>-----Original Message----- >From: Oikarinen Juuso (Nokia-D/Tampere) >Sent: 09 April, 2010 07:06 >To: Tereshonkov Roman (Nokia-D/Helsinki) >Cc: ext Grant Likely; spi-devel-general@lists.sourceforge.net; >Samuel Ortiz >Subject: RE: [PATCH 1/2] spi: Add support for dma_min_bytes >configuration. > >Hi, > >The wl1271 driver does not actually require this value to be adjustable >- i.e. the driver does not need to know the value. In fact, the wl1271 >does not know about DMA at all, instead the SPI controller driver makes >the choice on how to perform the transfer most optimally. > >So we - or the wl1271 driver - just need the selection between DMA and >PIO to be optimal in point of view of throughput and CPU load. The old >threshold value of 8 is far from optimal - something like 160-200 is in >the correct range. > >AFAIK performing the SPI transfer optimally should not affect other SPI >clients in a negative way, and AFAIK there are no other SPI clients in >Dali than the wl1271, so I guess this new threshold value could also be >hard-coded into the omap2_mcspi driver.
What about omap2 based projects which use the same driver? Roman > >-Juuso > >On Thu, 2010-04-08 at 17:25 +0200, Tereshonkov Roman (Nokia-D/Helsinki) >wrote: >> The others from wlan team need DMA_MIN_BYTES to be adjustable. >> Juuso can comment this. >> >> Just changing DMA_MIN_BYTES might influence on other spi devices >> controlled by omap2/3 spi controller driver. >> >> Roman >> >> >-----Original Message----- >> >From: glik...@secretlab.ca [mailto:glik...@secretlab.ca] On >> >Behalf Of ext Grant Likely >> >Sent: 08 April, 2010 18:09 >> >To: Tereshonkov Roman (Nokia-D/Helsinki) >> >Cc: spi-devel-general@lists.sourceforge.net; Samuel Ortiz >> >Subject: Re: [PATCH 1/2] spi: Add support for dma_min_bytes >> >configuration. >> > >> >On Thu, Apr 8, 2010 at 4:33 AM, ><roman.tereshon...@nokia.com> wrote: >> >> >> >> Hi, >> >> >> >> >> >>>-----Original Message----- >> >>>From: glik...@secretlab.ca [mailto:glik...@secretlab.ca] On >> >>>Behalf Of ext Grant Likely >> >>>Sent: 08 April, 2010 09:27 >> >>>To: Tereshonkov Roman (Nokia-D/Helsinki) >> >>>Cc: spi-devel-general@lists.sourceforge.net >> >>>Subject: Re: [PATCH 1/2] spi: Add support for dma_min_bytes >> >>>configuration. >> >>> >> >>>Hi Roman, >> >>> >> >>>On Tue, Apr 6, 2010 at 4:39 AM, Roman Tereshonkov >> >>><roman.tereshon...@nokia.com> wrote: >> >>>> This parameters defines the minimum number of bytes when >> >dma is used. >> >>>> >> >>>> Signed-off-by: Roman Tereshonkov <roman.tereshon...@nokia.com> >> >>> >> >>>The intent of this feature is... ? Your patch needs a better >> >>>description as to why it is needed; especially considering that it >> >>>changes common code. >> >>> >> >>>But, inferring from the code that is written, I can guess >what you're >> >>>trying to do, if not why. Why would spi_devices care what >> >the minimum >> >>>size of a DMA transfer is? The SPI bus driver is in a far better >> >>>position to make that determination. >> >>> >> >>>Also, since this essentially adds a new 'knob' for spi_devices to >> >>>twiddle, what is the expected behaviour for SPI bus >controllers that >> >>>don't support it? Is it a required feature for spi bus drivers to >> >>>implement if they support DMA? >> >> >> >> The spi transactions can be handled in two ways: dma and pio. >> >> For the best perfomance the minimun number of bytes when >dma is used >> >> can be found experimentaly and passed through the platform >> >board config files. >> >> >> >> Now I will talk about omap2/3 spi only. >> >> If the mentioned parameter is not set then the static default one >> >> is used (as it is nowdays). >> >> This exludes the patch influence on other spi devices controlled >> >> by the same omap2/3 spi master. >> >> >> >> I think you might be right. The better way would be to pass it >> >> through the controller_data field of the spi_board_info. >> >> Then I do not need to touch spi.h and spi.c. >> > >> >The question that must be asked, will this new optimization option >> >actually be profiled for most boards? Should it really be a >> >board-specific parameter? Or even an SoC specific parameter? Or to >> >be even more specific, do *you* have two different boards >that need a >> >different value for the minimum dma bytes? >> > >> >If the answer is no, then I recommend profiling your platform and >> >floating out a patch that changes the default value to what you find >> >is best. If there is no opposition to the value you choose, then >> >there is no need to make it a tunable until someone else comes along >> >who needs it to be something different. >> > >> >The current value of DMA_MIN_BYTES hasn't changed since the >driver was >> >first submitted. I suspect that it has not been optimized. > What does >> >Samuel have to say about it? >> > >> >g. >> > >> >> >> >> I will create a new patch. >> >> But now I wonder about patches syncronization. >> >> The first patch should go to linux-omap tree as it is for >> >arch/arm/plat-omap/include/plat/mcspi.h. >> >> The second patch applied after the first one is for >> >driver/spi/omap2_mcspi.h. >> >> Or can you handle both patches? >> >> >> >> >> >> Regards >> >> Roman >> > > > > ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ spi-devel-general mailing list spi-devel-general@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/spi-devel-general
