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

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Message-ID:
 <TYZPR03MB7001AA581B8B63AC19A7977C80B02@TYZPR03MB7001.apcprd03.prod.outlook.com>
Date: Tue, 30 Jul 2024 10:00:20 +0000
From: Jacobe Zang <jacobe.zang@...ion.com>
To: Arend Van Spriel <arend.vanspriel@...adcom.com>, Krzysztof Kozlowski
	<krzk@...nel.org>, "robh@...nel.org" <robh@...nel.org>, "krzk+dt@...nel.org"
	<krzk+dt@...nel.org>, "heiko@...ech.de" <heiko@...ech.de>, "kvalo@...nel.org"
	<kvalo@...nel.org>, "davem@...emloft.net" <davem@...emloft.net>,
	"edumazet@...gle.com" <edumazet@...gle.com>, "kuba@...nel.org"
	<kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>,
	"conor+dt@...nel.org" <conor+dt@...nel.org>, Linus Walleij
	<linus.walleij@...aro.org>
CC: "efectn@...tonmail.com" <efectn@...tonmail.com>, "dsimic@...jaro.org"
	<dsimic@...jaro.org>, "jagan@...eble.ai" <jagan@...eble.ai>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
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	<linux-rockchip@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "arend@...adcom.com" <arend@...adcom.com>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, "megi@....cz"
	<megi@....cz>, "duoming@....edu.cn" <duoming@....edu.cn>,
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>, "minipli@...ecurity.net"
	<minipli@...ecurity.net>, "brcm80211@...ts.linux.dev"
	<brcm80211@...ts.linux.dev>, "brcm80211-dev-list.pdl@...adcom.com"
	<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 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?

---
Best Regards
Jacobe