From: Vladimir Oltean <olteanv@gmail.com>
To: Michael Walle <michael@walle.cc>
Cc: Mark Brown <broonie@kernel.org>,
linux-spi@vger.kernel.org, lkml <linux-kernel@vger.kernel.org>,
Shawn Guo <shawnguo@kernel.org>, Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
devicetree@vger.kernel.org, Esben Haabendal <eha@deif.com>,
angelo@sysam.it, andrew.smirnov@gmail.com,
"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
Wei Chen <weic@nvidia.com>, Mohamed Hosny <mhosny@nvidia.com>,
peng.ma@nxp.com
Subject: Re: [PATCH 0/6] NXP DSPI bugfixes and support for LS1028A
Date: Mon, 9 Mar 2020 20:48:34 +0200 [thread overview]
Message-ID: <CA+h21hopP2XTx55iu_pG=xBx-TSPRBbdmoU7T2F0Gc9Qt=CsSQ@mail.gmail.com> (raw)
In-Reply-To: <6da04c9a17fa9e6259a462cb52312930@walle.cc>
On Mon, 9 Mar 2020 at 20:31, Michael Walle <michael@walle.cc> wrote:
>
> Am 2020-03-09 19:14, schrieb Vladimir Oltean:
> > On Mon, 9 Mar 2020 at 20:03, Michael Walle <michael@walle.cc> wrote:
> >> Am 2020-03-09 15:56, schrieb Vladimir Oltean:
> >> > From: Vladimir Oltean <vladimir.oltean@nxp.com>
> >> >
> >> > This series addresses a few issues that were missed during the previous
> >> > series "[PATCH 00/12] TCFQ to XSPI migration for NXP DSPI driver", on
> >> > SoCs other than LS1021A and LS1043A. DMA mode has been completely
> >> > broken
> >> > by that series, and XSPI mode never worked on little-endian
> >> > controllers.
> >> >
> >> > Then it introduces support for the LS1028A chip, whose compatible has
> >> > recently been documented here:
> >> >
> >> > https://lore.kernel.org/linux-devicetree/20200218171418.18297-1-michael@walle.cc/
> >>
> >> If it is not compatible with the LS1021A the second compatible string
> >> should be removed. Depending on the other remark about the endianess,
> >> it might still be compatible, though.
> >>
> >
> > Please feel free to remove it. I wasn't actually planning to add it in
> > the first place, but now it that it's there it doesn't really bother
> > anybody either.
>
> But it won't work if the endianess depends on the compatible string ;)
>
True.
> >>
> >> > The device tree for the LS1028A SoC is extended with DMA channels
> >> > definition, such that even though the default operating mode is XSPI,
> >> > one can simply change DSPI_XSPI_MODE to DSPI_DMA_MODE in the
> >> > devtype_data structure of the driver and use that instead.
> >>
> >> wouldn't it make more sense, to use DMA is the dma node is present
> >> in the device tree? otherwise use XSPI mode? I don't think it is
> >> really handy to change the mode inside the driver.
> >>
> >
> > Let's keep it simple. The driver should configure the hardware in the
> > most efficient and least buggy mode available. Right now that is XSPI.
> > The hardware description (aka the device tree) is a separate topic. If
> > there ever arises any situation where there are corner cases with XSPI
> > mode, it's good to have a fallback in the form of DMA mode, and not
> > have to worry about yet another problem (which is that there are 2
> > sets of device tree blobs in deployment).
>
> Point taken. But this is not how other drivers behave, which uses the
> DMA if its given in the device node.
>
Also true.
> Btw. do other SoCs perform better with DMA?
>
Not that I know of.
My general rule of thumb for this controller is: if it supports XSPI
then use that, otherwise use DMA. Luckily there is just one controller
that supports none of those, and that would be Coldfire, which uses
the braindead EOQ mode. I don't have the hardware to do testing on
that, but in principle if I did, I would have converted that as well
to the more functional but less efficient TCFQ mode (now removed).
> -michael
>
> > TL;DR: These DMA channels don't really bother anybody but you never
> > know when they might come in handy.
> >
> >> -michael
> >>
> >> >
> >> > For testing, benchmarking and debugging, the mikroBUS connector on the
> >> > LS1028A-RDB is made available via spidev.
