RE: [PATCH V12 3/5] i2c: tegra: Add DMA support

[Sowjanya Komatineni]

> > > >>>> 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 donât 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 Also, in above log, 
> > lots of DMA transfer went thru fine except this one transfer where DMA 
> > timed out.
> > DMA completion doesnt happen on DMA submit during this particular 
> > transaction timeframe for some reason.
> 
> Dmitry, can you provide some background information on the setup that you're using? I vaguely remember something about i2c@7000d000 being special on > older Tegra devices. Perhaps there's something additional that we need to take into account?
> 
> Aha! Look at tegra_i2c_reg_addr() which special-cases I2C_TX_FIFO on the DVC variant of the controller, which is exactly the one that you are seeing > the timeouts on and it's exactly the register that we use as destination for the DMA transfer.
> 
> I think we need to do something like this:
> 
> 	slv_config.dst_addr = i2c_dev->base_phys + tegra_i2c_reg_addr(i2c_dev, I2C_TX_FIFO);
> 
> to make sure we pass the right FIFO register address to DMA.
> 
> Thierry
> 
Yeah DVC FIFO register offset is different. Yes we need to use tegra_i2c_reg_addr which takes care of DVC FIFO address. Will fix it.

Atmel touch is on I2C1 (7000C000). DMA Timeout happened for only 1 transaction for this device and lots of other transfers to this device are fine.
in other log dmitry sent, we see one transfer timeout from 7000D000 and this could be due to FIFO Addresses.

Sowjanya