On Tue, Mar 23, 2010 at 1:04 PM, Nori, Sekhar <nsek...@ti.com> wrote: > On Mon, Mar 22, 2010 at 20:36:13, Vladimir Pantelic wrote: >> Ben Gardiner wrote: >> > On Mon, Mar 22, 2010 at 10:20 AM, Vladimir Pantelic >> > <p...@nt.tu-darmstadt.de> wrote: >> >> Ben Gardiner wrote: >> >> >>> We noticed in the recent post by Sudhakar that it is somehow >> >>> 'supported' to handle DMA events on the DSP side. This makes a lot of >> >>> sense in retrospect and it spurs us to reconsider whether we can or >> >>> cannot access HW in general from the DSP side. >> >> >> >> Are you really really sure you need to have that? >> > >> > So I guess you agree with our current standing that all HW access >> > should be on the linux side then? >> >> no, but it much easier to do in on the side where all the infrastructure >> exists for it. I you must do it on the DSP, then do it, just think hard >> whether you really need that. > > If you do decide to access peripherals from DSP side, > OMAP-L1 SDK provides a DSP side drivers package as well. > > http://software-dl.ti.com/dsps/dsps_public_sw/sdo_sb/targetcontent/omap_l138/1_00/latest/index_FDS.html
Thanks for the useful link. >> >> So, the SPI data ends up in linux user space anyway. So are you really >> >> sure you cannot achieve your latencies with linux only? >> > >> > That's a good question. It is a bit of a hypothetical situation so I >> > can't say for sure in this case. I guess what I'm trying to get across >> > is that we would prefer to not write linux driver code since having >> > alot of custom Linux driver code has burned us in the past. We would >> > prefer to use existing code bases and drivers and work to make those >> > existing drivers stable with patches (that we post back upstream). >> >> err, but aren't linux spi drivers "existing" and/or "stable"? >> >> > This 'proxy driver' would be one that grabs the platform resources and >> > does nothing else then? Are there existing examples of proxy drivers >> > like this? >> >> no idea. >> > > AFAIK, there are no such proxy drivers. IMHO, it is much easier > to statically partition resources between the two cores rather > than create proxy drivers for resource sharing. So, if you want > to control a particular SPI instance from DSP, just don't register > the platform device for that SPI instance in your Linux board file. Thank you for offering your advice, Sekhar. One of our concerns with this approach -- or so we think -- is that the kernel power management would be free to supress the clock of that device. Could you comment on whether this is a concern and if it can be addressed in a static partition of resources? Best Regards, Ben Gardiner _______________________________________________ Davinci-linux-open-source mailing list Davinci-linux-open-source@linux.davincidsp.com http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source
