Date: Fri, 1 Apr 2016 17:06:53 -0700 From: Adrian Chadd <adrian.chadd@gmail.com> To: Brian Fundakowski Feldman <brianfundakowskifeldman@gmail.com> Cc: Warner Losh <imp@bsdimp.com>, Luiz Otavio O Souza <loos@freebsd.org>, "freebsd-embedded@freebsd.org" <embedded@freebsd.org> Subject: Re: spigen(4) SPI Generic IO interface -- need comments Message-ID: <CAJ-VmomtZJFX37LwFiytv_mG6PJtCiu98Kxpuv21k5sYduyXbw@mail.gmail.com> In-Reply-To: <CAEv1%2BOXeMNymXWGutT%2BcJCQ73NtZkH=6J9bCqOH4Le5DuB-BPg@mail.gmail.com> References: <CAEv1%2BOU4cFpMpeQGfnCP7L4Q_k18rOSOA9JBnKUa99DS5dFnWA@mail.gmail.com> <20150817160423.GB3078@gmail.com> <CAEv1%2BOUhSAJxxWAfW2GUFVw=H-_KOs2dGg2d7uhZnFbqsHE5Qw@mail.gmail.com> <CAEv1%2BOXe4w8hJXQu2MsoMLz6ixeG3hU3BmLZpssG15SaPd9JGw@mail.gmail.com> <CAJ-Vmom4qgXYL5eMPsnprvO4X7CES5ipAc0Z%2BsZtmMmF9K4Fqg@mail.gmail.com> <CAEv1%2BOUycUtCiQ9ZVxZjwAkvW0JiGi26tDKpvzD12P1wyEkeQw@mail.gmail.com> <CANCZdfo%2Bd2oA86iw_OXLros%2BBnVQZZqt2D_rWQMp-R6FNH5ueQ@mail.gmail.com> <CAEv1%2BOVvdEMx=pWX%2BaZ=PXb-tL=Ce1mZfP0CvXOnKTGTcYPTiA@mail.gmail.com> <CAJ-Vmo=raONYKNuixppFucP79KjuiL3ecmf8atuajKd=BfXdAg@mail.gmail.com> <CAEv1%2BOXeMNymXWGutT%2BcJCQ73NtZkH=6J9bCqOH4Le5DuB-BPg@mail.gmail.com>
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ok. So this just attaches to each spibus that is found, right? Can you share your example program(s)? I'd like to see how you used the mmap version. -adrian On 1 April 2016 at 14:23, Brian Fundakowski Feldman <brianfundakowskifeldman@gmail.com> wrote: > Great! I think the last part I wanted to have was a manpage that covered > configuring the device tree (dump, edit, rebuild) because that was fairly > non-obvious to me. I have only tested it on the RPi2 myself. > > > On Fri, Apr 1, 2016, 5:12 PM Adrian Chadd <adrian.chadd@gmail.com> wrote: >> >> hihi! >> >> ok, I'd now like to resurrect this - I'll take a look and see what's >> missing before we throw it into the tree. I'd like to use this for the >> atheros MIPS SPI stuff so i can more efficiently speak to an LCD. :P >> >> Thanks! >> >> >> -adrian >> >> >> On 22 August 2015 at 17:27, Brian Fundakowski Feldman >> <brianfundakowskifeldman@gmail.com> wrote: >> > You know, now you're making me wonder if the edge behavior shouldn't >> > also be >> > configurable per-spigen/per-transfer. Chip select polarity seems far too >> > dangerous to expose that way. The only SPI device I have lying around so >> > far >> > is an MCP3008. >> > >> > >> > On Sat, Aug 22, 2015, 8:17 PM Warner Losh <imp@bsdimp.com> wrote: >> >> >> >> I've worked on one set of flash that had simple commands for >> >> identifying >> >> it, which were clocked at one rate (slow, to be compatible with older >> >> members of the family), and other commands that were data transfer that >> >> were >> >> clocked faster to match the data coming from internal pipelines in the >> >> part. >> >> I don't know how common this arrangement is in the wild, though. >> >> >> >> And all of this is from memory of something I worked on maybe 10 years >> >> ago >> >> now, so I'm not sure how relevant it is today. I do know NAND flash >> >> chips >> >> have similar behavior, but those don't have a SPI bus. >> >> >> >> Warner >> >> >> >> >> >> On Sat, Aug 22, 2015 at 6:09 PM, Brian Fundakowski Feldman >> >> <brianfundakowskifeldman@gmail.com> wrote: >> >>> >> >>> That's something I want feedback on: are there scenarios where you >> >>> want >> >>> to >> >>> regularly vary the clock to a specific SPI device, as opposed to >> >>> varying >> >>> it >> >>> among several? It would be easy to add to the transfer ioctls if you >> >>> have >> >>> a >> >>> use case (for example, manual chip select control with more devices >> >>> than >> >>> chip select pins in your low-level SPI implementation.) Certainly >> >>> from a >> >>> runtime cost perspective it would be no burden. >> >>> >> >>> Thanks for taking a look! >> >>> -- >> >>> green >> >>> >> >>> On Sat, Aug 22, 2015, 5:55 PM Adrian Chadd <adrian.chadd@gmail.com> >> >>> wrote: >> >>> >> >>> > Hi! >> >>> > >> >>> > This looks cool! Is there any reason why the clock isn't per >> >>> > transaction? >> >>> > >> >>> > >> >>> > -a >> >>> > >> >>> > >> >>> > On 22 August 2015 at 11:23, Brian Fundakowski Feldman >> >>> > <brianfundakowskifeldman@gmail.com> wrote: >> >>> > > I've added a couple more features: >> >>> > > * clock adjustment via ioctl, independent per spigenN device >> >>> > > * mmap(2) support