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

[Lucas De Marchi]

On Wed, Jun 11, 2025 at 04:51:24PM -0700, John Harrison wrote:
>On 6/11/2025 2:49 PM, Lucas De Marchi wrote:
>>On Wed, Jun 11, 2025 at 02:05:53PM -0700, John.C.Harrison at Intel.com 
>>wrote:
>>>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>
>>>---
>>>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);
>>
>>is this supported across the board for all platforms and firmware
>>versions? Otherwise, what'd happen if you have and old igfx and you are
>>debugging a new dgfx? or vice-versa.
>All platforms that have a GuC and all firmware builds that have been 
>supported under Linux. North PeaK is part of the host chipset not the 
>GuC or GT.

so I imagine this only works in igfx? I'm mostly concerned about this
being a module param and then you try to debug one card and get the
other to do what you don't want (or crash, or refuse to load). For
similar reason we've been adding these debug aids via configfs rather
than module param.  If it's harmless, then.... well guc_log_level is
already there, doesn't hurt much to have the other.

Lucas De Marchi