Uboot SPI uclass - question

[Simon Glass]

Hi Yaniv,

On Mon, 2 Nov 2020 at 11:14, Moshe, Yaniv <yanivmo at amazon.com> wrote:
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> Hi Simon,
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> Hope you’re doing good.
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>
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> My name is Yaniv, and I have a question regarding an old commit in U-boot:
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> commit 60e2809a848bccd3a8090d3f2237964670f2780c
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> Author: Simon Glass <sjg at chromium.org>
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> Date:   Tue Feb 17 15:29:35 2015 -0700
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>
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>     dm: spi: Avoid setting the speed with every transfer
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>
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>     Only set the speed if it has changed from last time. Since the speed will
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>     be 0 when the device is probed it will always be changed on the first
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>     transfer after the device is probed.
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>
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>     Signed-off-by: Simon Glass sjg at chromium.org
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> As far as I understand it, each SPI slave has its own struct. So, when we will use the device for the first time, we will set the speed.
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> But, if we’re jumping between different slaves, the slaves structs were already configured at the first time, and since then there won’t be any future speed setting.
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>
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> e.g:
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> access flash with max-freq = X - > speed set
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> access TPM with max-freq =Y -> speed set
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> access flash again, slave struct already configured, no change between speed and slave->speed, -> speed stay the same as for TPM.
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>
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> Did I got it wrong? I’m trying to understand what am I missing…

Yes I think you are right. I think we need to have a single speed for
the SPI bus and check against that instead. It could be stored in
dm_spi_bus perhaps?

Regards,
Simon