> >>>> That's odd because it suggests that DMA actually completed, but the > >>>> message didn't. > >>>> > >>>> I'm not sure I understand how that could happen. > >>>> > >>>> What's also weird above is that there doesn't seem to be a DMA that > >>>> is started for that particular message. Or is the timeout message a > >>>> response to the prior transfer (length 10)? Seems like that should > >>>> not be possible because we get the "transfer complete" message. > >>> > >>> Wait, those are actually different instances of the I2C controller, > >>> so the relevant log entries are these: > >>> > >>> [ 0.945445] tegra-i2c 7000d000.i2c: starting DMA for length: 16 > >>> [ 0.945456] tegra-i2c 7000d000.i2c: unmasked irq: 0c > >>> ... > >>> [ 1.049224] tegra-i2c 7000d000.i2c: i2c transfer timed out > >>> > >>> And these don't happen if you use higher burst sizes or before the > >>> DMA series? > >> > >> I tried to enforce DMA without changing bursts: > >> > >> ---------- > >> diff --git a/drivers/i2c/busses/i2c-tegra.c > >> b/drivers/i2c/busses/i2c-tegra.c index c538ed5f8e2c..5d1c54ce7800 > >> 100644 > >> --- a/drivers/i2c/busses/i2c-tegra.c > >> +++ b/drivers/i2c/busses/i2c-tegra.c > >> @@ -6,6 +6,8 @@ > >> * Author: Colin Cross <ccross@xxxxxxxxxxx> > >> */ > >> > >> +#define DEBUG > >> + > >> #include <linux/clk.h> > >> #include <linux/delay.h> > >> #include <linux/dmaengine.h> > >> @@ -1046,8 +1048,7 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev, > >> xfer_size = msg->len + I2C_PACKET_HEADER_SIZE; > >> > >> xfer_size = ALIGN(xfer_size, BYTES_PER_FIFO_WORD); > >> - i2c_dev->is_curr_dma_xfer = (xfer_size > I2C_PIO_MODE_MAX_LEN) && > >> - i2c_dev->dma_buf; > >> + i2c_dev->is_curr_dma_xfer = !!i2c_dev->dma_buf; > >> tegra_i2c_config_fifo_trig(i2c_dev, xfer_size); > >> dma = i2c_dev->is_curr_dma_xfer; > >> ---------- > >> > >> Here is the log with this change: > >> > >> [ 0.760796] tegra_rtc 7000e000.rtc: registered as rtc1 > >> [ 0.760850] tegra_rtc 7000e000.rtc: Tegra internal Real Time Clock > >> [ 0.761050] i2c /dev entries driver > >> [ 0.918928] tegra-i2c 7000c000.i2c: starting DMA for length: 16 > >> [ 0.918940] tegra-i2c 7000c000.i2c: unmasked irq: 0c > >> [ 0.919040] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0 > >> [ 0.919050] tegra-i2c 7000c000.i2c: starting DMA for length: 8 > >> [ 0.919059] tegra-i2c 7000c000.i2c: unmasked irq: 0c > >> [ 0.919322] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0 > >> [ 0.919335] tegra-i2c 7000c000.i2c: starting DMA for length: 16 > >> [ 0.919343] tegra-i2c 7000c000.i2c: unmasked irq: 0c > >> [ 0.919440] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0 > >> [ 0.919448] tegra-i2c 7000c000.i2c: starting DMA for length: 112 > >> [ 0.919456] tegra-i2c 7000c000.i2c: unmasked irq: 0c > >> [ 0.922818] tegra-i2c 7000c000.i2c: transfer complete: 11 0 0 > >> [ 0.922829] atmel_mxt_ts 0-004c: Family: 160 Variant: 0 Firmware V1.0.AA Objects: 18 > >> [ 0.922886] tegra-i2c 7000c000.i2c: starting DMA for length: 16 > >> [ 0.922895] tegra-i2c 7000c000.i2c: unmasked irq: 0c > >> [ 0.922993] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0 > >> [ 0.923002] tegra-i2c 7000c000.i2c: starting DMA for length: 224 > >> [ 0.923011] tegra-i2c 7000c000.i2c: unmasked irq: 0c > >> [ 0.933253] tegra-i2c 7000c000.i2c: transfer complete: 11 0 0 > >> [ 0.933287] tegra-i2c 7000c000.i2c: starting DMA for length: 16 > >> [ 0.933297] tegra-i2c 7000c000.i2c: unmasked irq: 0c > >> [ 0.933478] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0 > >> [ 0.933487] tegra-i2c 7000c000.i2c: starting DMA for length: 12 > >> [ 0.933496] tegra-i2c 7000c000.i2c: unmasked irq: 0c > >> [ 0.945120] tegra-i2c 7000d000.i2c: starting DMA for length: 16 > >> [ 0.945130] tegra-i2c 7000d000.i2c: unmasked irq: 0c > >> [ 1.038917] tegra-i2c 7000c000.i2c: DMA transfer timeout > >> [ 1.038982] atmel_mxt_ts 0-004c: __mxt_read_reg: i2c transfer failed (-110) > >> [ 1.039000] tegra-i2c 7000c000.i2c: starting DMA for length: 16 > >> [ 1.039006] atmel_mxt_ts 0-004c: Failed to read T44 and T5 (-110) > >> [ 1.039009] tegra-i2c 7000c000.i2c: unmasked irq: 0c > >> [ 1.039148] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0 > >> [ 1.039157] tegra-i2c 7000c000.i2c: starting DMA for length: 4 > >> [ 1.039166] tegra-i2c 7000c000.i2c: unmasked irq: 0c > >> [ 1.039304] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0 > >> [ 1.039340] tegra-i2c 7000c000.i2c: starting DMA for length: 16 > >> [ 1.039349] tegra-i2c 7000c000.i2c: unmasked irq: 0c > >> [ 1.039535] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0 > >> [ 1.039544] tegra-i2c 7000c000.i2c: starting DMA for length: 12 > >> [ 1.039552] tegra-i2c 7000c000.i2c: unmasked irq: 0c > >> [ 1.040055] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0 > >> [ 1.040083] tegra-i2c 7000c000.i2c: starting DMA for length: 16 > >> [ 1.040092] tegra-i2c 7000c000.i2c: unmasked irq: 0c > >> [ 1.040301] tegra-i2c 7000c000.i2c: transfer complete: 10 0 0 > >> [ 1.048934] tegra-i2c 7000d000.i2c: i2c transfer timed out > > > > This log shows DMA transfer timeout for atmel read. > > Do you see issue if you don’t enforce dma all time and let it choose PIO Vs DMA? > > > > No, there are no timeout errors in PIO mode. I could post full log with the PIO-only mode if you want. > Yes please post full log of PIO only and DMA only
