jacobe.zang@...ion.com>
>>>>> ---
>>>>> .../bindings/net/wireless/brcm,bcm4329-fmac.yaml          | 8 ++++++++
>>>>> 1 file changed, 8 insertions(+)
>>>>>
>>>>> diff --git
>>>>> a/Documentation/devicetree/bindings/net/wireless/brcm,bcm4329-fmac.yaml
>>>>> b/Documentation/devicetree/bindings/net/wireless/brcm,bcm4329-fmac.yaml
>>>>> index 2c2093c77ec9a..a3607d55ef367 100644
>>>>> --- a/Documentation/devicetree/bindings/net/wireless/brcm,bcm4329-fmac.yaml
>>>>> +++ b/Documentation/devicetree/bindings/net/wireless/brcm,bcm4329-fmac.yaml
>>>>> @@ -122,6 +122,14 @@ properties:
>>>>> NVRAM. This would normally be filled in by the bootloader from platform
>>>>> configuration data.
>>>>>
>>>>> +  clocks:
>>>>> +    items:
>>>>> +      - description: External Low Power Clock input (32.768KHz)
>>>>> +
>>>>> +  clock-names:
>>>>> +    items:
>>>>> +      - const: lpo
>>>>> +
>>>>
>>>> We still have an issue that this clock input is also present in the
>>>> bindings specification broadcom-bluetooth.yaml (not in bluetooth
>>>> subfolder). This clock is actually a chip resource. What happens if both
>>>> are defined and both wifi and bt drivers try to enable this clock? Can this
>>>> be expressed in yaml or can we only put a textual warning in the property
>>>> descriptions?
>>>
>>> Just like all clocks, what would happen? It will be enabled.
>>
>> Oh, wow! Cool stuff. But seriously is it not a problem to have two entities
>> controlling one and the same clock? Is this use-case taken into account by
>> the clock framework?
>
> I have enabled the same clock both in bluetooth and wifi just now, they worked
> well. Maybe this make sense?

What happens if you unload one of the drivers? Also would like to know if 
you are using an nvram file. If so can you share it's content.

Regards,
Arend