Commit d3894892 authored by Matt Roper's avatar Matt Roper
Browse files

drm/xe/reg_sr: Add debugfs to verify status of reg_sr programming 



When applying save-restore register programming for workarounds, tuning
settings, and general device configuration we assume the programming was
successful.  However there are a number of cases where the desired
reg_sr programming can become lost:

 - workarounds implemented on the wrong RTP table might not get
   saved/restored at the right time leading to, for example, failure to
   re-apply the programming after engine resets
 - some hardware registers become "locked" and can no longer be updated
   after firmware or the driver finishes initializing them
 - sometimes the hardware teams just made a mistake when documenting the
   register and/or bits that needed to be programmed

Add a debugfs entry that will read back the registers referenced on a
GT's save-restore lists and print any cases where the desired
programming is no longer in effect.  Such cases might indicate the
presence of a driver/firmware bug, might indicate that the documentation
we were following has a mistake, or might be benign (occasionally
registers have broken read-back capability preventing verification, but
previous writes were still successful and effective).

For now we only verify the GT and engine reg_sr lists.  Verifying the
LRC list will require checking the expected programming against the
default_lrc contents, not the live registers (which may not reflect the
reg_sr programming if no context is actively running).

Reviewed-by: default avatarAshutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patch.msgid.link/20260218-sr_verify-v4-2-35d6deeb3421@intel.com


Signed-off-by: default avatarMatt Roper <matthew.d.roper@intel.com>
parent a41ee215

drivers/gpu/drm/xe/xe_gt_debugfs.c

+26 −0
Original line number Diff line number Diff line
@@ -155,6 +155,30 @@ static int register_save_restore(struct xe_gt *gt, struct drm_printer *p) 
	return 0;

}



/*

 * Check the registers referenced on a save-restore list and report any

 * save-restore entries that did not get applied.

 */

static int register_save_restore_check(struct xe_gt *gt, struct drm_printer *p)

{

	struct xe_hw_engine *hwe;

	enum xe_hw_engine_id id;



	CLASS(xe_force_wake, fw_ref)(gt_to_fw(gt), XE_FORCEWAKE_ALL);

	if (!xe_force_wake_ref_has_domain(fw_ref.domains, XE_FORCEWAKE_ALL)) {

		drm_printf(p, "ERROR: Could not acquire forcewake\n");

		return -ETIMEDOUT;

	}



	xe_reg_sr_readback_check(&gt->reg_sr, gt, p);

	for_each_hw_engine(hwe, gt, id)

		xe_reg_sr_readback_check(&hwe->reg_sr, gt, p);



	/* TODO: Check hwe->reg_lrc against contents of default_lrc. */



	return 0;

}



static int rcs_default_lrc(struct xe_gt *gt, struct drm_printer *p)

{

	xe_lrc_dump_default(p, gt, XE_ENGINE_CLASS_RENDER);
@@ -209,6 +233,8 @@ static const struct drm_info_list vf_safe_debugfs_list[] = { 
	{ "default_lrc_vecs", .show = xe_gt_debugfs_show_with_rpm, .data = vecs_default_lrc },

	{ "hwconfig", .show = xe_gt_debugfs_show_with_rpm, .data = hwconfig },

	{ "pat_sw_config", .show = xe_gt_debugfs_simple_show, .data = xe_pat_dump_sw_config },

	{ "register-save-restore-check",

		.show = xe_gt_debugfs_show_with_rpm, .data = register_save_restore_check },

};



/* everything else should be added here */

drivers/gpu/drm/xe/xe_reg_sr.c

+34 −0
Original line number Diff line number Diff line
@@ -208,3 +208,37 @@ void xe_reg_sr_dump(struct xe_reg_sr *sr, struct drm_printer *p) 
			   str_yes_no(entry->reg.masked),

			   str_yes_no(entry->reg.mcr));

}



static u32 readback_reg(struct xe_gt *gt, struct xe_reg reg)

{

	struct xe_reg_mcr mcr_reg = to_xe_reg_mcr(reg);



	if (reg.mcr)

		return xe_gt_mcr_unicast_read_any(gt, mcr_reg);

	else

		return xe_mmio_read32(&gt->mmio, reg);

}



/**

 * xe_reg_sr_readback_check() - Readback registers referenced in save/restore

 *     entries and check whether the programming is in place.

 * @sr: Save/restore entries

 * @gt: GT to read register from

 * @p: DRM printer to report discrepancies on

 */

void xe_reg_sr_readback_check(struct xe_reg_sr *sr,

			      struct xe_gt *gt,

			      struct drm_printer *p)

{

	struct xe_reg_sr_entry *entry;

	unsigned long offset;



	xa_for_each(&sr->xa, offset, entry) {

		u32 val = readback_reg(gt, entry->reg);

		u32 mask = entry->clr_bits | entry->set_bits;



		if ((val & mask) != entry->set_bits)

			drm_printf(p, "%#8lx & %#10x :: expected %#10x got %#10x\n",

				   offset, mask, entry->set_bits, val & mask);

	}

}

drivers/gpu/drm/xe/xe_reg_sr.h

+3 −0
Original line number Diff line number Diff line
@@ -19,6 +19,9 @@ struct drm_printer; 


int xe_reg_sr_init(struct xe_reg_sr *sr, const char *name, struct xe_device *xe);

void xe_reg_sr_dump(struct xe_reg_sr *sr, struct drm_printer *p);

void xe_reg_sr_readback_check(struct xe_reg_sr *sr,

			      struct xe_gt *gt,

			      struct drm_printer *p);



int xe_reg_sr_add(struct xe_reg_sr *sr, const struct xe_reg_sr_entry *e,

		  struct xe_gt *gt);