* [PATCH] at91: i2c-at91: improve time-out handling
@ 2015-01-01 18:02 Douglas Gilbert
2015-01-07 10:31 ` Ludovic Desroches
0 siblings, 1 reply; 6+ messages in thread
From: Douglas Gilbert @ 2015-01-01 18:02 UTC (permalink / raw)
To: linux-arm-kernel
With lk 3.19.0-rc2 and a at91sam9g25 (9x5) based system I
connected a NXP SC16IS750 I2C to serial bridge. After
routing the 750's IRQ back to the sc16is7xx driver and some
simple successful test, it was time for some intense testing:
Tx looped back to Rx on the 750, open picocom on /dev/ttySC0
at 38400, and use hexdump to blast a binary file (in hex) at
ttySC0. The I2C SCL speed was 200,000 Hz.
It worked as expected for a few seconds then it wedged the
I2C bus. That was repeatable. In the cases that I checked SCL
was high, SDA was low (driven by _both_ the G25's macrocell
and the 750!!) and IRQ was active (low). This patch stopped
the G25 macrocell from driving SDA low in the above wedge
(and stopped copious error reports going to the log). I was
surprised that a NXP I2C chip got into this situation, IMO
SDA on a slave should have a driven low timeout. IMO all
I2C master drivers should have provision to drive a gpio
connected to a (or all the) slave's RESET line(s).
ChangeLog:
when handling an I2C bus time-out, first clean-up the
DMA transfer, then do an I2C macrocell software reset
and restore some registers, including the interrupt
mask
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: i2c-at91-timeout1.patch
Type: text/x-patch
Size: 972 bytes
Desc: not available
URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20150101/fd42e097/attachment.bin>
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH] at91: i2c-at91: improve time-out handling 2015-01-01 18:02 [PATCH] at91: i2c-at91: improve time-out handling Douglas Gilbert @ 2015-01-07 10:31 ` Ludovic Desroches 2015-01-13 15:27 ` Wolfram Sang 0 siblings, 1 reply; 6+ messages in thread From: Ludovic Desroches @ 2015-01-07 10:31 UTC (permalink / raw) To: linux-arm-kernel Hi Douglas, On Thu, Jan 01, 2015 at 01:02:13PM -0500, Douglas Gilbert wrote: > With lk 3.19.0-rc2 and a at91sam9g25 (9x5) based system I > connected a NXP SC16IS750 I2C to serial bridge. After > routing the 750's IRQ back to the sc16is7xx driver and some > simple successful test, it was time for some intense testing: > Tx looped back to Rx on the 750, open picocom on /dev/ttySC0 > at 38400, and use hexdump to blast a binary file (in hex) at > ttySC0. The I2C SCL speed was 200,000 Hz. > > It worked as expected for a few seconds then it wedged the > I2C bus. That was repeatable. In the cases that I checked SCL > was high, SDA was low (driven by _both_ the G25's macrocell > and the 750!!) and IRQ was active (low). This patch stopped > the G25 macrocell from driving SDA low in the above wedge > (and stopped copious error reports going to the log). I was > surprised that a NXP I2C chip got into this situation, IMO > SDA on a slave should have a driven low timeout. IMO all > I2C master drivers should have provision to drive a gpio > connected to a (or all the) slave's RESET line(s). > > > ChangeLog: > when handling an I2C bus time-out, first clean-up the > DMA transfer, then do an I2C macrocell software reset > and restore some registers, including the interrupt > mask > I am wondering why you need to call at91_twi_irq_save() and at91_twi_irq_restore(). The interrupts enabled in the driver are AT91_TWI_TXCOMP, AT91_TWI_RXRDY and AT91_TWI_TXRDY and they are managed in at91_do_twi_transfer() so they would be set correctly for the next transfer. Regards Ludovic > Signed-off-by: Douglas Gilbert <dgilbert@interlog.com> > diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c > index 636fd2e..4d78708 100644 > --- a/drivers/i2c/busses/i2c-at91.c > +++ b/drivers/i2c/busses/i2c-at91.c > @@ -382,6 +382,7 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) > { > int ret; > bool has_unre_flag = dev->pdata->has_unre_flag; > + bool timed_out = false; > > dev_dbg(dev->dev, "transfer: %s %d bytes.