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From: Wolfram Sang <wsa@kernel.org>
To: "Ivan T. Ivanov" <iivanov@suse.de>
Cc: Florian Fainelli <f.fainelli@gmail.com>,
	Ray Jui <rjui@broadcom.com>,
	Scott Branden <sbranden@broadcom.com>,
	Nicolas Saenz Julienne <nsaenz@kernel.org>,
	linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	Phil Elwell <phil@raspberrypi.org>
Subject: Re: [PATCH] i2c: bcm2835: Set clock-stretch timeout to 35ms
Date: Fri, 28 Jan 2022 11:37:31 +0100	[thread overview]
Message-ID: <YfPHawUXJRPDHPmM@shikoro> (raw)
In-Reply-To: <20220117102504.90585-1-iivanov@suse.de>

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Hi Ivan,

> The BCM2835 I2C blocks have a register to set the clock-stretch
> timeout - how long the device is allowed to hold SCL low - in bus
> cycles. The current driver doesn't write to the register, therefore
> the default value of 64 cycles is being used for all devices.
> 
> Set the timeout to the value recommended for SMBus - 35ms.

By default, busses are I2C and not SMBus, so it looks like we should
finally apply this patch which disables CLKT:

http://patchwork.ozlabs.org/project/linux-i2c/patch/1519422151-6218-1-git-send-email-stefan.wahren@i2se.com/

If you really want the SMBus timeout applied, you can check for a
"smbus" property in DT and then set CLKT accordingly in a seperate
patch.

Kind regards,

   Wolfram


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WARNING: multiple messages have this Message-ID (diff)
From: Wolfram Sang <wsa@kernel.org>
To: "Ivan T. Ivanov" <iivanov@suse.de>
Cc: Florian Fainelli <f.fainelli@gmail.com>,
	Ray Jui <rjui@broadcom.com>,
	Scott Branden <sbranden@broadcom.com>,
	Nicolas Saenz Julienne <nsaenz@kernel.org>,
	linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	Phil Elwell <phil@raspberrypi.org>
Subject: Re: [PATCH] i2c: bcm2835: Set clock-stretch timeout to 35ms
Date: Fri, 28 Jan 2022 11:37:31 +0100	[thread overview]
Message-ID: <YfPHawUXJRPDHPmM@shikoro> (raw)
In-Reply-To: <20220117102504.90585-1-iivanov@suse.de>


[-- Attachment #1.1: Type: text/plain, Size: 759 bytes --]

Hi Ivan,

> The BCM2835 I2C blocks have a register to set the clock-stretch
> timeout - how long the device is allowed to hold SCL low - in bus
> cycles. The current driver doesn't write to the register, therefore
> the default value of 64 cycles is being used for all devices.
> 
> Set the timeout to the value recommended for SMBus - 35ms.

By default, busses are I2C and not SMBus, so it looks like we should
finally apply this patch which disables CLKT:

http://patchwork.ozlabs.org/project/linux-i2c/patch/1519422151-6218-1-git-send-email-stefan.wahren@i2se.com/

If you really want the SMBus timeout applied, you can check for a
"smbus" property in DT and then set CLKT accordingly in a seperate
patch.

Kind regards,

   Wolfram


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  parent reply	other threads:[~2022-01-28 10:37 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-17 10:25 [PATCH] i2c: bcm2835: Set clock-stretch timeout to 35ms Ivan T. Ivanov
2022-01-17 10:25 ` Ivan T. Ivanov
2022-01-28  8:47 ` Ivan T . Ivanov
2022-01-28  8:47   ` Ivan T . Ivanov
2022-01-28 10:37 ` Wolfram Sang [this message]
2022-01-28 10:37   ` Wolfram Sang
2022-02-07 15:15   ` Wolfram Sang
2022-02-07 15:15     ` Wolfram Sang
2022-02-07 15:41     ` Ivan T. Ivanov
2022-02-07 15:41       ` Ivan T. Ivanov

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