On Tue, 2016-05-24 at 20:37 +0300, Andy Shevchenko wrote:

On Thu, 2016-05-19 at 02:18 +0100, Bryan O'Donoghue wrote:

quoted

On Thu, 2016-05-12 at 18:06 +0300, Andy Shevchenko wrote:

quoted

On Fri, 2016-05-06 at 18:17 +0300, Andy Shevchenko wrote:

quoted

This is combined series of two things:
- split out the Intel LPSS specific driver from 8250_pci into
8250_lpss
- enable DMA support on Intel Quark UART

The patch has been tested on few Intel SoCs / platforms. In any
case I
would
like to ask Bryan to do independent test.

Andy.

It looks as though there's a performance drop when enabling the DMA
here (v) stock PIO mode with the 8250 driver.

Wait, the time measurement you done is unrelated to DMA/non-DMA mode.
It's significantly depend to the speed of the port.

It would be better to have 1000(s) of iterations to see any steady
difference out of statistical error. Below result doesn't show anything
like this.

I also tried on my Galileo board, I used longer data stream, i.e. output
of dmesg (since your data pattern makes 0:s in statistics) and got
something quite near to each other:

###
Size of the data (it actually become few dozens of bytes (55 bytes to be
precise) bigger since one message had been printed in the second part of
high speed test
###

% dmesg | wc -c
34965

### Low speed, DMA mode enabled by default ###
% stty -F /dev/ttyS0 9600

% time dmesg > /dev/ttyS0
real    0m 34.22s
user    0m 0.01s
sys     0m 0.02s

NOTE: Transfer speed: 34965b/34.22s ~= 1021.77b/s (9600 baud)

### non-DMA mode ###
% echo 3 > /sys/class/tty/ttyS0/dma_mode 

% time dmesg > /dev/ttyS0
real    0m 36.09s
user    0m 0.01s
sys     0m 0.02s

### Higher speed ###

% stty -F /dev/ttyS0 921600

% time dmesg > /dev/ttyS0
real    0m 0.41s
user    0m 0.01s
sys     0m 0.03s

NOTE: Transfer speed: 34965b/0.41s ~= 85280.49b/s (921600 baud)

### DMA mode enabled ###
% echo 0 > /sys/class/tty/ttyS0/dma_mode 

% time dmesg > /dev/ttyS0
real    0m 0.41s
user    0m 0.01s
sys     0m 0.02s

Below results doesn't show DMA case (by the way, how did you disable
DMA
in 3.8.7?) for stock kernel.

Anyway, I added preliminary support to change DMA mode run-time. Check
my today topic/dw/qrk branch. It would be nice to see all 4 cases: DMA
vs non-DMA on stock kernel (Yocto) and mine.

P.S. What is the point to test arbitrary tip branch?

quoted

Test setup Galileo Gen1 transmitter - Galileo Gen2 receiver. TX/RX
cross-wired between the Arduino UART headers respectively (pins 0 &
1
on the "Digital PWM" header), GND pin14 similarly cross-wired.

User-space:
    Receiver: Stock on-flash yocto-tiny kernel 3.8.7
    Transmitter: Galileo Debian image :
                 https://sourceforge.net/projects/galileodebian/
    3.8.7 kernel: On SPI-flash BSP kernel
    andy-v4: From your tree
             d13ffcf ('serial: 8250: attempt to keep Kconfig and
                       Makefile in order')
    tip-of-tree : 97f0090 ('Merge tag 'rproc-v4.7' of
                            git://github.com/andersson/remoteproc')

Results:

### Test0 ###

galileo dma andy-v4 9600 8n1 

root@galileo:~# time echo "abcdefghijklmnopqrstuvwxyz0123456789" >
/dev/ttyS0

real    0m0.060s
user    0m0.000s
sys     0m0.000s


galileo non-dma Linux 3.8.7 9600 8n1:

9600 8n1
root@galileo:~# time echo "abcdefghijklmnopqrstuvwxyz0123456789" >
/dev/ttyS0

real    0m0.051s
user    0m0.000s
sys     0m0.000s

galileo non-dma tip-of-tree 9600 8n1:

root@galileo:~# time echo "abcdefghijklmnopqrstuvwxyz0123456789" >
/dev/ttyS0

real    0m0.048s
user    0m0.000s
sys     0m0.000s


### Test1 ###

galileo dma andy-v4 9600 8n1:

root@galileo:~# time echo
"abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz01234
56
7
89abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz0123
45
6
789abcdefghijklmnopqrstuvwxyz0123456789" > /dev/ttyS0

real    0m0.209s
user    0m0.000s
sys     0m0.000s

galileo non-dma Linux 3.8.7 9600 8n1:

root@galileo:~# time echo
"abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz01234
56
7
89abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz0123
45
6
789abcdefghijklmnopqrstuvwxyz0123456789" > /dev/ttyS0

real    0m0.206s
user    0m0.000s
sys     0m0.000s


galileo non-dma tip-of-tree 9600 8n1:

root@galileo:~# time echo
"abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz01234
56
7
89abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz0123
45
6
789abcdefghijklmnopqrstuvwxyz0123456789" > /dev/ttyS0

real    0m0.199s
user    0m0.010s
sys     0m0.000s

-- 
Andy Shevchenko [off-list ref]
Intel Finland Oy