From: marex@denx•de (Marek Vasut)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 08/11] MTD: m25p80: Add option to limit SPI transfer size.
Date: Wed, 22 Jul 2015 09:33:19 +0200 [thread overview]
Message-ID: <201507220933.19752.marex@denx.de> (raw)
In-Reply-To: <CAOMqctQH4MnKMthOnuPgB-A5k6PCOAmhwHzJfn7gE3R4w8bufg@mail.gmail.com>
On Wednesday, July 22, 2015 at 09:30:54 AM, Michal Suchanek wrote:
> On 22 July 2015 at 06:49, Vinod Koul <vinod.koul@intel•com> wrote:
> > On Tue, Jul 21, 2015 at 10:14:11AM +0200, Michal Suchanek wrote:
> >> > Or alternatively we could publish the limitations of the channel using
> >> > capabilities so SPI knows I have a dmaengine channel and it can
> >> > transfer max N length transfers so would be able to break rather than
> >> > guessing it or coding in DT. Yes it may come from DT but that should
> >> > be dmaengine driver rather than client driver :)
> >> >
> >> > This can be done by dma_get_slave_caps(chan, &caps)
> >> >
> >> > And we add max_length as one more parameter to existing set
> >> >
> >> > Also all this could be handled in generic SPI-dmaengine layer so that
> >> > individual drivers don't have to code it in
> >> >
> >> > Let me know if this idea is okay, I can push the dmaengine bits...
> >>
> >> It would be ok if there was a fixed limit. However, the limit depends
> >> on SPI slave settings. Presumably for other buses using the dmaengine
> >> the limit would depend on the bus or slave settings as well. I do not
> >> see a sane way of passing this all the way to the dmaengine driver.
> >
> > I don't see why this should be client (SPI) dependent. The max length
> > supported is a dmaengine constraint, typically flowing from max
> > blocks/length it can transfer. Know this limit can allow clients to split
> > transfers.
>
> In practice on the board I have the maximum transfer length before it
> fails depends on SPI bus speed which is set up per slave. I did not
> try searching the space of possible settings thorougly and settled for
> a setting that gives reasonable speed and transfer length.
This looks more like a signal integrity issue though.
> However, if this was not tied to the particular slave setting picked
> in the current DT a formula would be needed that translates arbitrary
> client settings to transfer size limit and there would be need to
> somehow get the client settings to the formula in the dmaengine
> driver.
>
> Thanks
>
> Michal
Best regards,
Marek Vasut
next prev parent reply other threads:[~2015-07-22 7:33 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-03 21:26 [PATCH 00/11] Enable access to SPI NOR flash on Samsung Snow board Michal Suchanek
2015-06-03 21:26 ` [PATCH 01/11] ARM: dt: Add SPI CS " Michal Suchanek
2015-06-04 2:05 ` Krzysztof Kozlowski
2015-06-04 6:52 ` Javier Martinez Canillas
2015-06-03 21:26 ` [PATCH 03/11] mtd: add debug prints to mtdpart partition parser Michal Suchanek
2015-06-03 21:26 ` [PATCH 05/11] mtd: mtdpart: Do not fail mtd probe when parsing partitions fails Michal Suchanek
2015-06-03 21:26 ` [PATCH 04/11] mtd: ofpart: do not fail probe when no partitions exist Michal Suchanek
2015-06-03 22:58 ` Marek Vasut
2015-06-04 4:54 ` Michal Suchanek
2015-06-04 15:28 ` Marek Vasut
2015-06-04 15:40 ` Michal Suchanek
2015-06-05 14:13 ` Marek Vasut
2015-06-23 18:26 ` Brian Norris
2015-06-03 21:26 ` [PATCH 02/11] mtd: spi-nor: Add GD25LQ32C 1.8V SPI NOR flash ID Michal Suchanek
2015-06-03 21:26 ` [PATCH 07/11] mtd: spi-nor: rework write loop Michal Suchanek
2015-06-03 21:26 ` [PATCH 08/11] MTD: m25p80: Add option to limit SPI transfer size Michal Suchanek
2015-06-03 23:03 ` Marek Vasut
2015-06-04 4:31 ` Michal Suchanek
2015-06-04 15:15 ` Marek Vasut
2015-06-04 6:42 ` Geert Uytterhoeven
2015-06-04 8:31 ` Michal Suchanek
2015-06-04 17:15 ` Richard Cochran
2015-07-15 9:45 ` Michal Suchanek
2015-07-15 11:52 ` Marek Vasut
2015-07-15 15:59 ` Brian Norris
2015-07-15 17:15 ` Marek Vasut
2015-07-16 1:19 ` Brian Norris
2015-07-16 1:44 ` Marek Vasut
2015-07-19 19:01 ` Michal Suchanek
2015-07-21 4:29 ` Vinod Koul
2015-07-21 8:14 ` Michal Suchanek
2015-07-22 4:49 ` Vinod Koul
2015-07-22 7:30 ` Michal Suchanek
2015-07-22 7:33 ` Marek Vasut [this message]
2015-07-22 7:45 ` Michal Suchanek
2015-07-22 7:58 ` Marek Vasut
2015-07-22 8:18 ` Michal Suchanek
2015-07-22 8:24 ` Marek Vasut
2015-07-22 8:38 ` Michal Suchanek
2015-07-22 9:01 ` Marek Vasut
2015-07-23 16:46 ` Michal Suchanek
2015-07-23 17:03 ` Michal Suchanek
2015-07-24 8:34 ` Marek Vasut
2015-07-24 11:20 ` Michal Suchanek
2015-07-27 9:46 ` Michal Suchanek
2015-07-27 17:43 ` Marek Vasut
2015-07-27 20:43 ` Michal Suchanek
2015-07-30 11:24 ` Marek Vasut
2015-07-30 12:18 ` Michal Suchanek
2015-07-30 12:33 ` Marek Vasut
2015-06-03 21:26 ` [PATCH 09/11] dma: pl330: fix wording in mcbufsz message Michal Suchanek
2015-06-04 2:10 ` Krzysztof Kozlowski
2015-06-08 11:07 ` Vinod Koul
2015-06-03 21:26 ` [PATCH 06/11] mtd: spi-nor: rework spi nor read and write Michal Suchanek
2015-06-03 21:26 ` [PATCH 10/11] spi: add more debug prints in s3c64xx Michal Suchanek
2015-06-03 23:04 ` Marek Vasut
2015-06-04 9:16 ` Mark Brown
2015-06-04 9:30 ` Geert Uytterhoeven
2015-06-04 9:42 ` Mark Brown
2015-06-04 9:33 ` Michal Suchanek
2015-06-04 10:26 ` Mark Brown
2015-06-04 10:52 ` Michal Suchanek
2015-06-04 10:56 ` Mark Brown
2015-06-03 21:26 ` [PATCH 11/11] dt: Exynos: add Snow SPI NOR node Michal Suchanek
2015-06-04 2:04 ` Krzysztof Kozlowski
2015-06-04 15:20 ` Marek Vasut
2015-06-17 12:19 ` Pavel Machek
2015-06-03 22:53 ` [PATCH 00/11] Enable access to SPI NOR flash on Samsung Snow board Marek Vasut
2015-06-04 4:21 ` Michal Suchanek
2015-06-04 15:29 ` Marek Vasut
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=201507220933.19752.marex@denx.de \
--to=marex@denx$(echo .)de \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox