From mboxrd@z Thu Jan 1 00:00:00 1970 From: Geert Uytterhoeven Subject: Re: [PATCH RFC 0/5] *** SPI Slave mode support *** Date: Mon, 24 Apr 2017 12:55:21 +0200 Message-ID: References: <1492085644-4195-1-git-send-email-jiada_wang@mentor.com> <20170413125929.dygodgj6c35ydh5p@sirena.org.uk> <58F06092.9080409@mentor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: Mark Brown , Rob Herring , Mark Rutland , Shawn Guo , Sascha Hauer , Fabio Estevam , linux-spi , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" To: Jiada Wang Return-path: In-Reply-To: <58F06092.9080409-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org> Sender: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Hi Jiada, On Fri, Apr 14, 2017 at 7:39 AM, Jiada Wang wrote: > On 04/13/2017 12:47 PM, Geert Uytterhoeven wrote: >> On Thu, Apr 13, 2017 at 2:59 PM, Mark Brown wrote: >>> On Thu, Apr 13, 2017 at 05:13:59AM -0700, jiada_wang-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org wrote: >>>> From: Jiada Wang >>>> >>>> v1: >>>> add Slave mode support in SPI core >>>> spidev create slave device when SPI controller work in slave mode >>>> spi-imx support to work in slave mode >>> >>> Adding Geert who also had a series doing this in progress that was >>> getting very near to being merged. >> >> Thank you! >> >> Actually my plan is to fix the last remaining issues and resubmit for >> v4.13. > > I noticed your patch set for SPI slave support, > (I am sure you can find out some of the change > in this patch set is based on your work). > we have similar requirement to add slave mode support to ecspi IP on imx6 > Soc. > > Our use case is to use spidev as an interface to communicate with external > SPI master devices. > meanwhile the SPI bus controller can also act as master device to send data > to other > SPI slave devices on the board. That sounds a bit hackish to me. SPI was never meant to be a multi-master bus. While it can be done, you will need external synchronization (signals) to avoid conflicts between the SPI masters. > I found in your implementation, SPI bus controller is limited to either work > in master mode or > slave mode, is there any reasoning to not configure SPI mode based on SPI > devices use case? If you really need both master and slave support, you can use 2 subnodes in DT, the first representing the master, the second the slave. Mark, what's your opinion about this? Thanks! Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html