linux-kernel - Re: [PATCH v1] platform/chrome: cros_usbpd_notify: defer probe when parent EC driver isn't ready

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Message-ID: <aNcG_3_eBHX8Q0bl@google.com>
Date: Fri, 26 Sep 2025 21:34:55 +0000
From: Benson Leung <bleung@...gle.com>
To: Jameson Thies <jthies@...gle.com>
Cc: akuchynski@...omium.org, bleung@...omium.org,
	abhishekpandit@...omium.org, tzungbi@...nel.org,
	chrome-platform@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] platform/chrome: cros_usbpd_notify: defer probe when
 parent EC driver isn't ready

Hi Jameson,

On Fri, Sep 26, 2025 at 08:22:34PM +0000, Jameson Thies wrote:
> The cros-usbpd-notify-acpi probe currently does not exit when it fails
> to get a pointer to the ChromeOS EC device. It is expected behavior on
> older devices, where GOOG0004 is not a parent of GOOG0003.
> 
> Update the cros-usbpd-notify-acpi probe to check for a GOOG0004 parent
> fwnode. If the device has correct device hierarchy and fails to get an
> EC device pointer, defer the probe function.
> 
> Signed-off-by: Jameson Thies <jthies@...gle.com>

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


> ---
>  drivers/platform/chrome/cros_usbpd_notify.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/platform/chrome/cros_usbpd_notify.c b/drivers/platform/chrome/cros_usbpd_notify.c
> index 313d2bcd577b..2681bf9d0159 100644
> --- a/drivers/platform/chrome/cros_usbpd_notify.c
> +++ b/drivers/platform/chrome/cros_usbpd_notify.c
> @@ -6,6 +6,7 @@
>   */
>  
>  #include <linux/acpi.h>
> +#include <linux/fwnode.h>
>  #include <linux/mod_devicetable.h>
>  #include <linux/module.h>
>  #include <linux/platform_data/cros_ec_proto.h>
> @@ -15,6 +16,7 @@
>  #define DRV_NAME "cros-usbpd-notify"
>  #define DRV_NAME_PLAT_ACPI "cros-usbpd-notify-acpi"
>  #define ACPI_DRV_NAME "GOOG0003"
> +#define CREC_DRV_NAME "GOOG0004"
>  
>  static BLOCKING_NOTIFIER_HEAD(cros_usbpd_notifier_list);
>  
> @@ -98,8 +100,9 @@ static int cros_usbpd_notify_probe_acpi(struct platform_device *pdev)
>  {
>  	struct cros_usbpd_notify_data *pdnotify;
>  	struct device *dev = &pdev->dev;
> -	struct acpi_device *adev;
> +	struct acpi_device *adev, *parent_adev;
>  	struct cros_ec_device *ec_dev;
> +	struct fwnode_handle *parent_fwnode;
>  	acpi_status status;
>  
>  	adev = ACPI_COMPANION(dev);
> @@ -114,8 +117,18 @@ static int cros_usbpd_notify_probe_acpi(struct platform_device *pdev)
>  		/*
>  		 * We continue even for older devices which don't have the
>  		 * correct device heirarchy, namely, GOOG0003 is a child
> -		 * of GOOG0004.
> +		 * of GOOG0004. If GOOG0003 is a child of GOOG0004 and we
> +		 * can't get a pointer to the Chrome EC device, defer the
> +		 * probe function.
>  		 */
> +		parent_fwnode = fwnode_call_ptr_op(dev->fwnode, get_parent);
> +		if (parent_fwnode) {
> +			parent_adev = to_acpi_device_node(parent_fwnode);
> +			if (parent_adev &&
> +			    acpi_dev_hid_match(parent_adev, CREC_DRV_NAME)) {
> +				return -EPROBE_DEFER;
> +			}
> +		}
>  		dev_warn(dev, "Couldn't get Chrome EC device pointer.\n");
>  	}
>  
> 
> base-commit: 48633acccf38d706d7b368400647bb9db9caf1ae
> -- 
> 2.51.0.618.g983fd99d29-goog
> 

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