* [PATCH] i2c: designware: prevent early stop on TX FIFO empty @ 2014-11-07 12:10 Andrew Jackson 2014-11-19 9:21 ` Wolfram Sang 2014-11-21 7:05 ` Wolfram Sang 0 siblings, 2 replies; 5+ messages in thread From: Andrew Jackson @ 2014-11-07 12:10 UTC (permalink / raw) To: Wolfram Sang, Andrew Morton, Baruch Siach, Du, Wenkai, Shinya Kuribayashi, Romain Baeriswyl, linux-i2c, linux-kernel Cc: Liviu Dudau, linux-arm-kernel 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> --- 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 */ -- 1.7.1 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] i2c: designware: prevent early stop on TX FIFO empty 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 2014-11-19 14:18 ` Mika Westerberg 2014-11-21 7:05 ` Wolfram Sang 1 sibling, 2 replies; 5+ messages in thread From: Wolfram Sang @ 2014-11-19 9:21 UTC (permalink / raw) To: Andrew Jackson Cc: Andrew Morton, Baruch Siach, Du, Wenkai, Shinya Kuribayashi, Romain Baeriswyl, linux-i2c, linux-kernel, Liviu Dudau, linux-arm-kernel, Mika Westerberg [-- Attachment #1: Type: text/plain, Size: 1338 bytes --] 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. > --- > 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 */ > -- > 1.7.1 > [-- Attachment #2: Digital signature --] [-- Type: application/pgp-signature, Size: 819 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] i2c: designware: prevent early stop on TX FIFO empty 2014-11-19 9:21 ` Wolfram Sang @ 2014-11-19 13:35 ` Baruch Siach 2014-11-19 14:18 ` Mika Westerberg 1 sibling, 0 replies; 5+ messages in thread From: Baruch Siach @ 2014-11-19 13:35 UTC (permalink / raw) To: Wolfram Sang Cc: Andrew Jackson, Andrew Morton, Du, Wenkai, Shinya Kuribayashi, Romain Baeriswyl, linux-i2c, linux-kernel, Liviu Dudau, linux-arm-kernel, Mika Westerberg 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 - ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] i2c: designware: prevent early stop on TX FIFO empty 2014-11-19 9:21 ` Wolfram Sang 2014-11-19 13:35 ` Baruch Siach @ 2014-11-19 14:18 ` Mika Westerberg 1 sibling, 0 replies; 5+ messages in thread From: Mika Westerberg @ 2014-11-19 14:18 UTC (permalink / raw) To: Wolfram Sang Cc: Andrew Jackson, Andrew Morton, Baruch Siach, Du, Wenkai, Shinya Kuribayashi, Romain Baeriswyl, linux-i2c, linux-kernel, Liviu Dudau, linux-arm-kernel 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. Makes sense to give some slack so that the interrupt handler is still able to fill the FIFO. > > > > 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 quickly tested this on Haswell machine with touch screen connected to the I2C bus and it still works fine, so Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com> ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] i2c: designware: prevent early stop on TX FIFO empty 2014-11-07 12:10 [PATCH] i2c: designware: prevent early stop on TX FIFO empty Andrew Jackson 2014-11-19 9:21 ` Wolfram Sang @ 2014-11-21 7:05 ` Wolfram Sang 1 sibling, 0 replies; 5+ messages in thread From: Wolfram Sang @ 2014-11-21 7:05 UTC (permalink / raw) To: Andrew Jackson Cc: Andrew Morton, Baruch Siach, Du, Wenkai, Shinya Kuribayashi, Romain Baeriswyl, linux-i2c, linux-kernel, Liviu Dudau, linux-arm-kernel [-- Attachment #1: Type: text/plain, Size: 577 bytes --] 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> Applied to for-current, thanks! [-- Attachment #2: Digital signature --] [-- Type: application/pgp-signature, Size: 819 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2014-11-21 7:04 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 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 2014-11-19 14:18 ` Mika Westerberg 2014-11-21 7:05 ` Wolfram Sang
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