From owner-freebsd-embedded@freebsd.org Fri Apr 1 21:23:19 2016 Return-Path: Delivered-To: freebsd-embedded@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 652E7B00C89 for ; Fri, 1 Apr 2016 21:23:19 +0000 (UTC) (envelope-from brianfundakowskifeldman@gmail.com) Received: from mailman.ysv.freebsd.org (mailman.ysv.freebsd.org [IPv6:2001:1900:2254:206a::50:5]) by mx1.freebsd.org (Postfix) with ESMTP id 40729135D for ; Fri, 1 Apr 2016 21:23:19 +0000 (UTC) (envelope-from brianfundakowskifeldman@gmail.com) Received: by mailman.ysv.freebsd.org (Postfix) id 3FAE3B00C88; Fri, 1 Apr 2016 21:23:19 +0000 (UTC) Delivered-To: embedded@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 3F45BB00C87 for ; Fri, 1 Apr 2016 21:23:19 +0000 (UTC) (envelope-from brianfundakowskifeldman@gmail.com) Received: from mail-qg0-x233.google.com (mail-qg0-x233.google.com [IPv6:2607:f8b0:400d:c04::233]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id E62EC135C; Fri, 1 Apr 2016 21:23:18 +0000 (UTC) (envelope-from brianfundakowskifeldman@gmail.com) Received: by mail-qg0-x233.google.com with SMTP id f52so10611452qga.3; Fri, 01 Apr 2016 14:23:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=VOFgQCa4L/bT+OZGfXvkZ1CHQ/3NOK9ZQde5knij0Rg=; b=pnoztgaHtEvjIpe3/ApDm4+sXjYAAYu+58Uej0Pis//fJr3nWnecl4Fq1yMKtab0VR g3izw+R2ZDUBlgAenokojA2k/+bqw/nmVXXYiyEZNX+H5RJpBlwXmYypBynZ6PdjMCLW gpu057sGt5lKqcAFnivp1jvacOM0IIxE9gDg3GP3YHrE4gDtnnikAHRnvAu8U8eRFoZy tKUqpWds1dEVveL6JEsVLE5xzma75hb1LF3guxtXyrxOzmB8V6yEdfiuhT4/mCaf8DfG YY4JCu9+Wimavh2zRdPUcmcUPnP81J89gVROE6tNkXfKlJwg9UaKQ7RTqgDYLqHvkHV4 cXXQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=VOFgQCa4L/bT+OZGfXvkZ1CHQ/3NOK9ZQde5knij0Rg=; b=Viv+mFTljEe4Jlvv3WLQocOHeEJrcWLyVGqjunSnIPQPib4pY1ws+SJGVJABALnG1H L0JbYSH9t5YqqKadjcN0o3vijmjPQ1kRU/DqPQLm5AV58h9uTAxhmle8PdMABBRDV3AE hF0p9BMwUwLlw33684PpaYJ2uFVPGTE0egCtCWxfC4pF7SqMpZfHxvhD9ujcfrJAFMm+ FI9zv7devhEkn/msPxSslvsdtIGxs0GjmR/xVrlJWolilF87ae/+tmDjS2FNDtbvl/qS mpRWLePgw9K2KUgWVgTIvaHQgNn67iupCXuhnlFZ5qmx6KiGnPOhJN26/cwYmpJ9eCU2 4xKQ== X-Gm-Message-State: AD7BkJIRaw7/pPUng/NMA+RW22z9/4OG11XKETLH3ra/elz2BGxPfM5TIZEq+nqelywuIEfBNjk1HuTguk0rHw== X-Received: by 10.140.170.70 with SMTP id q67mr29615321qhq.8.1459545797695; Fri, 01 Apr 2016 14:23:17 -0700 (PDT) MIME-Version: 1.0 References: <20150817160423.GB3078@gmail.com> In-Reply-To: From: Brian Fundakowski Feldman Date: Fri, 01 Apr 2016 21:23:08 +0000 Message-ID: Subject: Re: spigen(4) SPI Generic IO interface -- need comments To: Adrian Chadd Cc: Warner Losh , Luiz Otavio O Souza , "freebsd-embedded@freebsd.org" Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.21 X-BeenThere: freebsd-embedded@freebsd.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: Dedicated and Embedded Systems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 01 Apr 2016 21:23:19 -0000 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 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 > 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 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 > >> 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 > >>> 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 > >>> > 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 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" > >> > >> > > >