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From: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
To: Andrey Danin <danindrey-JGs/UdohzUI@public.gmane.org>
Cc: Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>,
	devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	devel-tBiZLqfeLfOHmIFyCCdPziST3g8Odh+X@public.gmane.org,
	linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	ac100-oU9gvf+ajcQ97yFScArB1dHuzzzSOjJt@public.gmane.org,
	Laxman Dewangan
	<ldewangan-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
	Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>,
	Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>,
	Ian Campbell
	<ijc+devicetree-KcIKpvwj1kUDXYZnReoRVg@public.gmane.org>,
	Kumar Gala <galak-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>,
	Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>,
	Thierry Reding
	<thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Alexandre Courbot
	<gnurou-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Greg Kroah-Hartman
	<gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>,
	Julian Andres Klode <jak-4HMq4SXA452hPH1hqNUYSQ@public.gmane.org>,
	Marc Dietrich <marvin24-Mmb7MZpHnFY@public.gmane.org>
Subject: Re: [PATCH v3 1/4] i2c: tegra: implement slave mode
Date: Fri, 24 Jul 2015 12:52:51 +0200	[thread overview]
Message-ID: <20150724105251.GA22787@katana> (raw)
In-Reply-To: <55B210F4.6030700-JGs/UdohzUI@public.gmane.org>

[-- Attachment #1: Type: text/plain, Size: 973 bytes --]


> At the begin of my work on this patchset I even denied clock disable call if
> slave is registered (to minimize code that can affect transfer).

I hacked something like this, but it seems it was not enough.

> If only slave mode is used, then this logic is not needed.

This is not sufficent. We shouldn't break being a master only because we
also listen to a slave address (as long as the HW supports that of
course).

> tegra_i2c_init is called on probe and resume. Also it is called in case of
> xfer fail. If xfer is ok, then I think slave addr must be kept unchanged.

This is fragile. Try scanning the bus with i2cdetect and slave setup
will be gone.

> As far as I understand it is a loopback mode. Probably it will not work
> (Stephen Warren already mentioned this).

Just to make clear: I am not saying we should support talking to our own
slave address. But it should still be possible to communicate with other
remote devices on the bus.

Thanks,

   Wolfram

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WARNING: multiple messages have this Message-ID (diff)
From: wsa@the-dreams.de (Wolfram Sang)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v3 1/4] i2c: tegra: implement slave mode
Date: Fri, 24 Jul 2015 12:52:51 +0200	[thread overview]
Message-ID: <20150724105251.GA22787@katana> (raw)
In-Reply-To: <55B210F4.6030700@mail.ru>


> At the begin of my work on this patchset I even denied clock disable call if
> slave is registered (to minimize code that can affect transfer).

I hacked something like this, but it seems it was not enough.

> If only slave mode is used, then this logic is not needed.

This is not sufficent. We shouldn't break being a master only because we
also listen to a slave address (as long as the HW supports that of
course).

> tegra_i2c_init is called on probe and resume. Also it is called in case of
> xfer fail. If xfer is ok, then I think slave addr must be kept unchanged.

This is fragile. Try scanning the bus with i2cdetect and slave setup
will be gone.

> As far as I understand it is a loopback mode. Probably it will not work
> (Stephen Warren already mentioned this).

Just to make clear: I am not saying we should support talking to our own
slave address. But it should still be possible to communicate with other
remote devices on the bus.

Thanks,

   Wolfram
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WARNING: multiple messages have this Message-ID (diff)
From: Wolfram Sang <wsa@the-dreams.de>
To: Andrey Danin <danindrey@mail.ru>
Cc: Stephen Warren <swarren@wwwdotorg.org>,
	devicetree@vger.kernel.org, devel@linuxdriverproject.org,
	linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org,
	ac100@lists.launchpad.net, Laxman Dewangan <ldewangan@nvidia.com>,
	Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Ian Campbell <ijc+devicetree@hellion.org.uk>,
	Kumar Gala <galak@codeaurora.org>,
	Russell King <linux@arm.linux.org.uk>,
	Thierry Reding <thierry.reding@gmail.com>,
	Alexandre Courbot <gnurou@gmail.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Julian Andres Klode <jak@jak-linux.org>,
	Marc Dietrich <marvin24@gmx.de>
Subject: Re: [PATCH v3 1/4] i2c: tegra: implement slave mode
Date: Fri, 24 Jul 2015 12:52:51 +0200	[thread overview]
Message-ID: <20150724105251.GA22787@katana> (raw)
In-Reply-To: <55B210F4.6030700@mail.ru>

[-- Attachment #1: Type: text/plain, Size: 973 bytes --]


> At the begin of my work on this patchset I even denied clock disable call if
> slave is registered (to minimize code that can affect transfer).

I hacked something like this, but it seems it was not enough.

