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

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Message-ID: <55ad37f1-0fbe-4a83-a998-80f2fd94a883@amd.com>
Date: Wed, 26 Mar 2025 15:25:21 +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 3/17/2025 7:44 PM, Mark Brown wrote:

Hi Mark,

Thanks for reviewing the patch and apologies for delayed response.

> On Fri, Mar 14, 2025 at 12:04:30AM +0530, Raju Rangoju wrote:
>> The eSPI protocol serves as a communication interface between the main
>> processor and peripheral devices in computer systems. It offers several
>> advantages over the traditional LPC bus, including higher data transfer
>> rates, increased scalability and improved system management capabilities.
>> The eSPI protocol supports multiple channels, each serving a specific
>> purpose in the communication process.
> 
> 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.