linux-kernel - Re: [PATCH 01/16] docs: Add documentation for MHI bus

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Date:   Thu, 23 Jan 2020 13:58:22 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     gregkh <gregkh@...uxfoundation.org>, smohanad@...eaurora.org,
        Jeffrey Hugo <jhugo@...eaurora.org>,
        Kalle Valo <kvalo@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        hemantk@...eaurora.org,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH 01/16] docs: Add documentation for MHI bus

On Thu, Jan 23, 2020 at 12:18 PM Manivannan Sadhasivam
<manivannan.sadhasivam@...aro.org> wrote:
> +============
> +MHI Topology
> +============
> +
> +This document provides information about the MHI topology modeling and
> +representation in the kernel.
> +
> +MHI Controller
> +--------------
> +
> +MHI controller driver manages the interaction with the MHI client devices
> +such as the external modems and WiFi chipsets. It is also the MHI bus master
> +which is in charge of managing the physical link between the host and device.
> +It is however not involved in the actual data transfer as the data transfer
> +is taken care by the physical bus such as PCIe. Each controller driver exposes
> +channels and events based on the client device type.
> +
> +Below are the roles of the MHI controller driver:
> +
> +* Turns on the physical bus and establishes the link to the device
> +* Configures IRQs, SMMU, and IOMEM
> +* Allocates struct mhi_controller and registers with the MHI bus framework
> +  with channel and event configurations using mhi_register_controller.
> +* Initiates power on and shutdown sequence
> +* Initiates suspend and resume power management operations of the device.

I don't see any callers of mhi_register_controller(). Did I just miss it or did
you not post one? I'm particularly interested in where the configuration comes
from, is this hardcoded in the driver, or parsed from firmware or from registers
in the hardware itself?

        Arnd