linux-kernel - Re: [PATCH] i2c: spacemit: fix detect issue

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Message-ID: <aQwzYrmv5TAIuqTh@aurel32.net>
Date: Thu, 6 Nov 2025 06:34:26 +0100
From: Aurelien Jarno <aurelien@...el32.net>
To: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
Cc: Andi Shyti <andi.shyti@...nel.org>, Yixun Lan <dlan@...too.org>,
	Alex Elder <elder@...cstar.com>,
	Michael Opdenacker <michael.opdenacker@...tcommit.com>,
	Troy Mitchell <troymitchell988@...il.com>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org, spacemit@...ts.linux.dev
Subject: Re: [PATCH] i2c: spacemit: fix detect issue

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. 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.

Regards
Aurelien

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@...el32.net                     http://aurel32.net