linux-kernel - Re: [PATCH v3 1/3] bus: mhi: host: Add sysfs entry to force device to enter EDL

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Message-ID: <20240415115616.GF7537@thinkpad>
Date: Mon, 15 Apr 2024 17:26:16 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Qiang Yu <quic_qianyu@...cinc.com>
Cc: quic_jhugo@...cinc.com, mhi@...ts.linux.dev,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	quic_cang@...cinc.com, quic_mrana@...cinc.com
Subject: Re: [PATCH v3 1/3] bus: mhi: host: Add sysfs entry to force device
 to enter EDL

On Mon, Apr 15, 2024 at 04:49:03PM +0800, Qiang Yu wrote:
> Add sysfs entry to allow users of MHI bus force device to enter EDL.
> Considering that the way to enter EDL mode varies from device to device and
> some devices even do not support EDL. Hence, add a callback edl_trigger in
> mhi controller as part of the sysfs entry to be invoked and MHI core will
> only create EDL sysfs entry for mhi controller that provides edl_trigger
> callback. All of the process a specific device required to enter EDL mode
> can be placed in this callback.
> 
> Signed-off-by: Qiang Yu <quic_qianyu@...cinc.com>
> ---
>  Documentation/ABI/stable/sysfs-bus-mhi | 11 +++++++++++
>  drivers/bus/mhi/host/init.c            | 35 ++++++++++++++++++++++++++++++++++
>  include/linux/mhi.h                    |  2 ++
>  3 files changed, 48 insertions(+)
> 
> diff --git a/Documentation/ABI/stable/sysfs-bus-mhi b/Documentation/ABI/stable/sysfs-bus-mhi
> index 1a47f9e..d0bf9ae 100644
> --- a/Documentation/ABI/stable/sysfs-bus-mhi
> +++ b/Documentation/ABI/stable/sysfs-bus-mhi
> @@ -29,3 +29,14 @@ Description:	Initiates a SoC reset on the MHI controller.  A SoC reset is
>                  This can be useful as a method of recovery if the device is
>                  non-responsive, or as a means of loading new firmware as a
>                  system administration task.
> +
> +What:           /sys/bus/mhi/devices/.../force_edl

s/force_edl/trigger_edl

> +Date:           April 2024
> +KernelVersion:  6.9
> +Contact:        mhi@...ts.linux.dev
> +Description:    Force devices to enter EDL (emergency download) mode. Only MHI

How can the user trigger EDL mode? Writing to this file? If so, what is the
value?

'Emergency Download'

> +                controller that supports EDL mode and provides a mechanism for
> +                manually triggering EDL contains this file. Once in EDL mode,

'This entry only exists for devices capable of entering the EDL mode using the
standard EDL triggering mechanism defined in the MHI spec <insert the version>.'

> +                the flash programmer image can be downloaded to the device to
> +                enter the flash programmer execution environment. This can be
> +                useful if user wants to update firmware.

It'd be good to mention the OS tool like QDL that is used to download firmware
over EDL.

> diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
> index 44f9349..333ac94 100644
> --- a/drivers/bus/mhi/host/init.c
> +++ b/drivers/bus/mhi/host/init.c
> @@ -127,6 +127,32 @@ static ssize_t soc_reset_store(struct device *dev,
>  }
>  static DEVICE_ATTR_WO(soc_reset);
>  
> +static ssize_t force_edl_store(struct device *dev,

s/force_edl/trigger_edl

> +			       struct device_attribute *attr,
> +			       const char *buf, size_t count)
> +{
> +	struct mhi_device *mhi_dev = to_mhi_device(dev);
> +	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
> +	unsigned long val;
> +	int ret;
> +
> +	ret = kstrtoul(buf, 10, &val);
> +	if (ret < 0) {
> +		dev_err(dev, "Could not parse string: %d\n", ret);

No need to print error.

> +		return ret;
> +	}
> +
> +	if (!val)
> +		return count;

What does this mean?

> +
> +	ret = mhi_cntrl->edl_trigger(mhi_cntrl);
> +	if (ret)
> +		return ret;
> +
> +	return count;
> +}
> +static DEVICE_ATTR_WO(force_edl);
> +
>  static struct attribute *mhi_dev_attrs[] = {
>  	&dev_attr_serial_number.attr,
>  	&dev_attr_oem_pk_hash.attr,
> @@ -1018,6 +1044,12 @@ int mhi_register_controller(struct mhi_controller *mhi_cntrl,
>  	if (ret)
>  		goto err_release_dev;
>  
> +	if (mhi_cntrl->edl_trigger) {
> +		ret = sysfs_create_file(&mhi_dev->dev.kobj, &dev_attr_force_edl.attr);
> +		if (ret)
> +			goto err_release_dev;
> +	}
> +
>  	mhi_cntrl->mhi_dev = mhi_dev;
>  
>  	mhi_create_debugfs(mhi_cntrl);
> @@ -1051,6 +1083,9 @@ void mhi_unregister_controller(struct mhi_controller *mhi_cntrl)
>  	mhi_deinit_free_irq(mhi_cntrl);
>  	mhi_destroy_debugfs(mhi_cntrl);
>  
> +	if (mhi_cntrl->edl_trigger)
> +		sysfs_remove_file(&mhi_dev->dev.kobj, &dev_attr_force_edl.attr);
> +
>  	destroy_workqueue(mhi_cntrl->hiprio_wq);
>  	kfree(mhi_cntrl->mhi_cmd);
>  	kfree(mhi_cntrl->mhi_event);
> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> index cde01e1..8280545 100644
> --- a/include/linux/mhi.h
> +++ b/include/linux/mhi.h
> @@ -353,6 +353,7 @@ struct mhi_controller_config {
>   * @read_reg: Read a MHI register via the physical link (required)
>   * @write_reg: Write a MHI register via the physical link (required)
>   * @reset: Controller specific reset function (optional)
> + * @edl_trigger: CB function to enter EDL mode (optional)

s/enter/trigger

- Mani

-- 
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