Re: [PATCH v3] drm/xe/pcode: Allow checking for mailbox command support during driver probe

["Nilawar, Badal" <badal.nilawar@intel.com>]

On 13-11-2025 10:14, Raag Jadav wrote:
> If the device is running older pcode firmware, it is possible that newer
> mailbox commands are not supported by it. The respective functionality
> isn't useful in that case but nor is error logging, since it doesn't
> particularly signify anything wrong with pcode firmware or device as a
> whole. Log such failures as debug messages during driver probe which allows
> the caller to check for mailbox command support without it being reported
> as an error. This is useful in cases where we want to make a decision on
> driver functionality based on pcode return codes and a relatively simpler
> design choice compared to other solutions like checking pcode firmware
> version, which comes with additional complexity of binding every single
> command to a specific version and deems pcode commands useless in case the
> driver fails to obtain it for reasons unrelated to pcode.
>
> This only silences command related failures and still reports other
> failures as errors, so we don't end up hiding the genuine ones.
>
> v2: Split unsupported command cases
> v3: Add device bound check
>
> Signed-off-by: Raag Jadav <raag.jadav@intel.com>
> ---
>
> I've not followed the documented device_lock() rule here because
>
> 1. It'll deadlock in ->probe() path.
> 2. I don't know the code well enough to tell if it's really needed for
>     our case.
>
> So feel free to weigh in.
>
>   drivers/gpu/drm/xe/xe_device.h | 7 +++++++
>   drivers/gpu/drm/xe/xe_pcode.c  | 8 ++++++--
>   2 files changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_device.h b/drivers/gpu/drm/xe/xe_device.h
> index 32cc6323b7f6..e8f997546ae1 100644
> --- a/drivers/gpu/drm/xe/xe_device.h
> +++ b/drivers/gpu/drm/xe/xe_device.h
> @@ -12,6 +12,13 @@
>   #include "xe_gt_types.h"
>   #include "xe_sriov.h"
>   
> +static inline bool xe_is_bound(struct xe_device *xe)
> +{
> +	struct device *dev = xe->drm.dev;
> +
> +	return device_is_bound(dev);
> +}
> +
>   static inline struct xe_device *to_xe_device(const struct drm_device *dev)
>   {
>   	return container_of(dev, struct xe_device, drm);
> diff --git a/drivers/gpu/drm/xe/xe_pcode.c b/drivers/gpu/drm/xe/xe_pcode.c
> index 0d33c14ea0cf..0f1edf5155c4 100644
> --- a/drivers/gpu/drm/xe/xe_pcode.c
> +++ b/drivers/gpu/drm/xe/xe_pcode.c
> @@ -57,8 +57,12 @@ static int pcode_mailbox_status(struct xe_tile *tile)
>   	}
>   
>   	if (err) {
> -		drm_err(&tile_to_xe(tile)->drm, "PCODE Mailbox failed: %d %s",
> -			err_decode, err_str);
> +		if (err_decode == -ENXIO && !xe_is_bound(tile_to_xe(tile)))

Use -EBUSY here. The check should be against -6, which indicates "mailbox temporarily unsupported.

Thanks,
Badal

> +			drm_dbg(&tile_to_xe(tile)->drm, "PCODE Mailbox unsupported: %d %s",
> +				err_decode, err_str);
> +		else
> +			drm_err(&tile_to_xe(tile)->drm, "PCODE Mailbox failed: %d %s",
> +				err_decode, err_str);
>   
>   		return err_decode;
>   	}