> If only slave mode is used, then this logic is not needed.

This is not sufficent. We shouldn't break being a master only because we
also listen to a slave address (as long as the HW supports that of
course).

> tegra_i2c_init is called on probe and resume. Also it is called in case of
> xfer fail. If xfer is ok, then I think slave addr must be kept unchanged.

This is fragile. Try scanning the bus with i2cdetect and slave setup
will be gone.

> As far as I understand it is a loopback mode. Probably it will not work
> (Stephen Warren already mentioned this).

Just to make clear: I am not saying we should support talking to our own
slave address. But it should still be possible to communicate with other
remote devices on the bus.

Thanks,

   Wolfram

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  parent reply	other threads:[~2015-07-24 10:52 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-07-20 20:35 [PATCH v3 0/4] arm: tegra: implement NVEC driver using tegra i2c Andrey Danin
2015-07-20 20:35 ` Andrey Danin
2015-07-20 20:35 ` Andrey Danin
     [not found] ` <1437424546-30405-1-git-send-email-danindrey-JGs/UdohzUI@public.gmane.org>
2015-07-20 20:35   ` [PATCH v3 1/4] i2c: tegra: implement slave mode Andrey Danin
2015-07-20 20:35     ` Andrey Danin
2015-07-20 20:35     ` Andrey Danin
2015-07-24  9:27     ` Wolfram Sang
2015-07-24  9:27       ` Wolfram Sang
2015-07-24 10:18       ` Andrey Danin
2015-07-24 10:18         ` Andrey Danin
     [not found]         ` <55B210F4.6030700-JGs/UdohzUI@public.gmane.org>
2015-07-24 10:52           ` Wolfram Sang [this message]
2015-07-24 10:52             ` Wolfram Sang
2015-07-24 10:52             ` Wolfram Sang
2015-08-20 12:14             ` Andrey Danin
2015-08-20 12:14               ` Andrey Danin
2015-08-20 12:14               ` Andrey Danin
2015-08-20 12:14               ` Andrey Danin
     [not found]               ` <55D5C4AA.2000307-JGs/UdohzUI@public.gmane.org>
2015-09-08 11:46                 ` Wolfram Sang
2015-09-08 11:46                   ` Wolfram Sang
2015-09-08 11:46                   ` Wolfram Sang
2015-09-08 12:31                   ` Andrey Danin
2015-09-08 12:31                     ` Andrey Danin
2015-09-08 12:31                     ` Andrey Danin
2015-07-20 20:35   ` [PATCH v3 2/4] staging/nvec: reimplement on top of tegra i2c driver Andrey Danin
2015-07-20 20:35     ` Andrey Danin
2015-07-20 20:35     ` Andrey Danin
     [not found]     ` <1437424546-30405-3-git-send-email-danindrey-JGs/UdohzUI@public.gmane.org>
2015-07-20 22:18       ` Stephen Warren
2015-07-20 22:18         ` Stephen Warren
2015-07-20 22:18         ` Stephen Warren
2015-07-20 20:35   ` [PATCH v3 3/4] staging/nvec: remove old code Andrey Danin
2015-07-20 20:35     ` Andrey Danin
2015-07-20 20:35     ` Andrey Danin
2015-07-20 20:35   ` [PATCH v3 4/4] dt: paz00: define nvec as child of i2c bus Andrey Danin
2015-07-20 20:35     ` Andrey Danin
2015-07-20 20:35     ` Andrey Danin
2015-07-20 22:19     ` Stephen Warren
2015-07-20 22:19       ` Stephen Warren
     [not found]       ` <55AD73F4.2050502-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
2015-07-21  6:35         ` Andrey Danin
2015-07-21  6:35           ` Andrey Danin
2015-07-21  6:35           ` Andrey Danin
2015-07-21  8:25           ` Marc Dietrich
2015-07-21  8:25             ` Marc Dietrich
2015-07-21  8:25             ` Marc Dietrich
2015-07-21  8:51             ` Andrey Danin
2015-07-21  8:51               ` Andrey Danin
2015-07-21  8:51               ` Andrey Danin
     [not found]               ` <55AE0803.10603-JGs/UdohzUI@public.gmane.org>
2015-07-21 11:57                 ` Marc Dietrich
2015-07-21 11:57                   ` Marc Dietrich
2015-07-21 11:57                   ` Marc Dietrich
2015-07-21 20:52                   ` Wolfram Sang
2015-07-21 20:52                     ` Wolfram Sang
2015-07-21 20:52                     ` Wolfram Sang
2015-07-21  8:38   ` [PATCH v3 0/4] arm: tegra: implement NVEC driver using tegra i2c Andrey Danin
2015-07-21  8:38     ` Andrey Danin
2015-07-21  8:38     ` Andrey Danin

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