Re: [PATCH v5 00/11] serial: 8250: split LPSS to 8250_lpss, enable DMA on Quark

Bryan O'Donoghue
2016-05-19T01:18:59Z

On Thu, 2016-05-12 at 18:06 +0300, Andy Shevchenko wrote:
> On Fri, 2016-05-06 at 18:17 +0300, Andy Shevchenko wrote:
> > 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.

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
"abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz01234567
89abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz0123456
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
"abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz01234567
89abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz0123456
789abcdefghijklmnopqrstuvwxyz0123456789" > /dev/ttyS0

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

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

root@galileo:~# time echo
"abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz01234567
89abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz0123456
789abcdefghijklmnopqrstuvwxyz0123456789" > /dev/ttyS0

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

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bod