linux-kernel - Re: [PATCH v2] i2c: spacemit: fix detect issue

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Message-ID: <5b1fd3ee-474f-48b7-8709-d07000a9a113@rootcommit.com>
Date: Thu, 13 Nov 2025 15:37:32 +0000 (UTC)
From: Michael Opdenacker <michael.opdenacker@...tcommit.com>
To: Troy Mitchell <troy.mitchell@...ux.spacemit.com>,
 Andi Shyti <andi.shyti@...nel.org>, Yixun Lan <dlan@...too.org>,
 Alex Elder <elder@...cstar.com>, Aurelien Jarno <aurelien@...el32.net>
Cc: 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 v2] i2c: spacemit: fix detect issue

Hi Troy

Thanks for the fix!

On 11/13/25 14:21, Troy Mitchell wrote:
> This commit addresses two issues causing i2c detect to fail.
>
> The identified issues are:
>
> 1. Incorrect error handling for BED (Bus Error No ACK/NAK):
>     Before this commit, Both ALD (Arbitration Loss Detected) and
>     BED returned -EAGAIN.
> 2. Missing interrupt status clear after initialization in xfer():
>     On the K1 SoC, simply fixing the first issue changed the error
>     from -EAGAIN to -ETIMEOUT. Through tracing, it was determined that
>     this is likely due to MSD (Master Stop Detected) latency issues.
>
>     That means the MSD bit in the ISR may still be set on the next transfer.
>     As a result, the controller won't work — we can see from the scope that
>     it doesn't issue any signal.
>     (This only occurs during rapid consecutive I2C transfers.
>     That explains why the issue only shows up with i2cdetect.)
>
> With these two fixes, i2c device detection now functions correctly on the K1 SoC.
>
> Fixes: 5ea558473fa31 ("i2c: spacemit: add support for SpacemiT K1 SoC")
> Tested-by: Aurelien Jarno <aurelien@...el32.net>
> Signed-off-by: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
> ---
> Changelog in v2:
> - handle ALD and BED errors separately in spacemit_i2c_handle_err()
> - move clear_int_status() above spacemit_i2c_init()
> - move clear_int_status() from xfer() into spacemit_i2c_init()
> - Link to v1: https://lore.kernel.org/all/20251103-fix-k1-detect-failure-v1-1-bb07a8d7de7c@linux.spacemit.com/
> ---
>   drivers/i2c/busses/i2c-k1.c | 19 +++++++++++++------
>   1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-k1.c b/drivers/i2c/busses/i2c-k1.c
> index 6b918770e612e098b8ad17418f420d87c94df166..d42c03ef5db5984ea8e06b3d7eb485b4f899e616 100644
> --- a/drivers/i2c/busses/i2c-k1.c
> +++ b/drivers/i2c/busses/i2c-k1.c
> @@ -158,11 +158,16 @@ static int spacemit_i2c_handle_err(struct spacemit_i2c_dev *i2c)
>   {
>   	dev_dbg(i2c->dev, "i2c error status: 0x%08x\n", i2c->status);
>   
> -	if (i2c->status & (SPACEMIT_SR_BED | SPACEMIT_SR_ALD)) {
> +	/* 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);
> +
>   	return i2c->status & SPACEMIT_SR_ACKNAK ? -ENXIO : -EIO;
>   }
>   
> @@ -224,6 +229,12 @@ static void spacemit_i2c_check_bus_release(struct spacemit_i2c_dev *i2c)
>   	}
>   }
>   
> +static inline void
> +spacemit_i2c_clear_int_status(struct spacemit_i2c_dev *i2c, u32 mask)
> +{
> +	writel(mask & SPACEMIT_I2C_INT_STATUS_MASK, i2c->base + SPACEMIT_ISR);
> +}
> +
>   static void spacemit_i2c_init(struct spacemit_i2c_dev *i2c)
>   {
>   	u32 val;
> @@ -267,12 +278,8 @@ static void spacemit_i2c_init(struct spacemit_i2c_dev *i2c)
>   	val = readl(i2c->base + SPACEMIT_IRCR);
>   	val |= SPACEMIT_RCR_SDA_GLITCH_NOFIX;
>   	writel(val, i2c->base + SPACEMIT_IRCR);
> -}
>   
> -static inline void
> -spacemit_i2c_clear_int_status(struct spacemit_i2c_dev *i2c, u32 mask)
> -{
> -	writel(mask & SPACEMIT_I2C_INT_STATUS_MASK, i2c->base + SPACEMIT_ISR);
> +	spacemit_i2c_clear_int_status(i2c, SPACEMIT_I2C_INT_STATUS_MASK);
>   }
>   
>   static void spacemit_i2c_start(struct spacemit_i2c_dev *i2c)
>
> ---
> base-commit: 6fa9041b7177f6771817b95e83f6df17b147c8c6
> change-id: 20251113-fix-k1-detect-failure-63483e45168b

Tested successfully on OrangePi RV2.

Tested-by: Michael Opdenacker <michael.opdenacker@...tcommit.com>
Thanks again
Michael.

-- 
Michael Opdenacker
Root Commit
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