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Message-Id: <201506040103.09555.marex@denx.de>
Date: Thu, 4 Jun 2015 01:03:09 +0200
From: Marek Vasut <marex@...x.de>
To: Michal Suchanek <hramrach@...il.com>
Cc: Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
Russell King <linux@....linux.org.uk>,
Kukjin Kim <kgene@...nel.org>,
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Vinod Koul <vinod.koul@...el.com>,
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David Woodhouse <dwmw2@...radead.org>,
Brian Norris <computersforpeace@...il.com>,
Han Xu <han.xu@...escale.com>, Mark Brown <broonie@...nel.org>,
Geert Uytterhoeven <geert+renesas@...der.be>,
" Rafał Miłecki"
<zajec5@...il.com>, Alison Chaiken <alison_chaiken@...tor.com>,
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<beanhuo@...ron.com>, "grmoore@...era.com" <grmoore@...era.com>,
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linux-arm-kernel@...ts.infradead.org,
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Subject: Re: [PATCH 08/11] MTD: m25p80: Add option to limit SPI transfer size.
On Wednesday, June 03, 2015 at 11:26:41 PM, Michal Suchanek wrote:
> On sunxi the SPI controller currently does not have DMA support and fails
> any transfer larger than 63 bytes.
>
> On Exynos the pl330 DMA controller fails any transfer larger than 64kb
> when using slower speed like 40MHz and any transfer larger than 128bytes
> when running at 133MHz.
This smells more like some corruption of the data on the bus or something
even more obscure.
> The best thing is that in both cases the controller can just lock up and
> never finish potentially leaving the hardware in unusable state.
>
> So it is required that the m25p80 driver actively prevents doing
> transfers that are too large for the current driver state on a
> particular piece of hardware.
>
> Signed-off-by: Michal Suchanek <hramrach@...il.com>
>
> --
>
> Update commit message and documentation text.
> ---
> .../devicetree/bindings/mtd/jedec,spi-nor.txt | 6 ++++++
> drivers/mtd/devices/m25p80.c | 24
> ++++++++++++++++++++-- 2 files changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt
> b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt index
> 2bee681..4e63ae8 100644
> --- a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt
> +++ b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt
> @@ -19,6 +19,12 @@ Optional properties:
> all chips and support for it can not be detected at
> runtime. Refer to your chips' datasheet to check if this is supported by
> your chip.
> +- linux,max_tx_len : With some SPI controller drivers possible transfer
> size is + limited. This may be hardware or driver bug.
> + Transfer data in chunks no larger than this value. +
> Using this option may severely degrade performance and
> + possibly flash memory life when max_tx_len is
> smaller than + flash page size (typically 256 bytes)
Will we need similar patch for all other SPI slave drivers, like SPI NAND ?
Best regards,
Marek Vasut
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