From: Mark Brown <broonie@kernel.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jiada Wang <jiada_wang@mentor.com>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Shawn Guo <shawnguo@kernel.org>,
Sascha Hauer <kernel@pengutronix.de>,
Fabio Estevam <fabio.estevam@nxp.com>,
linux-spi <linux-spi@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH RFC 0/5] *** SPI Slave mode support ***
Date: Tue, 25 Apr 2017 11:31:13 +0100 [thread overview]
Message-ID: <20170425103113.lxpwoq6sbxvg3ihl@sirena.org.uk> (raw)
In-Reply-To: <CAMuHMdXa_O6RsqUciiNWQ0Zp6dniS47AUmPN9UWAWitP0csx=Q@mail.gmail.com>
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On Mon, Apr 24, 2017 at 12:55:21PM +0200, Geert Uytterhoeven wrote:
> On Fri, Apr 14, 2017 at 7:39 AM, Jiada Wang <jiada_wang@mentor.com> wrote:
> > 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?
That sounds like a mess... we *could* put the slave flag on the device
rather than the controller I guess but there's also going to need to be
something representing whatever avoids collisions on the bus somewhere.
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WARNING: multiple messages have this Message-ID (diff)
From: Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Geert Uytterhoeven <geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org>
Cc: Jiada Wang <jiada_wang-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org>,
Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>,
Shawn Guo <shawnguo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Sascha Hauer <kernel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>,
Fabio Estevam <fabio.estevam-3arQi8VN3Tc@public.gmane.org>,
linux-spi <linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org"
<linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>
Subject: Re: [PATCH RFC 0/5] *** SPI Slave mode support ***
Date: Tue, 25 Apr 2017 11:31:13 +0100 [thread overview]
Message-ID: <20170425103113.lxpwoq6sbxvg3ihl@sirena.org.uk> (raw)
In-Reply-To: <CAMuHMdXa_O6RsqUciiNWQ0Zp6dniS47AUmPN9UWAWitP0csx=Q@mail.gmail.com>
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On Mon, Apr 24, 2017 at 12:55:21PM +0200, Geert Uytterhoeven wrote:
> On Fri, Apr 14, 2017 at 7:39 AM, Jiada Wang <jiada_wang-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org> wrote:
> > 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?
That sounds like a mess... we *could* put the slave flag on the device
rather than the controller I guess but there's also going to need to be
something representing whatever avoids collisions on the bus somewhere.
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WARNING: multiple messages have this Message-ID (diff)
From: broonie@kernel.org (Mark Brown)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH RFC 0/5] *** SPI Slave mode support ***
Date: Tue, 25 Apr 2017 11:31:13 +0100 [thread overview]
Message-ID: <20170425103113.lxpwoq6sbxvg3ihl@sirena.org.uk> (raw)
In-Reply-To: <CAMuHMdXa_O6RsqUciiNWQ0Zp6dniS47AUmPN9UWAWitP0csx=Q@mail.gmail.com>
On Mon, Apr 24, 2017 at 12:55:21PM +0200, Geert Uytterhoeven wrote:
> On Fri, Apr 14, 2017 at 7:39 AM, Jiada Wang <jiada_wang@mentor.com> wrote:
> > 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?
That sounds like a mess... we *could* put the slave flag on the device
rather than the controller I guess but there's also going to need to be
something representing whatever avoids collisions on the bus somewhere.
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next prev parent reply other threads:[~2017-04-25 10:32 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-13 12:13 [PATCH RFC 0/5] *** SPI Slave mode support *** jiada_wang
2017-04-13 12:13 ` jiada_wang at mentor.com
2017-04-13 12:13 ` jiada_wang
2017-04-13 12:13 ` jiada_wang
2017-04-13 12:14 ` [PATCH RFC 1/5] spi: core: add support to work in Slave mode jiada_wang
2017-04-13 12:14 ` jiada_wang at mentor.com
2017-04-13 12:14 ` jiada_wang-nmGgyN9QBj3QT0dZR+AlfA
2017-04-13 12:14 ` jiada_wang-nmGgyN9QBj3QT0dZR+AlfA
2017-04-13 12:14 ` [PATCH RFC 2/5] spi: spidev: use different name for SPI controller slave mode device jiada_wang
2017-04-13 12:14 ` jiada_wang at mentor.com
2017-04-13 12:14 ` jiada_wang
2017-04-13 12:14 ` jiada_wang
2017-04-13 12:14 ` [PATCH RFC 3/5] spi: imx: add selection for iMX53 and iMX6 controller jiada_wang
2017-04-13 12:14 ` jiada_wang at mentor.com
2017-04-13 12:14 ` jiada_wang
2017-04-13 12:14 ` [PATCH RFC 4/5] ARM: dts: imx: change compatiblity for SPI controllers on imx53 later soc jiada_wang
2017-04-13 12:14 ` jiada_wang at mentor.com
2017-04-13 12:14 ` jiada_wang
2017-04-13 12:14 ` [PATCH RFC 5/5] spi: imx: Add support for SPI Slave mode for imx53 and imx6 chips jiada_wang
2017-04-13 12:14 ` jiada_wang at mentor.com
2017-04-13 12:14 ` jiada_wang
2017-04-13 12:59 ` [PATCH RFC 0/5] *** SPI Slave mode support *** Mark Brown
2017-04-13 12:59 ` Mark Brown
2017-04-13 12:59 ` Mark Brown
2017-04-13 19:47 ` Geert Uytterhoeven
2017-04-13 19:47 ` Geert Uytterhoeven
2017-04-13 19:47 ` Geert Uytterhoeven
2017-04-14 5:39 ` Jiada Wang
2017-04-14 5:39 ` Jiada Wang
2017-04-14 5:39 ` Jiada Wang
2017-04-24 10:55 ` Geert Uytterhoeven
2017-04-24 10:55 ` Geert Uytterhoeven
2017-04-24 10:55 ` Geert Uytterhoeven
2017-04-24 12:48 ` Jiada Wang
2017-04-24 12:48 ` Jiada Wang
2017-04-24 12:48 ` Jiada Wang
2017-04-24 13:10 ` Geert Uytterhoeven
2017-04-24 13:10 ` Geert Uytterhoeven
2017-04-24 13:10 ` Geert Uytterhoeven
2017-04-25 7:56 ` Jiada Wang
2017-04-25 7:56 ` Jiada Wang
2017-04-25 7:56 ` Jiada Wang
2017-04-25 8:07 ` Uwe Kleine-König
2017-04-25 8:07 ` Uwe Kleine-König
2017-04-25 8:07 ` Uwe Kleine-König
2017-04-25 8:09 ` Geert Uytterhoeven
2017-04-25 8:09 ` Geert Uytterhoeven
2017-04-25 8:09 ` Geert Uytterhoeven
2017-04-25 10:31 ` Mark Brown [this message]
2017-04-25 10:31 ` Mark Brown
2017-04-25 10:31 ` Mark Brown
2017-04-27 6:43 ` Jiada Wang
2017-04-27 6:43 ` Jiada Wang
2017-04-27 6:43 ` Jiada Wang
2017-05-24 17:29 ` Mark Brown
2017-05-24 17:29 ` Mark Brown
2017-05-24 17:29 ` Mark Brown
2017-05-29 12:01 ` Fabio Estevam
2017-05-29 12:01 ` Fabio Estevam
2017-05-29 12:01 ` Fabio Estevam
2017-05-30 2:53 ` Jiada Wang
2017-05-30 2:53 ` Jiada Wang
2017-05-30 2:53 ` Jiada Wang
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