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From: Adrian Yanes <devel@ayanes.com>
To: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org, linux-i2c@vger.kernel.org
Subject: Re: [PATCH] i2c-at91: fix data-loss issue
Date: Wed, 25 Apr 2012 08:26:18 +0300	[thread overview]
Message-ID: <jn81tq$b3s$1@dough.gmane.org> (raw)
In-Reply-To: <4F94F598.1040008@ayanes.com>

Apparently the issue with the AT91RM9200 is the chipset itself due to a
factory design defect. Some people claim that the root cause of it is:

"Since the TWI doesn't have a DMA channel there is no way to deliver
timely data to the Tx buffer under heavy CPU load."[1]

Other threads[2] highlights same issues with the AT91RM9200 and the data
loss. Even in 2007, Ronny Nilsson tried to do some patch[3] blocking the
interrupts in order to win more feasibility, some testing was
performed[4], and up to 100kHz (exactly the same value as we started
getting errors), the driver just failed. At the end of the discussion
the conclusion was that the TWI controller of the AT91RM9200 is just
broken and the GPIO driver is the only alternative.

Therefore, your driver will work for all of those chipsets using PDC
with the TWI. However, it won't work with the AT91RM9200 (and probably
old hardware variants that keep same hardware design).

So I recommend to add a note/comment indicating such incompatibility for
the AT91RM9200, either in the source code or in the kernel config.

Thanks.

Adrian


1 - http://lists.atrpms.net/pipermail/i2c/2007-October/002026.html
2 - http://lists.lm-sensors.org/pipermail/i2c/2007-February/000773.html
3 - http://lists.lm-sensors.org/pipermail/i2c/2007-February/000833.html
4 - http://lists.atrpms.net/pipermail/i2c/2007-October/002034.html


  reply	other threads:[~2012-04-25  5:26 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-03-19 15:07 [PATCH v9 0/4] AT91: replace broken TWI driver i2c-at91.c Nikolaus Voss
2012-03-19 15:07 ` Nikolaus Voss
2011-11-08 10:49 ` [PATCH v9 1/4] drivers/i2c/busses/i2c-at91.c: remove broken driver Nikolaus Voss
2011-11-08 10:49   ` Nikolaus Voss
2011-11-08 10:49 ` [PATCH v9 3/4] drivers/i2c/busses/i2c-at91.c: add new driver Nikolaus Voss
2011-11-08 10:49   ` Nikolaus Voss
2012-04-13 10:17   ` Hubert Feurstein
2012-04-13 10:17     ` Hubert Feurstein
2012-04-13 10:17     ` Hubert Feurstein
2012-04-13 10:39     ` Felipe Balbi
2012-04-13 10:39       ` Felipe Balbi
2012-04-13 10:39       ` Felipe Balbi
2012-04-13 11:44       ` [PATCH] i2c-at91: fix data-loss issue Hubert Feurstein
2012-04-13 11:44         ` Hubert Feurstein
2012-04-13 11:44         ` Hubert Feurstein
2012-04-13 22:06         ` Ryan Mallon
2012-04-13 22:06           ` Ryan Mallon
2012-04-13 22:06           ` Ryan Mallon
2012-04-16  7:30         ` Voss, Nikolaus
2012-04-16  7:30           ` Voss, Nikolaus
2012-04-16  7:30           ` Voss, Nikolaus
2012-04-16  9:27           ` Hubert Feurstein
2012-04-16  9:27             ` Hubert Feurstein
2012-04-16  9:27             ` Hubert Feurstein
2012-04-18 14:39           ` Wolfram Sang
2012-04-18 14:39             ` Wolfram Sang
2012-04-18 14:39             ` Wolfram Sang
2012-04-21 19:33             ` Adrian Yanes
2012-04-23  5:39               ` Voss, Nikolaus
2012-04-23  5:39                 ` Voss, Nikolaus
2012-04-23  5:39                 ` Voss, Nikolaus
2012-04-23  6:24                 ` Adrian Yanes
2012-04-23  6:24                   ` Adrian Yanes
2012-04-23  6:24                   ` Adrian Yanes
2012-04-25  5:26                   ` Adrian Yanes [this message]
2011-11-08 11:09 ` [PATCH v9 2/4] Replace clk_lookup.con_id with clk_lookup.dev_id entries for twi clk Nikolaus Voss
2011-11-08 11:09   ` Nikolaus Voss
2011-11-08 11:11 ` [PATCH v9 4/4] G45 TWI: remove open drain setting for twi function gpios Nikolaus Voss
2011-11-08 11:11   ` Nikolaus Voss

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