linux-kernel - Re: [PATCH 00/10] spi: Add driver to support AMD eSPI controller

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Message-ID: <c239f4ce-98d3-4896-989c-3f1e4e5ad0d1@amd.com>
Date: Wed, 2 Apr 2025 17:13:17 +0530
From: "Rangoju, Raju" <raju.rangoju@....com>
To: Mark Brown <broonie@...nel.org>
Cc: linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
 krishnamoorthi.m@....com, akshata.mukundshetty@....com
Subject: Re: [PATCH 00/10] spi: Add driver to support AMD eSPI controller



On 3/26/2025 4:35 PM, Mark Brown wrote:
> On Wed, Mar 26, 2025 at 03:25:21PM +0530, Rangoju, Raju wrote:
>> On 3/17/2025 7:44 PM, Mark Brown wrote:
> 
>>> I see nothing in this series that registers a SPI controller with the
>>> SPI core.  You need to use the standard frameworks the kernel offers to
>>> provide standard functionality.
> 
>> The AMD SPI controller hardware has only the chip select line enabled, which
>> is connected to the EC slave in AMD EMB platforms. Currently, there is no
>> support from the slave device to register as an SPI slave device with the
>> SPI framework and provide SPI communication.
> 
>> For this reason, the AMD eSPI driver is designed to handle device
>> initialization itself and provide a character device file as an interface
>> with user space for dynamic interaction and configurations.
> 
> If you want to ignore the SPI subsystem and just write a driver for your
> embedded controller then you should put the driver in the subsystem or
> subsystems for that embedded controller (possibly MFD if it does a bunch
> of things), not SPI.  Even if there is no flexibility you may still want
> to have the controller side in the SPI subsystem in order to help with
> reuse with different controller/EC combinations but if you're going that
> way you need to use the SPI subsystem.

Thanks for the suggestions Mark. We will rework on this.