linux-kernel - Re: [PATCH 1/1] PCA9541: Increase I2C bus arbitration timeout

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Message-ID: <aIc68UkzN_l0gZ_D@shikoro>
Date: Mon, 28 Jul 2025 10:55:13 +0200
From: Wolfram Sang <wsa+renesas@...g-engineering.com>
To: Manikanta Guntupalli <manikanta.guntupalli@....com>
Cc: git@....com, michal.simek@....com, peda@...ntia.se,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	radhey.shyam.pandey@....com, srinivas.goud@....com,
	shubhrajyoti.datta@....com, manikantaguntupalli09@...il.com,
	Jonathan Stroud <jonathan.stroud@....com>
Subject: Re: [PATCH 1/1] PCA9541: Increase I2C bus arbitration timeout

Hi,

thanks for your patch.

>  /* arbitration timeouts, in jiffies */
> -#define ARB_TIMEOUT	(HZ / 8)	/* 125 ms until forcing bus ownership */
> -#define ARB2_TIMEOUT	(HZ / 4)	/* 250 ms until acquisition failure */
> +#define ARB_TIMEOUT	(HZ)		/* 1 s until forcing bus ownership */
> +#define ARB2_TIMEOUT	(2 * HZ)	/* 2 s until acquisition failure */

Can't we use the timeout value of the parent struct i2c_adapter? This is
by default HZ and can be set by userspace via IOCTL depending on the
actual use case. So, we would use (pseudo-code, probably):

254         unsigned long timeout = jiffies + 2 * client->adapter->timeout;
255                 /* give up after this time */
256 
257         data->arb_timeout = jiffies + client->adapter->timeout;

?


> +			dev_info(&client->dev, "I2C Bus Arbiter timeout, forcing take bus\n");

'dev_warn' for both?

Happy hacking,

   Wolfram


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