linux-kernel - Re: [PATCH v9 6/7] mfd: cros_ec: differentiate SCP from EC by feature bit.

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Date:   Tue, 4 Jun 2019 10:55:54 -0700
From:   Benson Leung <bleung@...gle.com>
To:     Pi-Hsun Shih <pihsun@...omium.org>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Benson Leung <bleung@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Guenter Roeck <groeck@...omium.org>,
        open list <linux-kernel@...r.kernel.org>, bleung@...gle.com
Subject: Re: [PATCH v9 6/7] mfd: cros_ec: differentiate SCP from EC by
 feature bit.

On Fri, May 31, 2019 at 03:38:47PM +0800, Pi-Hsun Shih wrote:
> System Companion Processor (SCP) is Cortex M4 co-processor on some
> MediaTek platform that can run EC-style firmware. Since a SCP and EC
> would both exist on a system, and use the cros_ec_dev driver, we need to
> differentiate between them for the userspace, or they would both be
> registered at /dev/cros_ec, causing a conflict.
> 
> Signed-off-by: Pi-Hsun Shih <pihsun@...omium.org>

Reviewed-by: Benson Leung <bleung@...omium.org>

> 
> ---
> Changes from v8:
>  - No change.
> 
> Changes from v7:
>  - Address comments in v7.
>  - Rebase the series onto https://lore.kernel.org/patchwork/patch/1059196/.
> 
> Changes from v6, v5, v4, v3, v2:
>  - No change.
> 
> Changes from v1:
>  - New patch extracted from Patch 5.
> ---
>  drivers/mfd/cros_ec_dev.c            | 10 ++++++++++
>  include/linux/mfd/cros_ec.h          |  1 +
>  include/linux/mfd/cros_ec_commands.h |  2 +-
>  3 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
> index a5391f96eafd..66107de3dbce 100644
> --- a/drivers/mfd/cros_ec_dev.c
> +++ b/drivers/mfd/cros_ec_dev.c
> @@ -440,6 +440,16 @@ static int ec_device_probe(struct platform_device *pdev)
>  		ec_platform->ec_name = CROS_EC_DEV_TP_NAME;
>  	}
>  
> +	/* Check whether this is actually a SCP rather than an EC. */
> +	if (cros_ec_check_features(ec, EC_FEATURE_SCP)) {
> +		dev_info(dev, "CrOS SCP MCU detected.\n");
> +		/*
> +		 * Help userspace differentiating ECs from SCP,
> +		 * regardless of the probing order.
> +		 */
> +		ec_platform->ec_name = CROS_EC_DEV_SCP_NAME;
> +	}
> +
>  	/*
>  	 * Add the class device
>  	 * Link to the character device for creating the /dev entry
> diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
> index cfa78bb4990f..751cb3756d49 100644
> --- a/include/linux/mfd/cros_ec.h
> +++ b/include/linux/mfd/cros_ec.h
> @@ -27,6 +27,7 @@
>  #define CROS_EC_DEV_PD_NAME "cros_pd"
>  #define CROS_EC_DEV_TP_NAME "cros_tp"
>  #define CROS_EC_DEV_ISH_NAME "cros_ish"
> +#define CROS_EC_DEV_SCP_NAME "cros_scp"
>  
>  /*
>   * The EC is unresponsive for a time after a reboot command.  Add a
> diff --git a/include/linux/mfd/cros_ec_commands.h b/include/linux/mfd/cros_ec_commands.h
> index dcec96f01879..8b578b4c1ec7 100644
> --- a/include/linux/mfd/cros_ec_commands.h
> +++ b/include/linux/mfd/cros_ec_commands.h
> @@ -884,7 +884,7 @@ enum ec_feature_code {
>  	EC_FEATURE_REFINED_TABLET_MODE_HYSTERESIS = 37,
>  	/* EC supports audio codec. */
>  	EC_FEATURE_AUDIO_CODEC = 38,
> -	/* EC Supports SCP. */
> +	/* The MCU is a System Companion Processor (SCP). */
>  	EC_FEATURE_SCP = 39,
>  	/* The MCU is an Integrated Sensor Hub */
>  	EC_FEATURE_ISH = 40,
> -- 
> 2.22.0.rc1.257.g3120a18244-goog
> 

-- 
Benson Leung
Staff Software Engineer
Chrome OS Kernel
Google Inc.
bleung@...gle.com
Chromium OS Project
bleung@...omium.org

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