\n", > (dev->msg->flags & I2C_M_RD) ? "read" : "write", dev->buf_len); > @@ -440,7 +441,7 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) > dev->adapter.timeout); > if (ret == 0) { > dev_err(dev->dev, "controller timed out\n"); > - at91_init_twi_bus(dev); > + timed_out = true; > ret = -ETIMEDOUT; > goto error; > } > @@ -471,6 +472,11 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) > > error: > at91_twi_dma_cleanup(dev); > + if (timed_out) { > + at91_twi_irq_save(dev); > + at91_init_twi_bus(dev); > + at91_twi_irq_restore(dev); > + } > return ret; > } > ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] at91: i2c-at91: improve time-out handling 2015-01-07 10:31 ` Ludovic Desroches @ 2015-01-13 15:27 ` Wolfram Sang 2015-01-24 22:42 ` Douglas Gilbert 0 siblings, 1 reply; 6+ messages in thread From: Wolfram Sang @ 2015-01-13 15:27 UTC (permalink / raw) To: linux-arm-kernel On Wed, Jan 07, 2015 at 11:31:14AM +0100, Ludovic Desroches wrote: > Hi Douglas, > > On Thu, Jan 01, 2015 at 01:02:13PM -0500, Douglas Gilbert wrote: > > With lk 3.19.0-rc2 and a at91sam9g25 (9x5) based system I > > connected a NXP SC16IS750 I2C to serial bridge. After > > routing the 750's IRQ back to the sc16is7xx driver and some > > simple successful test, it was time for some intense testing: > > Tx looped back to Rx on the 750, open picocom on /dev/ttySC0 > > at 38400, and use hexdump to blast a binary file (in hex) at > > ttySC0. The I2C SCL speed was 200,000 Hz. > > > > It worked as expected for a few seconds then it wedged the > > I2C bus. That was repeatable. In the cases that I checked SCL > > was high, SDA was low (driven by _both_ the G25's macrocell > > and the 750!!) and IRQ was active (low). This patch stopped > > the G25 macrocell from driving SDA low in the above wedge > > (and stopped copious error reports going to the log). I was > > surprised that a NXP I2C chip got into this situation, IMO > > SDA on a slave should have a driven low timeout. IMO all > > I2C master drivers should have provision to drive a gpio > > connected to a (or all the) slave's RESET line(s). > > > > > > ChangeLog: > > when handling an I2C bus time-out, first clean-up the > > DMA transfer, then do an I2C macrocell software reset > > and restore some registers, including the interrupt > > mask > > > > I am wondering why you need to call at91_twi_irq_save() and > at91_twi_irq_restore(). The interrupts enabled in the driver are > AT91_TWI_TXCOMP, AT91_TWI_RXRDY and AT91_TWI_TXRDY and they are managed > in at91_do_twi_transfer() so they would be set correctly for the next > transfer. Douglas, any more info you could provide? > > Regards > > Ludovic > > > Signed-off-by: Douglas Gilbert <dgilbert@interlog.com> > > > diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c > > index 636fd2e..4d78708 100644 > > --- a/drivers/i2c/busses/i2c-at91.c > > +++ b/drivers/i2c/busses/i2c-at91.c > > @@ -382,6 +382,7 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) > > { > > int ret; > > bool has_unre_flag = dev->pdata->has_unre_flag; > > + bool timed_out = false; > > > > dev_dbg(dev->dev, "transfer: %s %d bytes.\n", > > (dev->msg->flags & I2C_M_RD) ? "read" : "write", dev->buf_len); > > @@ -440,7 +441,7 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) > > dev->adapter.timeout); > > if (ret == 0) { > > dev_err(dev->dev, "controller timed out\n"); > > - at91_init_twi_bus(dev); > > + timed_out = true; > > ret = -ETIMEDOUT; > > goto error; > > } > > @@ -471,6 +472,11 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) > > > > error: > > at91_twi_dma_cleanup(dev); > > + if (timed_out) { > > + at91_twi_irq_save(dev); > > + at91_init_twi_bus(dev); > > + at91_twi_irq_restore(dev); > > + } > > return ret; > > } > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-i2c" in > the body of a message to majordomo at vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: Digital signature URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20150113/11164d33/attachment-0001.sig> ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] at91: i2c-at91: improve time-out handling 2015-01-13 15:27 ` Wolfram Sang @ 2015-01-24 22:42 ` Douglas Gilbert 2015-01-26 17:19 ` Mark Roszko 0 siblings, 1 reply; 6+ messages in thread From: Douglas Gilbert @ 2015-01-24 22:42 UTC (permalink / raw) To: linux-arm-kernel On 15-01-13 04:27 PM, Wolfram Sang wrote: > On Wed, Jan 07, 2015 at 11:31:14AM +0100, Ludovic Desroches wrote: >> Hi Douglas, >> >> On Thu, Jan 01, 2015 at 01:02:13PM -0500, Douglas Gilbert wrote: >>> With lk 3.19.0-rc2 and a at91sam9g25 (9x5) based system I >>> connected a NXP SC16IS750 I2C to serial bridge. After >>> routing the 750's IRQ back to the sc16is7xx driver and some >>> simple successful test, it was time for some intense testing: >>> Tx looped back to Rx on the 750, open picocom on /dev/ttySC0 >>> at 38400, and use hexdump to blast a binary file (in hex) at >>> ttySC0. The I2C SCL speed was 200,000 Hz. >>> >>> It worked as expected for a few seconds then it wedged the >>> I2C bus. That was repeatable. In the cases that I checked SCL >>> was high, SDA was low (driven by _both_ the G25's macrocell >>> and the 750!!) and IRQ was active (low). This patch stopped >>> the G25 macrocell from driving SDA low in the