[PATCH 2/2] drm/xe/guc: Add support for NPK as a GuC log target

[Cavitt, Jonathan]

-----Original Message-----
From: Intel-xe <intel-xe-bounces at lists.freedesktop.org> On Behalf Of John.C.Harrison at Intel.com
Sent: Wednesday, June 11, 2025 2:06 PM
To: Intel-Xe at Lists.FreeDesktop.Org
Cc: Harrison, John C <john.c.harrison at intel.com>
Subject: [PATCH 2/2] drm/xe/guc: Add support for NPK as a GuC log target
> 
> From: John Harrison <John.C.Harrison at Intel.com>
> 
> The GuC has an option to write log data via NPK. This is basically a
> magic IO address that GuC writes arbitrary data to and which can be
> logged by a suitable hardware logger. This can allow retrieval of the
> GuC log in hardware debug environments even when the system as a whole
> dies horribly.
> 
> Signed-off-by: John Harrison <John.C.Harrison at Intel.com>

So, this is basically a new modparam value that redirects GuC logs to
a specific IO address?  I take it guc_log_target = 2 is the default value, and
guc_log_target = 1 would print the logs to stdout, then?  I'd ask why we
use 0 as a default value and not just default to 2 all the time, but I think I
already know why (we need to guard against guc_log_target = 0 anyways
to prevent printing to stdin).

I also take it this is modified on boot by, for example, writing
"xe.guc_log_target=1" to CMDLINE_LINUX_DEFAULT as a part of the grub file.

Yeah, seems good.
Reviewed-by: Jonathan Cavitt <jonathan.cavitt at intel.com>
-Jonathan Cavitt

> ---
>  drivers/gpu/drm/xe/xe_guc.c    | 4 ++++
>  drivers/gpu/drm/xe/xe_module.c | 4 ++++
>  drivers/gpu/drm/xe/xe_module.h | 1 +
>  3 files changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc.c b/drivers/gpu/drm/xe/xe_guc.c
> index e16d19b44bcc..9c0e3113f7d5 100644
> --- a/drivers/gpu/drm/xe/xe_guc.c
> +++ b/drivers/gpu/drm/xe/xe_guc.c
> @@ -35,6 +35,7 @@
>  #include "xe_guc_submit.h"
>  #include "xe_memirq.h"
>  #include "xe_mmio.h"
> +#include "xe_module.h"
>  #include "xe_platform_types.h"
>  #include "xe_sriov.h"
>  #include "xe_uc.h"
> @@ -74,6 +75,9 @@ static u32 guc_ctl_debug_flags(struct xe_guc *guc)
>  	else
>  		flags |= FIELD_PREP(GUC_LOG_VERBOSITY, GUC_LOG_LEVEL_TO_VERBOSITY(level));
>  
> +	if (xe_modparam.guc_log_target)
> +		flags |= FIELD_PREP(GUC_LOG_DESTINATION, xe_modparam.guc_log_target);
> +
>  	return flags;
>  }
>  
> diff --git a/drivers/gpu/drm/xe/xe_module.c b/drivers/gpu/drm/xe/xe_module.c
> index 1c4dfafbcd0b..fc8c681819b9 100644
> --- a/drivers/gpu/drm/xe/xe_module.c
> +++ b/drivers/gpu/drm/xe/xe_module.c
> @@ -21,6 +21,7 @@
>  struct xe_modparam xe_modparam = {
>  	.probe_display = true,
>  	.guc_log_level = 3,
> +	.guc_log_target = 0,
>  	.force_probe = CONFIG_DRM_XE_FORCE_PROBE,
>  #ifdef CONFIG_PCI_IOV
>  	.max_vfs = IS_ENABLED(CONFIG_DRM_XE_DEBUG) ? ~0 : 0,
> @@ -45,6 +46,9 @@ MODULE_PARM_DESC(vram_bar_size, "Set the vram bar size (in MiB) - <0=disable-res
>  module_param_named(guc_log_level, xe_modparam.guc_log_level, int, 0600);
>  MODULE_PARM_DESC(guc_log_level, "GuC firmware logging level (0=disable, 1..5=enable with verbosity min..max)");
>  
> +module_param_named(guc_log_target, xe_modparam.guc_log_target, int, 0600);
> +MODULE_PARM_DESC(guc_log_target, "GuC firmware logging target (0=memory [default], 1 = NPK, 2 = memory + NPK)");
> +
>  module_param_named_unsafe(guc_firmware_path, xe_modparam.guc_firmware_path, charp, 0400);
>  MODULE_PARM_DESC(guc_firmware_path,
>  		 "GuC firmware path to use instead of the default one");
> diff --git a/drivers/gpu/drm/xe/xe_module.h b/drivers/gpu/drm/xe/xe_module.h
> index 5a3bfea8b7b4..4d978f6f26b6 100644
> --- a/drivers/gpu/drm/xe/xe_module.h
> +++ b/drivers/gpu/drm/xe/xe_module.h
> @@ -14,6 +14,7 @@ struct xe_modparam {
>  	bool probe_display;
>  	u32 force_vram_bar_size;
>  	int guc_log_level;
> +	int guc_log_target;
>  	char *guc_firmware_path;
>  	char *huc_firmware_path;
>  	char *gsc_firmware_path;
> -- 
> 2.49.0
> 
>