From mboxrd@z Thu Jan 1 00:00:00 1970 From: dgilbert@interlog.com (Douglas Gilbert) Date: Sat, 24 Jan 2015 23:42:24 +0100 Subject: [PATCH] at91: i2c-at91: improve time-out handling In-Reply-To: <20150113152752.GK7660@katana> References: <54A58BA5.3080003@interlog.com> <20150107103113.GA30897@ldesroches-Latitude-E6320> <20150113152752.GK7660@katana> Message-ID: <54C41FD0.2010607@interlog.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 >> Regards >> >> Ludovic >> >>> Signed-off-by: Douglas Gilbert >> >>> 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: