linux-kernel - Re: [PATCH v5 00/11] serial: 8250: split LPSS to 8250

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Date:	Tue, 24 May 2016 20:37:28 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Bryan O'Donoghue <pure.logic@...us-software.ie>,
	Peter Hurley <peter@...leysoftware.com>,
	linux-serial@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
	linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	ismo.puustinen@...el.com,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Subject: Re: [PATCH v5 00/11] serial: 8250: split LPSS to 8250_lpss, enable
 DMA on Quark

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

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?

> 
> 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@...ileo:~# 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@...ileo:~# time echo "abcdefghijklmnopqrstuvwxyz0123456789" >
> /dev/ttyS0
> 
> real    0m0.051s
> user    0m0.000s
> sys     0m0.000s
> 
> galileo non-dma tip-of-tree 9600 8n1:
> 
> root@...ileo:~# time echo "abcdefghijklmnopqrstuvwxyz0123456789" >
> /dev/ttyS0
> 
> real    0m0.048s
> user    0m0.000s
> sys     0m0.000s
> 
> 
> ### Test1 ###
> 
> galileo dma andy-v4 9600 8n1:
> 
> root@...ileo:~# time echo
> "abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz0123456
> 7
> 89abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz012345
> 6
> 789abcdefghijklmnopqrstuvwxyz0123456789" > /dev/ttyS0
> 
> real    0m0.209s
> user    0m0.000s
> sys     0m0.000s
> 
> galileo non-dma Linux 3.8.7 9600 8n1:
> 
> root@...ileo:~# time echo
> "abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz0123456
> 7
> 89abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz012345
> 6
> 789abcdefghijklmnopqrstuvwxyz0123456789" > /dev/ttyS0
> 
> real    0m0.206s
> user    0m0.000s
> sys     0m0.000s
> 
> 
> galileo non-dma tip-of-tree 9600 8n1:
> 
> root@...ileo:~# time echo
> "abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz0123456
> 7
> 89abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz012345
> 6
> 789abcdefghijklmnopqrstuvwxyz0123456789" > /dev/ttyS0
> 
> real    0m0.199s
> user    0m0.010s
> sys     0m0.000s
> 
> 
> ---
> bod

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy