linux-kernel - Re: [PATCH v2] tps65910: Work around silicon erratum SWCZ010

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Message-ID: <53FC5DF0.2040205@nvidia.com>
Date:	Tue, 26 Aug 2014 15:44:08 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	"Arnout Vandecappelle (Essensium/Mind)" <arnout@...d.be>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	Mark Brown <broonie@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	David Brown <davidb@...eaurora.org>
Subject: Re: [PATCH v2] tps65910: Work around silicon erratum SWCZ010

Because this patch is dropped from Mark's tree, here is opportunity to 
revisit patch.

On Friday 22 August 2014 09:00 PM, Arnout Vandecappelle (Essensium/Mind) 
wrote:
>  From http://www.ti.com/lit/pdf/SWCZ010 :
>
>
> Workaround:
> Repeat I2C access.

> A simpler workaround is to make a dummy transfer just before the first
> access to the tps65910 chip. This can be done unconditionally.
> >id = chip_id;
>   
> +	/* Work around silicon erratum SWCZ010: the tps65910 may miss the
> +	 * first I2C transfer. So issue a dummy transfer before the first
> +	 * real transfer.
> +	 */
> +	i2c_master_send(i2c, "", 1);

I think dummy read is more safe operation than dummy write.
Dummy write can create the write on any register which can damage the 
critical settings or it may be possible that it will be incomplete 
calls. Datasheet has not been explained this clearly.


>   	

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