From: Matt Roper Date: Wed, 18 Feb 2026 22:09:13 +0000 (-0800) Subject: drm/xe/reg_sr: Add debugfs to verify status of reg_sr programming X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=d389489225b85aac3ad90ed8b5661679f27a2da4;p=thirdparty%2Fkernel%2Flinux.git 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read back the registers referenced on a GT's save-restore lists and print any cases where the desired programming is no longer in effect.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: Ashutosh Dixit Link: https://patch.msgid.link/20260218-sr_verify-v4-2-35d6deeb3421@intel.com Signed-off-by: Matt Roper --- diff --git a/drivers/gpu/drm/xe/xe_gt_debugfs.c b/drivers/gpu/drm/xe/xe_gt_debugfs.c index 4363bc9c36067..aa43427a9f4b8 100644 --- a/drivers/gpu/drm/xe/xe_gt_debugfs.c +++ b/drivers/gpu/drm/xe/xe_gt_debugfs.c @@ -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(>->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 */ diff --git a/drivers/gpu/drm/xe/xe_reg_sr.c b/drivers/gpu/drm/xe/xe_reg_sr.c index 1ac911fc6e943..75aa4426b3ec6 100644 --- a/drivers/gpu/drm/xe/xe_reg_sr.c +++ b/drivers/gpu/drm/xe/xe_reg_sr.c @@ -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(>->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); + } +} diff --git a/drivers/gpu/drm/xe/xe_reg_sr.h b/drivers/gpu/drm/xe/xe_reg_sr.h index 51fbba423e27f..cd133a09aa9b3 100644 --- a/drivers/gpu/drm/xe/xe_reg_sr.h +++ b/drivers/gpu/drm/xe/xe_reg_sr.h @@ -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);