Re: [PATCH V12 3/5] i2c: tegra: Add DMA support
From: Dmitry Osipenko
Date: Wed Feb 06 2019 - 08:18:30 EST
06.02.2019 16:13, Thierry Reding ÐÐÑÐÑ:
[snip]
>> 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