Re: [PATCH] i2c: spacemit: fix detect issue

From: Aurelien Jarno <aurelien@aurel32.net>
To: Troy Mitchell <troy.mitchell@linux.spacemit.com>
Cc: Andi Shyti <andi.shyti@kernel.org>, Yixun Lan <dlan@gentoo.org>,
	Alex Elder <elder@riscstar.com>,
	Michael Opdenacker <michael.opdenacker@rootcommit.com>,
	Troy Mitchell <troymitchell988@gmail.com>,
	linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-riscv@lists.infradead.org, spacemit@lists.linux.dev
Subject: Re: [PATCH] i2c: spacemit: fix detect issue
Date: Thu, 6 Nov 2025 19:17:00 +0100	[thread overview]
Message-ID: <aQzmHB2FaPFS4qwj@aurel32.net> (raw)
In-Reply-To: <0E2B2679F0650AE1+aQw0VgKNbcFqDH33@kernel.org>

Hi,

On 2025-11-06 13:38, Troy Mitchell wrote:
> On Thu, Nov 06, 2025 at 06:34:26AM +0100, Aurelien Jarno wrote:
> > Hi,
> > 
> > On 2025-11-06 09:05, Troy Mitchell wrote:
> > > On Wed, Nov 05, 2025 at 11:44:00PM +0100, Aurelien Jarno wrote:
> > > > Hi,
> > > > 
> > > > On 2025-11-03 15:06, Troy Mitchell wrote:
> > > [...]
> > > > >  	if (i2c->status & (SPACEMIT_SR_BED | SPACEMIT_SR_ALD)) {
> > > > >  		spacemit_i2c_reset(i2c);
> > > > > -		return -EAGAIN;
> > > > > +		if (i2c->status & SPACEMIT_SR_ALD)
> > > > > +			return -EAGAIN;
> > > > >  	}
> > > > 
> > > > This makes the resulting code, while correct, complex to understand as 
> > > > it is now two really different errors, as you explained well in the 
> > > > commit message.
> > > > 
> > > > I therefore suggest to organize the code as:
> > > > 
> > > > 	/* Arbitration Loss Detected */
> > > > 	if (i2c->status & SPACEMIT_SR_ALD) {
> > > > 		spacemit_i2c_reset(i2c);
> > > > 		return -EAGAIN;
> > > > 	}
> > > > 
> > > > 	/* Bus Error No ACK/NAK */
> > > > 	if (i2c->status & SPACEMIT_SR_BED) {
> > > > 		spacemit_i2c_reset(i2c);
> > > > 	}
> > > Thanks. I'll fix it in the next version.
> > > > 
> > > > 
> > > > >  	return i2c->status & SPACEMIT_SR_ACKNAK ? -ENXIO : -EIO;
> > > > > @@ -491,6 +492,8 @@ static int spacemit_i2c_xfer(struct i2c_adapter *adapt, struct i2c_msg *msgs, in
> > > > >  
> > > > >  	spacemit_i2c_init(i2c);
> > > > >  
> > > > > +	spacemit_i2c_clear_int_status(i2c, SPACEMIT_I2C_INT_STATUS_MASK);
> > > > > +
> > > > 
> > > > This sounds good to start the transfer with a clean interrupt state. I 
> > > > just wonder if it should be moved to spacemit_i2c_init(), ie where the 
> > > > corresponding interrupts are enabled.
> > > Uh, We can move it actually. But is it essentail?
> > 
> > For me ensuring that the interrupt status is in a clean state after 
> > enabling the interrupt is part of the initialization.
> Yes, I agree that.
> > Furthermore if 
> > spacemit_i2c_init() has to be called from another place, it's very 
> > likely that it's also needed to get interrupt status in a clean state.
> Why we need to call init() in other place?
> Could you give me a cese?

Currently there is no need to do that. However if the driver is extended 
(e.g. to add new features) and spacemit_i2c_init() needs to be called 
from another place, it is likely that a reset of the interrupt status 
should also be included. Therefore it's better to just include it 
directly in spacemit_i2c_init().

Regards
Aurelien

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                     http://aurel32.net