From: Michael Walle <michael-QKn5cuLxLXY@public.gmane.org>
To: Vladimir Oltean <olteanv-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
lkml <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Shawn Guo <shawnguo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>,
devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Esben Haabendal <eha-/iRVSOupHO4@public.gmane.org>,
angelo-BIYBQhTR83Y@public.gmane.org,
andrew.smirnov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
"Gustavo A. R. Silva"
<gustavo-L1vi/lXTdts+Va1GwOuvDg@public.gmane.org>,
Wei Chen <weic-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
Mohamed Hosny <mhosny-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
peng.ma-3arQi8VN3Tc@public.gmane.org
Subject: Re: [PATCH 0/6] NXP DSPI bugfixes and support for LS1028A
Date: Mon, 09 Mar 2020 19:59:37 +0100 [thread overview]
Message-ID: <0b1da58b9d34b6bdb7617f5340d341ac@walle.cc> (raw)
In-Reply-To: <CA+h21hopP2XTx55iu_pG=xBx-TSPRBbdmoU7T2F0Gc9Qt=CsSQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
Am 2020-03-09 19:48, schrieb Vladimir Oltean:
> On Mon, 9 Mar 2020 at 20:31, Michael Walle <michael-QKn5cuLxLXY@public.gmane.org> wrote:
>>
>> Am 2020-03-09 19:14, schrieb Vladimir Oltean:
>> > On Mon, 9 Mar 2020 at 20:03, Michael Walle <michael-QKn5cuLxLXY@public.gmane.org> wrote:
>> >> Am 2020-03-09 15:56, schrieb Vladimir Oltean:
>> >> > From: Vladimir Oltean <vladimir.oltean-3arQi8VN3Tc@public.gmane.org>
>> >> >
>> >> > 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-QKn5cuLxLXY@public.gmane.org/
>> >>
>> >> 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.
So another reason to not have the endianess (read the CMD/TX register
offset)
depends on the compatible string. Because then it should work also with
the
ls1021a version, correct?
-michael
>
>> >>
>> >> > 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
prev parent reply other threads:[~2020-03-09 18:59 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
[not found] ` <CA+h21hopP2XTx55iu_pG=xBx-TSPRBbdmoU7T2F0Gc9Qt=CsSQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2020-03-09 18:59 ` Michael Walle [this message]
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