I realized that in my BIOS settings, I was in ACPI mode. Do I need to be in PCI mode to use a board file? What does that ACPI-PCI switch in the BIOS do? thanks for all the help
On Mon, Jan 26, 2015 at 11:35 PM, Darren Hart <[email protected]> wrote: > The SPI bus controlled by the pxa2xx driver is on the LPSS, which, yes, > corresponds to the Low Power IO Controller in that block diagram. > > On 1/26/15, 10:38 PM, "Kevin Shelton" <[email protected]> wrote: > >>Thanks John and Darren. I will play with spid_devtest and have >>reached out to [email protected]. >> >>A minnowmax-specific question: In the Baytrail block diagram at >>http://media.bestofmicro.com/Y/3/400395/original/bay-trail-soc.jpg >>does the Marvell pxa27x correspond to the "Low Power IO Controller"? >> >>On Mon, Jan 26, 2015 at 6:33 PM, Darren Hart <[email protected]> >>wrote: >>> On 1/26/15, 5:52 PM, "John Hawley" <[email protected]> wrote: >>> >>>>On 01/26/2015 05:47 PM, Kevin Shelton wrote: >>>>> >>>>> >>>>> On Fri, Jan 23, 2015 at 2:41 PM, John Hawley <[email protected] >>>>> <mailto:[email protected]>> wrote: >>>>> >>>>> > I saw the thread 'Adding an SPI device to the Minnowboard' from >>>>>late >>>>> > 2013 and 'SPI support on minnowboard v1' from Aug 2014. >>>>> > >>>>> > Darren Hart notes: >>>>> > Ultimately we want to do things like this without board files by >>>>>using >>>>> > the _DSD mechanisms introduced by the ACPI 5.1 specification >>>>>last >>>>>week >>>>> > >>>>> > I just wanted to confirm the ACPI mechanism is not the >>>>>recommended way >>>>> > yet, and that using low-speed-spidev.c as a template is still >>>>>the >>>>>way to go. >>>>> >>>>> The answer to that will depend on what kernel you are intending to >>>>> target. Kernel's with ACPI 5.1 _DSD support, I think you'd want >>>>>to >>>>>push >>>>> on that. Older kernels without that, likely spidev or a more >>>>>targeted >>>>> driver. >>>>> >>>>> >>>>> Currently, I am targeting 3.17. 3.17 does not have ACPI 5.1 _DSD >>>>> support, correct? >>>> >>>>Off the top of my head that came in in 3.18, so yes that's correct. >>> >>> 3.19 iirc. >>> >>> Also, using _DSD required a firmware change, or at least a DSDT update. >>> >>>> >>>>> > Additional q: >>>>> > How do you tell the SPI controller that you have an active-high >>>>>instead >>>>> > of the usual active-low device? Is it correct to do a bitwise >>>>>or >>>>>with >>>>> > SPI_CS_HIGH (0x4) with your SPI_MODE in your spi_board_info >>>>>struct, like: >>>>> > .mode = SPI_MODE_0 | SPI_CS_HIGH >>>>> >>>>> That should work, but take my statement with a grain of salt as I >>>>> haven't tried it with a device. >>>>> >>>>> >>>>> It seems to have no effect that I can discern. Pin 5 idles at 3.3V >>>>> whether I have >>>>> .mode = SPI_MODE_3 | SPI_CS_HIGH >>>>> -or- >>>>> .mode = SPI_MODE_3 >>>>> >>>>> I threw in a >>>>> pr_info("SPI mode=%i\n", cod_spi_board_info.mode); >>>>> to sanity check that I am setting the mode to what I think I am (3 or >>>>>7). >>>>> >>>>> Any debugging ideas? >>>>> What is the best way to learn more about the SPI master? It's built >>>>> into the CPU, correct? >>>>> This smells in the ballpark of >>>>> relatedness: >>>>>http://lists.infradead.org/pipermail/linux-arm-kernel/2014-June/263467. >>>>>ht >>>>>ml >>>>> I don't grok that patch, but I confirmed my version of pxa2xx.c in my >>>>> 3.17 tree appears to contain that change. >>>> >>>>The SPI interface is indeed built into the CPU. It's the pxa2xx core, >>>>which it looks like you've found. I'd have to punt to someone else, as >>>>I'll admit, I don't know the SPI code well enough to say what's going >>>>on. I've CC'ed Darren Hart, he might know who to check with next. >>> >>> Those are some very specific SPI usage questions that I don't know the >>> answer to off the top of my head. To find out, I would: >>> >>> 1) Search for other drivers in tree and externally that use active-high >>> >>> First hit looks interesting: >>> https://www.kernel.org/doc/Documentation/spi/spidev_test.c >>> >>> >>> 2) Lookup the right mailing lists for SPI Linux kernel development and >>>ask >>> the same question there >>> >>> -- >>> Darren Hart >>> Intel Open Source Technology Center >>> >>> >>> >>> _______________________________________________ >>> elinux-MinnowBoard mailing list >>> [email protected] >>> http://lists.elinux.org/mailman/listinfo/elinux-minnowboard >> > > > -- > Darren Hart > Intel Open Source Technology Center > > > _______________________________________________ elinux-MinnowBoard mailing list [email protected] http://lists.elinux.org/mailman/listinfo/elinux-minnowboard
