* SPI controller bugfixes needed (full duplex + DMA, data corruption) @ 2008-11-15 22:22 David Brownell [not found] ` <200811151422.32748.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org> 0 siblings, 1 reply; 4+ messages in thread From: David Brownell @ 2008-11-15 22:22 UTC (permalink / raw) To: kernel-bIcnvbaLZ9MEGnE8C9+IrQ, Andrea Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f Hi, We recently turned up a bug in the pxa2xx SPI driver, which turns out to also be present in the spi_imx.c and au1550_spi.c drivers too. Briefly, full duplex transfers are allowed to share the same buffer (or partially overlap it), which means that the dma mapping operations must be done in a safe order: - first map the TX buffer, so cache data gets written to memory where the DMA will pick it up; - then map the RX buffer, so that cache entries (with soon-to-be-stale data) get removed. Doing it the other order, as is done with spi_imx and with au1550_spi, causes data corruption by discarding data from the cache *before* writing it to memory. If you can do it, it'd be good to see this fixed before the 2.6.28 kernel ships. - Dave p.s. Note that full duplex transfers became a bit more common after f9b90e39cbc5c4d6ef60022fd1f25d541df0aad1 merged (in the 2.6.28-rc0 merge frenzy). ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ ^ permalink raw reply [flat|nested] 4+ messages in thread
[parent not found: <200811151422.32748.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>]
* Re: SPI controller bugfixes needed (full duplex + DMA, data corruption) [not found] ` <200811151422.32748.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org> @ 2008-11-18 7:52 ` Sascha Hauer [not found] ` <20081118075215.GD9553-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> 0 siblings, 1 reply; 4+ messages in thread From: Sascha Hauer @ 2008-11-18 7:52 UTC (permalink / raw) To: David Brownell Cc: a.paterniani-03BXCEkGbFHYGGNLXY5/rw, AndreaPaterniani, kernel-bIcnvbaLZ9MEGnE8C9+IrQ, spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f Hi David, On Sat, Nov 15, 2008 at 02:22:32PM -0800, David Brownell wrote: > Hi, > > We recently turned up a bug in the pxa2xx SPI driver, which > turns out to also be present in the spi_imx.c and au1550_spi.c > drivers too. > > Briefly, full duplex transfers are allowed to share the > same buffer (or partially overlap it), which means that > the dma mapping operations must be done in a safe order: > > - first map the TX buffer, so cache data gets written > to memory where the DMA will pick it up; > > - then map the RX buffer, so that cache entries (with > soon-to-be-stale data) get removed. > > Doing it the other order, as is done with spi_imx and > with au1550_spi, causes data corruption by discarding > data from the cache *before* writing it to memory. > > If you can do it, it'd be good to see this fixed before > the 2.6.28 kernel ships. Hm, this is a non trivial fix. I don't have a MX1 based hardware with something on the SPI bus handy, so this would be a shot in the dark for me. I hope Andrea jumps in, otherwise we'll have to wait till the driver works on MX2. Sascha -- Pengutronix - Linux Solutions for Science and Industry Handelsregister: Amtsgericht Hildesheim, HRA 2686 Hannoversche Str. 2, 31134 Hildesheim, Germany Phone: +49-5121-206917-0 | Fax: +49-5121-206917-9 ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ ^ permalink raw reply [flat|nested] 4+ messages in thread
[parent not found: <20081118075215.GD9553-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]
* Re: SPI controller bugfixes needed (full duplex + DMA, data corruption) [not found] ` <20081118075215.GD9553-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> @ 2008-11-18 8:30 ` Andrea Paterniani [not found] ` <49227D0A.40506-03BXCEkGbFHYGGNLXY5/rw@public.gmane.org> 0 siblings, 1 reply; 4+ messages in thread From: Andrea Paterniani @ 2008-11-18 8:30 UTC (permalink / raw) To: Sascha Hauer Cc: David Brownell, spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f, kernel-bIcnvbaLZ9MEGnE8C9+IrQ I have an iMX1 based HW running kernel 2.6.25.8. I checked the patch and to seems to be ok (solves old problems on full duplex transfers). Regards, -- Andrea Sascha Hauer ha scritto: > Hi David, > > On Sat, Nov 15, 2008 at 02:22:32PM -0800, David Brownell wrote: > >> Hi, >> >> We recently turned up a bug in the pxa2xx SPI driver, which >> turns out to also be present in the spi_imx.c and au1550_spi.c >> drivers too. >> >> Briefly, full duplex transfers are allowed to share the >> same buffer (or partially overlap it), which means that >> the dma mapping operations must be done in a safe order: >> >> - first map the TX buffer, so cache data gets written >> to memory where the DMA will pick it up; >> >> - then map the RX buffer, so that cache entries (with >> soon-to-be-stale data) get removed. >> >> Doing it the other order, as is done with spi_imx and >> with au1550_spi, causes data corruption by discarding >> data from the cache *before* writing it to memory. >> >> If you can do it, it'd be good to see this fixed before >> the 2.6.28 kernel ships. >> > > Hm, this is a non trivial fix. I don't have a MX1 based hardware with > something on the SPI bus handy, so this would be a shot in the dark for > me. I hope Andrea jumps in, otherwise we'll have to wait till the driver > works on MX2. > > Sascha > > -- ------------------------------------------------------------------------ *Ing. Andrea Paterniani* *SWAPP* - Studio Professionale Via degli Abeti, 312 - 61100 Pesaro Tel 0721 24256 Fax 178 220 8730 a.paterniani-03BXCEkGbFHYGGNLXY5/rw@public.gmane.org www.swapp-eng.it <mailto:%0d%0aa.paterniani-03BXCEkGbFHYGGNLXY5/rw@public.gmane.org%0d%0awww.swapp-eng.it> ------------------------------------------------------------------------ ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ ^ permalink raw reply [flat|nested] 4+ messages in thread
[parent not found: <49227D0A.40506-03BXCEkGbFHYGGNLXY5/rw@public.gmane.org>]
* Re: SPI controller bugfixes needed (full duplex + DMA, data corruption) [not found] ` <49227D0A.40506-03BXCEkGbFHYGGNLXY5/rw@public.gmane.org> @ 2008-11-18 22:04 ` David Brownell 0 siblings, 0 replies; 4+ messages in thread From: David Brownell @ 2008-11-18 22:04 UTC (permalink / raw) To: Andrea Paterniani Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f, kernel-bIcnvbaLZ9MEGnE8C9+IrQ On Tuesday 18 November 2008, Andrea Paterniani wrote: > I have an iMX1 based HW running kernel 2.6.25.8. > I checked the patch and to seems to be ok (solves old problems on full > duplex transfers). Cool ... "solves old problems". ;) ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2008-11-18 22:04 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2008-11-15 22:22 SPI controller bugfixes needed (full duplex + DMA, data corruption) David Brownell [not found] ` <200811151422.32748.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org> 2008-11-18 7:52 ` Sascha Hauer [not found] ` <20081118075215.GD9553-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> 2008-11-18 8:30 ` Andrea Paterniani [not found] ` <49227D0A.40506-03BXCEkGbFHYGGNLXY5/rw@public.gmane.org> 2008-11-18 22:04 ` David Brownell
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).