linux-kernel - Re: [PATCH] i3c: dw: Disable IBI IRQ depends on hot-join and SIR enabling

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Message-ID: <645d4f645b1296d54573c4fe734768adab160035.camel@codeconstruct.com.au>
Date: Mon, 06 May 2024 13:09:35 +0800
From: Jeremy Kerr <jk@...econstruct.com.au>
To: Dylan Hung <dylan_hung@...eedtech.com>, "alexandre.belloni@...tlin.com"
 <alexandre.belloni@...tlin.com>, "joel@....id.au" <joel@....id.au>, 
 "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
 "gustavoars@...nel.org" <gustavoars@...nel.org>,
 "krzysztof.kozlowski@...aro.org" <krzysztof.kozlowski@...aro.org>,
 "zenghuchen@...gle.com" <zenghuchen@...gle.com>,
 "matt@...econstruct.com.au" <matt@...econstruct.com.au>, 
 "linux-i3c@...ts.infradead.org" <linux-i3c@...ts.infradead.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc: BMC-SW <BMC-SW@...eedtech.com>
Subject: Re: [PATCH] i3c: dw: Disable IBI IRQ depends on hot-join and SIR
 enabling

Hi Dylan,

Thanks for the response! I have a couple of follow-up things though:

> > My interpretation of this change is that we keep the "global" IBI irq enabled if
> > hot-join-nack is set (ie, always, because we don't support hot join, and
> > configure the hardware to nack all hot join requests).
> > 
> I would like to clarify the control logic, incorporating the principle
> of disabling the SIR interrupt signal:
> 
> Case 1:
> When `DEV_CTRL_HOT_JOIN_NACK` is set, indicating `hj_rejected` is
> true, it signifies the controller's non-receptiveness to the hot-join
> event. Consequently, we can safely disable the SIR interrupt signal if
> none of the target devices request SIR (reg == 0xffffffff).
> 
> Case 2:
> When `DEV_CTRL_HOT_JOIN_NACK` is unset, indicating `hj_rejected` is
> false, this indicates the controller's readiness to engage with the
> hot-join event. Therefore, it's imperative to keep the SIR interrupt
> signal enabled, even if not all target devices request SIR. In this
> case, `global` is false and `enable` is false.

Yep, I see what you're doing there, but it looks like the correct state
would never be set if we're not enabling/disabling the IBIs separately;
with this code, we would only ever enable the SIR for the HJ if we
*also* happen to enable IBIs.

The initial state would be to have all SIRs masked.

> Billy recently submitted a change to implement the hot-join enabling/disabling. Therefore, it is timely to consider the hot-join functionality.
> https://patchwork.kernel.org/project/linux-i3c/patch/20240429073624.256830-1-billy_tsai@aspeedtech.com/

Yep, I saw that, excellent! It's next on my list to take a look at.

It's just a little unusual that we're enabling the HJ interrupt before
actually having the HJ support though.

Cheers,


Jeremy