for very low latency >> >>> > > >> >>> > > On Tue, Aug 18, 2015 at 6:47 PM, Brian Fundakowski Feldman < >> >>> > > brianfundakowskifeldman@gmail.com> wrote: >> >>> > > >> >>> > >> On Mon, Aug 17, 2015 at 12:04 PM Tom Jones <jones@sdf.org> wrote: >> >>> > >> >> >>> > >>> On Mon, Aug 17, 2015 at 10:00:26AM -0400, Brian Fundakowski >> >>> > >>> Feldman >> >>> > wrote: >> >>> > >>> > I'm woefully out-of-practice with my kernel hackery (but still >> >>> > >>> > pretty >> >>> > >>> > proficient in jiggery-pokery) so I would like to get comments >> >>> > >>> > on >> >>> > >>> > a >> >>> > >>> little >> >>> > >>> > driver I just made for interfacing arbitrarily in userland >> >>> > >>> > with >> >>> > >>> > SPI >> >>> > >>> > components. The only thing I'm exposing is a /dev/spigenN >> >>> > >>> > node >> >>> > >>> > with >> >>> > a >> >>> > >>> > single transfer ioctl and I put together a test circuit and >> >>> > >>> > program >> >>> > >>> with an >> >>> > >>> > MCP3008 10-bit ADC IC to validate that it basically works, >> >>> > >>> > other >> >>> > >>> > than >> >>> > >>> the >> >>> > >>> > limitation that the transfers must be octet-multiply-sized, >> >>> > >>> > but I >> >>> > >>> haven't >> >>> > >>> > looked at the SoC's (I'm using a Raspberry Pi 2) data sheet to >> >>> > >>> > tell >> >>> > >>> whether >> >>> > >>> > that's just a limit on the spibus(4) interface or the Broadcom >> >>> > >>> > SPI >> >>> > >>> driver >> >>> > >>> > or the Broadcom SoC itself. >> >>> > >>> > >> >>> > >>> > I hit one snag in development where I simply called the ioctl >> >>> > >>> > wrong >> >>> > and >> >>> > >>> > found copyin(9) to page fault HARD if given a bogus user >> >>> > >>> > address >> >>> > >>> > to >> >>> > copy >> >>> > >>> > from, and panic the kernel. I can post up the test program if >> >>> > >>> > anyone >> >>> > >>> wants >> >>> > >>> > but it's very trivial: I just align the start bit and the >> >>> > >>> > command >> >>> > data >> >>> > >>> into >> >>> > >>> > the least significant bits of the first octet, shift it up two >> >>> > >>> positions so >> >>> > >>> > the NULs get clocked out as part of the command field, and >> >>> > >>> > provide >> >>> > two >> >>> > >>> > octets for the data field to retrieve back the 10-bit digital >> >>> > >>> > value. >> >>> > >>> >> >>> > >>> Oh, cool. >> >>> > >>> >> >>> > >>> I did the same earlier this year, have you seen[1]?. >> >>> > >>> >> >>> > >>> The FreeBSD i2c api is the same/very similar the linux >> >>> > >>> one[2][3]. >> >>> > >>> Have >> >>> > you >> >>> > >>> considered adding some of the ioctls[3] or the data structures >> >>> > >>> to >> >>> > >>> make >> >>> > it >> >>> > >>> easier to port code? >> >>> > >>> >> >>> > >>> [1]: >> >>> > >>> >> >>> > >> >>> > >> >>> > https://lists.freebsd.org/pipermail/freebsd-embedded/2015-April/002466.html >> >>> > >>> [2]: https://www.kernel.org/doc/Documentation/i2c/dev-interface >> >>> > >>> [3]: >> >>> > >>> >> >>> > >> >>> > >> >>> > https://www.freebsd.org/cgi/man.cgi?query=iic&apropos=0&sektion=0&manpath=FreeBSD+10.2-RELEASE&arch=default&format=html >> >>> > >>> [4]: https://www.kernel.org/doc/Documentation/spi/spidev >> >>> > >> >> >>> > >> >> >>> > >> I've iterated a bit on this to try to make some more sensible >> >>> > >> API, >> >>> > >> behaving reasonably about being able to set the SPI clock speed. >> >>> > >> I'm >> >>> > going >> >>> > >> to implement an mmap handler so I can have my low-latency >> >>> > >> operation >> >>> > mode, >> >>> > >> as well. I don't like the Linux APIs one bit because it's just >> >>> > >> not >> >>> > safe to >> >>> > >> allow all those configuration changes on a per-transfer basis... >> >>> > >> >> >>> > >> Moving this to -embedded because it's more apt than -hackers. >> >>> > >> >> >>> > > >> >>> > > _______________________________________________ >> >>> > > freebsd-embedded@freebsd.org mailing list >> >>> > > https://lists.freebsd.org/mailman/listinfo/freebsd-embedded >> >>> > > To unsubscribe, send any mail to " >> >>> > freebsd-embedded-unsubscribe@freebsd.org" >> >>> > >> >>> _______________________________________________ >> >>> freebsd-embedded@freebsd.org mailing list >> >>> https://lists.freebsd.org/mailman/listinfo/freebsd-embedded >> >>> To unsubscribe, send any mail to >> >>> "freebsd-embedded-unsubscribe@freebsd.org" >> >> >> >> >> >
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