Uboot SPI uclass - question

[Moshe, Yaniv]

Hi,

So, I was thinking about the same solution of working with one frequency for the SPI, but then I saw this
comment in the "include/spi.h":

/* TODO(sjg at chromium.org): Remove this and use max_hz from struct spi_slave */
struct dm_spi_bus {
	uint max_hz;
};

So, I thought that maybe someone already has some progress about this problem...
In my case, the easy W/A was to just ignore the if that check if frequency is the same in the slave struct, and instead, I'm updating the speed for every change in slave.

I do think that working with one speed variable for the SPI is the right solution.

-Yaniv



-----Original Message-----
From: Rasmus Villemoes <rasmus.villemoes at prevas.dk> 
Sent: Sunday, November 22, 2020 11:22 PM
To: Moshe, Yaniv <yanivmo at amazon.com>; u-boot at lists.denx.de
Cc: sjg at chromium.org
Subject: RE: [EXTERNAL] Uboot SPI uclass - question

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On 02/11/2020 19.14, Moshe, Yaniv wrote:
> Hi Simon,
> Hope you're doing good.
>
> My name is Yaniv, and I have a question regarding an old commit in U-boot:
> commit 60e2809a848bccd3a8090d3f2237964670f2780c
> Author: Simon Glass <sjg at chromium.org<mailto:sjg at chromium.org>>
> Date:   Tue Feb 17 15:29:35 2015 -0700
>
>     dm: spi: Avoid setting the speed with every transfer
>
>     Only set the speed if it has changed from last time. Since the speed will
>     be 0 when the device is probed it will always be changed on the first
>     transfer after the device is probed.
>
>     Signed-off-by: Simon Glass 
> sjg at chromium.org<mailto:sjg at chromium.org>
>
>
> 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.
> 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.
>
> e.g:
> access flash with max-freq = X - > speed set access TPM with max-freq 
> =Y -> speed set access flash again, slave struct already configured, 
> no change between speed and slave->speed, -> speed stay the same as for TPM.
>
> Did I got it wrong? I'm trying to understand what am I missing...

No, you're reading it the same way I did:

https://lists.denx.de/pipermail/u-boot/2019-December/393854.html

I never followed up because I didn't actually have two different spi devices in play on the board I was working on at the time. But it's something that really should be fixed.

Rasmus