> >> >
> >> > Vladimir Oltean (6):
> >> > spi: spi-fsl-dspi: Don't access reserved fields in SPI_MCR
> >> > spi: spi-fsl-dspi: Fix little endian access to PUSHR CMD and TXDATA
> >> > spi: spi-fsl-dspi: Fix oper_word_size of zero for DMA mode
> >> > spi: spi-fsl-dspi: Add support for LS1028A
> >> > arm64: dts: ls1028a: Specify the DMA channels for the DSPI
> >> > controllers
> >> > arm64: dts: ls1028a-rdb: Add a spidev node for the mikroBUS
> >> >
> >> > .../boot/dts/freescale/fsl-ls1028a-rdb.dts | 14 +++++
> >> > .../arm64/boot/dts/freescale/fsl-ls1028a.dtsi | 6 +++
> >> > drivers/spi/spi-fsl-dspi.c | 54 +++++++++++++++----
> >> > 3 files changed, 64 insertions(+), 10 deletions(-)
> >
> > Thanks,
> > -Vladimir
-Vladimir
next prev parent reply other threads:[~2020-03-09 18:48 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-09 14:56 [PATCH 0/6] NXP DSPI bugfixes and support for LS1028A Vladimir Oltean
2020-03-09 14:56 ` [PATCH 1/6] spi: spi-fsl-dspi: Don't access reserved fields in SPI_MCR Vladimir Oltean
[not found] ` <20200309145624.10026-2-olteanv-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2020-03-09 18:05 ` Michael Walle
[not found] ` <c35b3c34123b43b26204a2cf360e7ec1-QKn5cuLxLXY@public.gmane.org>
2020-03-09 18:09 ` Vladimir Oltean
2020-03-09 14:56 ` [PATCH 2/6] spi: spi-fsl-dspi: Fix little endian access to PUSHR CMD and TXDATA Vladimir Oltean
[not found] ` <20200309145624.10026-3-olteanv-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2020-03-09 17:59 ` Michael Walle
[not found] ` <d8e39e402328b962cdbc25316a27eac8-QKn5cuLxLXY@public.gmane.org>
2020-03-09 18:07 ` Vladimir Oltean
[not found] ` <CA+h21hp4vC1c00rCgZo_hwQz3cE4dLBHjcgTHvf-+fS9a9VfxQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2020-03-09 18:19 ` Michael Walle
[not found] ` <a709dc91aac9124ed37ac1e7fcb7e105-QKn5cuLxLXY@public.gmane.org>
2020-03-09 18:31 ` Vladimir Oltean
2020-03-09 14:56 ` [PATCH 4/6] spi: spi-fsl-dspi: Add support for LS1028A Vladimir Oltean
[not found] ` <20200309145624.10026-5-olteanv-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2020-03-09 18:38 ` Michael Walle
[not found] ` <02a2816d2f39bf621dfee543ed612ae0-QKn5cuLxLXY@public.gmane.org>
2020-03-09 18:51 ` Vladimir Oltean
[not found] ` <20200309145624.10026-1-olteanv-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2020-03-09 14:56 ` [PATCH 3/6] spi: spi-fsl-dspi: Fix oper_word_size of zero for DMA mode Vladimir Oltean
2020-03-09 14:56 ` [PATCH 5/6] arm64: dts: ls1028a: Specify the DMA channels for the DSPI controllers Vladimir Oltean
[not found] ` <20200309145624.10026-6-olteanv-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2020-03-09 19:06 ` Michael Walle
[not found] ` <83af52172a3cabd662de1ed9574e4247-QKn5cuLxLXY@public.gmane.org>
2020-03-09 19:59 ` Vladimir Oltean
2020-03-09 20:17 ` Michael Walle
2020-03-09 14:56 ` [PATCH 6/6] arm64: dts: ls1028a-rdb: Add a spidev node for the mikroBUS Vladimir Oltean
[not found] ` <20200309145624.10026-7-olteanv-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2020-03-09 18:35 ` Michael Walle
[not found] ` <f213388d924b63d0fe265a2d731647be-QKn5cuLxLXY@public.gmane.org>
2020-03-09 18:50 ` Vladimir Oltean
[not found] ` <CA+h21hqOhM9+k9cKXoA8coYpxNFWpgD+FjETeB6uWLbsfrx0uw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2020-03-09 18:58 ` Michael Walle
2020-03-09 18:03 ` [PATCH 0/6] NXP DSPI bugfixes and support for LS1028A Michael Walle
[not found] ` <f530a0740f34b2cf26a8055d4eae2527-QKn5cuLxLXY@public.gmane.org>
2020-03-09 18:14 ` Vladimir Oltean
2020-03-09 18:31 ` Michael Walle
2020-03-09 18:48 ` Vladimir Oltean [this message]
[not found] ` <CA+h21hopP2XTx55iu_pG=xBx-TSPRBbdmoU7T2F0Gc9Qt=CsSQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2020-03-09 18:59 ` Michael Walle
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