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From: Kalle Valo <kvalo@kernel.org>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: Karthikeyan Periyasamy <quic_periyasa@quicinc.com>,
  ath12k@lists.infradead.org,  linux-wireless@vger.kernel.org
Subject: Re: [PATCH v2 3/3] wifi: ath12k: Add lock to protect the hardware
 state
References: <20240424065646.1666166-1-quic_periyasa@quicinc.com>
	<20240424065646.1666166-4-quic_periyasa@quicinc.com>
	<517caf852d37b3803bcf087a6b575f2ecdb5ba10.camel@sipsolutions.net>
Date: Wed, 24 Apr 2024 12:39:21 +0300
In-Reply-To: <517caf852d37b3803bcf087a6b575f2ecdb5ba10.camel@sipsolutions.net>
	(Johannes Berg's message of "Wed, 24 Apr 2024 09:28:20 +0200")
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Johannes Berg <johannes@sipsolutions.net> writes:

> On Wed, 2024-04-24 at 12:26 +0530, Karthikeyan Periyasamy wrote:
>> Currently, hardware state is not protected across the reconfigure
>> operations. However, in single wiphy models, multiple radio/links is
>> exposed as a MAC hardware (ieee80211_hw) through the driver hardware
>> abstraction (ath12k_hw) layer. In such scenario, we need to protect
>> hardware state across the multiple radio/link at the driver hardware
>> abstraction (ath12k_hw) layer. Therefore, introduce a new mutex in
>> the ath12k_hw layer.
>> 
>
> It's your driver, but ... it would seem _simpler_ to do locking across
> the hw with a single wiphy model, because everything (except currently
> for ath12k_core_reset and ath12k_core_restart) already holds the wiphy
> mutex. You can probably move those to wiphy work.
>
> I'd avoid doing lock explosion like we had in mac80211, it's going to
> come back and bite you eventually :)

Exactly. Swithing to use wiphy_lock() definitely one of my longterm
goals in ath12k. I already started working on switching ath12k to use
wiphy_lock() but IIRC I got blocked by not being able to call
wiphy_delayed_work_cancel() without taking wiphy_lock. One way to solve
that might be to convert WMI event handling to use wiphy work but didn't
have the time to work on that so I put it on the backborner. I should
resurrect that branch and submit it as RFC.

But for the time being I think we need to add another mutex to ath12k, I
don't want to block Karthikeyan for too long.

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