above wedge >>> (and stopped copious error reports going to the log). I was >>> surprised that a NXP I2C chip got into this situation, IMO >>> SDA on a slave should have a driven low timeout. IMO all >>> I2C master drivers should have provision to drive a gpio >>> connected to a (or all the) slave's RESET line(s). >>> >>> >>> ChangeLog: >>> when handling an I2C bus time-out, first clean-up the >>> DMA transfer, then do an I2C macrocell software reset >>> and restore some registers, including the interrupt >>> mask >>> >> >> I am wondering why you need to call at91_twi_irq_save() and >> at91_twi_irq_restore(). The interrupts enabled in the driver are >> AT91_TWI_TXCOMP, AT91_TWI_RXRDY and AT91_TWI_TXRDY and they are managed >> in at91_do_twi_transfer() so they would be set correctly for the next >> transfer. > > Douglas, any more info you could provide? I reran the torture tests without the at91_twi_irq_save() and at91_twi_irq_restore() calls and got the same results. So it seems that those calls are not needed; revised patch attached. Other observations: after the torture test wedges (after several seconds at 38400 baud) grounding the RESET pin on the SC16IS750 clears the I2C bus jam; thereafter I2C transmissions can continue. That implies to me that Atmel's I2C macrocell is not wedged. When the sc16is7xx driver is built as a module, then rmmod runs into a slow path dump in the logs. That comes from the clk_disable() call in: sc16is7xx_i2c_remove+0x88/0xa4 [sc16is7xx] Tests done with lk 3.19.0-rc4 using a AT91SAM9G25 system (Acme Arietta). For the attached patch: Signed-off-by: Douglas Gilbert <dgilbert@interlog.com> >> Regards >> >> Ludovic >> >>> Signed-off-by: Douglas Gilbert <dgilbert@interlog.com> >> >>> diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c >>> index 636fd2e..4d78708 100644 >>> --- a/drivers/i2c/busses/i2c-at91.c >>> +++ b/drivers/i2c/busses/i2c-at91.c >>> @@ -382,6 +382,7 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) >>> { >>> int ret; >>> bool has_unre_flag = dev->pdata->has_unre_flag; >>> + bool timed_out = false; >>> >>> dev_dbg(dev->dev, "transfer: %s %d bytes.\n", >>> (dev->msg->flags & I2C_M_RD) ? "read" : "write", dev->buf_len); >>> @@ -440,7 +441,7 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) >>> dev->adapter.timeout); >>> if (ret == 0) { >>> dev_err(dev->dev, "controller timed out\n"); >>> - at91_init_twi_bus(dev); >>> + timed_out = true; >>> ret = -ETIMEDOUT; >>> goto error; >>> } >>> @@ -471,6 +472,11 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) >>> >>> error: >>> at91_twi_dma_cleanup(dev); >>> + if (timed_out) { >>> + at91_twi_irq_save(dev); >>> + at91_init_twi_bus(dev); >>> + at91_twi_irq_restore(dev); >>> + } >>> return ret; >>> } >>> >> -------------- next part -------------- A non-text attachment was scrubbed... Name: i2c-at91_tmout2.patch Type: text/x-patch Size: 1570 bytes Desc: not available URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20150124/c0035c2f/attachment.bin> ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] at91: i2c-at91: improve time-out handling 2015-01-24 22:42 ` Douglas Gilbert @ 2015-01-26 17:19 ` Mark Roszko 2015-02-05 19:40 ` Wolfram Sang 0 siblings, 1 reply; 6+ messages in thread From: Mark Roszko @ 2015-01-26 17:19 UTC (permalink / raw) To: linux-arm-kernel You can check if ret == -ETIMEDOUT in the error path instead of allocating another variable. You also generated the patch with your /arch/arm/boot/dts/Makefile changes. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] at91: i2c-at91: improve time-out handling 2015-01-26 17:19 ` Mark Roszko @ 2015-02-05 19:40 ` Wolfram Sang 0 siblings, 0 replies; 6+ messages in thread From: Wolfram Sang @ 2015-02-05 19:40 UTC (permalink / raw) To: linux-arm-kernel On Mon, Jan 26, 2015 at 12:19:23PM -0500, Mark Roszko wrote: > You can check if ret == -ETIMEDOUT in the error path instead of > allocating another variable. > > You also generated the patch with your /arch/arm/boot/dts/Makefile changes. True. Someone cares to respin this patch? -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: Digital signature URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20150205/8e88ba10/attachment.sig> ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2015-02-05 19:40 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2015-01-01 18:02 [PATCH] at91: i2c-at91: improve time-out handling Douglas Gilbert 2015-01-07 10:31 ` Ludovic Desroches 2015-01-13 15:27 ` Wolfram Sang 2015-01-24 22:42 ` Douglas Gilbert 2015-01-26 17:19 ` Mark Roszko 2015-02-05 19:40 ` Wolfram Sang
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).