From: Baruch Siach <baruch@tkos.co.il>
To: Wolfram Sang <wsa@the-dreams.de>
Cc: Andrew Jackson <Andrew.Jackson@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
"Du, Wenkai" <wenkai.du@intel.com>,
Shinya Kuribayashi <skuribay@pobox.com>,
Romain Baeriswyl <Romain.Baeriswyl@abilis.com>,
linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
Liviu Dudau <Liviu.Dudau@arm.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Mika Westerberg <mika.westerberg@linux.intel.com>
Subject: Re: [PATCH] i2c: designware: prevent early stop on TX FIFO empty
Date: Wed, 19 Nov 2014 15:35:32 +0200 [thread overview]
Message-ID: <20141119133531.GD2374@sapphire.tkos.co.il> (raw)
In-Reply-To: <20141119092122.GC1439@katana>
Hi Wolfram,
On Wed, Nov 19, 2014 at 10:21:22AM +0100, Wolfram Sang wrote:
> On Fri, Nov 07, 2014 at 12:10:44PM +0000, Andrew Jackson wrote:
> > If the Designware core is configured with IC_EMPTYFIFO_HOLD_MASTER_EN
> > set to zero, allowing the TX FIFO to become empty causes a STOP
> > condition to be generated on the I2C bus. If the transmit FIFO
> > threshold is set too high, an erroneous STOP condition can be
> > generated on long transfers - particularly where the interrupt
> > latency is extended.
> >
> > Signed-off-by: Andrew Jackson <Andrew.Jackson@arm.com>
> > Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
>
> So, what do other designware users think of this change (nice CC list
> BTW, Andrew). Adding Mika, too.
I don't have access to this hardware anymore so I can't test. As far as I
remember the spec this change should be OK.
baruch
> > drivers/i2c/busses/i2c-designware-core.c | 2 +-
> > 1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
> > index 3c20e4b..e070edd 100644
> > --- a/drivers/i2c/busses/i2c-designware-core.c
> > +++ b/drivers/i2c/busses/i2c-designware-core.c
> > @@ -363,7 +363,7 @@ int i2c_dw_init(struct dw_i2c_dev *dev)
> > }
> >
> > /* Configure Tx/Rx FIFO threshold levels */
> > - dw_writel(dev, dev->tx_fifo_depth - 1, DW_IC_TX_TL);
> > + dw_writel(dev, dev->tx_fifo_depth / 2, DW_IC_TX_TL);
> > dw_writel(dev, 0, DW_IC_RX_TL);
> >
> > /* configure the i2c master */
--
http://baruch.siach.name/blog/ ~. .~ Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
- baruch@tkos.co.il - tel: +972.2.679.5364, http://www.tkos.co.il -
next prev parent reply other threads:[~2014-11-19 13:44 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-07 12:10 [PATCH] i2c: designware: prevent early stop on TX FIFO empty Andrew Jackson
2014-11-19 9:21 ` Wolfram Sang
2014-11-19 13:35 ` Baruch Siach [this message]
2014-11-19 14:18 ` Mika Westerberg
2014-11-21 7:05 ` Wolfram Sang
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