[PATCH v5 4/4] drm/xe/bmg: Update Wa_22019338487
Rodrigo Vivi
rodrigo.vivi at intel.com
Fri Jun 20 13:44:02 UTC 2025
On Wed, Jun 18, 2025 at 11:50:01AM -0700, Lucas De Marchi wrote:
> From: Vinay Belgaumkar <vinay.belgaumkar at intel.com>
>
> Limit GT max frequency to 2600MHz and wait for frequency to reduce
> before proceeding with a transient flush. This is really only needed for
> the transient flush: if L2 flush is needed due to 16023588340 then
> there's no need to do this additional wait since we are already using
> the bigger hammer.
>
> v2: Use generic names, ensure user set max frequency requests wait
> for flush to complete (Rodrigo)
> v3:
> - User requests wait via wait_var_event_timeout (Lucas)
> - Close races on flush + user requests (Lucas)
> - Fix xe_guc_pc_remove_flush_freq_limit() being called on last gt
> rather than root gt (Lucas)
> v4:
> - Only apply the freq reducing part if a TDF is needed: L2 flush trumps
> the need for waiting a lower frequency
>
> Fixes: aaa08078e725 ("drm/xe/bmg: Apply Wa_22019338487")
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com> # v3
> Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar at intel.com>
> Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
> ---
>
> Rodrigo, since the change in v4 changed it considerably, please let me
> know if your review still stands
It does. I'm glad we could reduce the scope and impact of this w/a here.
Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> ---
> drivers/gpu/drm/xe/xe_device.c | 8 ++-
> drivers/gpu/drm/xe/xe_guc_pc.c | 125 +++++++++++++++++++++++++++++++++++
> drivers/gpu/drm/xe/xe_guc_pc.h | 2 +
> drivers/gpu/drm/xe/xe_guc_pc_types.h | 2 +
> 4 files changed, 135 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
> index 8396612b68d4b..c3aee79aa1acb 100644
> --- a/drivers/gpu/drm/xe/xe_device.c
> +++ b/drivers/gpu/drm/xe/xe_device.c
> @@ -40,6 +40,7 @@
> #include "xe_gt_printk.h"
> #include "xe_gt_sriov_vf.h"
> #include "xe_guc.h"
> +#include "xe_guc_pc.h"
> #include "xe_hw_engine_group.h"
> #include "xe_hwmon.h"
> #include "xe_irq.h"
> @@ -1066,11 +1067,14 @@ void xe_device_td_flush(struct xe_device *xe)
> return;
>
> root_gt = xe_root_mmio_gt(xe);
> - if (XE_WA(root_gt, 16023588340))
> + if (XE_WA(root_gt, 16023588340)) {
> /* A transient flush is not sufficient: flush the L2 */
> xe_device_l2_flush(xe);
> - else
> + } else {
> + xe_guc_pc_apply_flush_freq_limit(&root_gt->uc.guc.pc);
> tdf_request_sync(xe);
> + xe_guc_pc_remove_flush_freq_limit(&root_gt->uc.guc.pc);
> + }
> }
>
> u32 xe_device_ccs_bytes(struct xe_device *xe, u64 size)
> diff --git a/drivers/gpu/drm/xe/xe_guc_pc.c b/drivers/gpu/drm/xe/xe_guc_pc.c
> index 538b4ea61c17c..eb3552baa6029 100644
> --- a/drivers/gpu/drm/xe/xe_guc_pc.c
> +++ b/drivers/gpu/drm/xe/xe_guc_pc.c
> @@ -7,7 +7,9 @@
>
> #include <linux/cleanup.h>
> #include <linux/delay.h>
> +#include <linux/jiffies.h>
> #include <linux/ktime.h>
> +#include <linux/wait_bit.h>
>
> #include <drm/drm_managed.h>
> #include <drm/drm_print.h>
> @@ -53,9 +55,11 @@
> #define LNL_MERT_FREQ_CAP 800
> #define BMG_MERT_FREQ_CAP 2133
> #define BMG_MIN_FREQ 1200
> +#define BMG_MERT_FLUSH_FREQ_CAP 2600
>
> #define SLPC_RESET_TIMEOUT_MS 5 /* roughly 5ms, but no need for precision */
> #define SLPC_RESET_EXTENDED_TIMEOUT_MS 1000 /* To be used only at pc_start */
> +#define SLPC_ACT_FREQ_TIMEOUT_MS 100
>
> /**
> * DOC: GuC Power Conservation (PC)
> @@ -143,6 +147,36 @@ static int wait_for_pc_state(struct xe_guc_pc *pc,
> return -ETIMEDOUT;
> }
>
> +static int wait_for_flush_complete(struct xe_guc_pc *pc)
> +{
> + const unsigned long timeout = msecs_to_jiffies(30);
> +
> + if (!wait_var_event_timeout(&pc->flush_freq_limit,
> + !atomic_read(&pc->flush_freq_limit),
> + timeout))
> + return -ETIMEDOUT;
> +
> + return 0;
> +}
> +
> +static int wait_for_act_freq_limit(struct xe_guc_pc *pc, u32 freq)
> +{
> + int timeout_us = SLPC_ACT_FREQ_TIMEOUT_MS * USEC_PER_MSEC;
> + int slept, wait = 10;
> +
> + for (slept = 0; slept < timeout_us;) {
> + if (xe_guc_pc_get_act_freq(pc) <= freq)
> + return 0;
> +
> + usleep_range(wait, wait << 1);
> + slept += wait;
> + wait <<= 1;
> + if (slept + wait > timeout_us)
> + wait = timeout_us - slept;
> + }
> +
> + return -ETIMEDOUT;
> +}
> static int pc_action_reset(struct xe_guc_pc *pc)
> {
> struct xe_guc_ct *ct = pc_to_ct(pc);
> @@ -689,6 +723,11 @@ static int xe_guc_pc_set_max_freq_locked(struct xe_guc_pc *pc, u32 freq)
> */
> int xe_guc_pc_set_max_freq(struct xe_guc_pc *pc, u32 freq)
> {
> + if (XE_WA(pc_to_gt(pc), 22019338487)) {
> + if (wait_for_flush_complete(pc) != 0)
> + return -EAGAIN;
> + }
> +
> guard(mutex)(&pc->freq_lock);
>
> return xe_guc_pc_set_max_freq_locked(pc, freq);
> @@ -889,6 +928,92 @@ static int pc_adjust_requested_freq(struct xe_guc_pc *pc)
> return ret;
> }
>
> +static bool needs_flush_freq_limit(struct xe_guc_pc *pc)
> +{
> + struct xe_gt *gt = pc_to_gt(pc);
> +
> + return XE_WA(gt, 22019338487) &&
> + pc->rp0_freq > BMG_MERT_FLUSH_FREQ_CAP;
> +}
> +
> +/**
> + * xe_guc_pc_apply_flush_freq_limit() - Limit max GT freq during L2 flush
> + * @pc: the xe_guc_pc object
> + *
> + * As per the WA, reduce max GT frequency during L2 cache flush
> + */
> +void xe_guc_pc_apply_flush_freq_limit(struct xe_guc_pc *pc)
> +{
> + struct xe_gt *gt = pc_to_gt(pc);
> + u32 max_freq;
> + int ret;
> +
> + if (!needs_flush_freq_limit(pc))
> + return;
> +
> + guard(mutex)(&pc->freq_lock);
> +
> + ret = xe_guc_pc_get_max_freq_locked(pc, &max_freq);
> + if (!ret && max_freq > BMG_MERT_FLUSH_FREQ_CAP) {
> + ret = pc_set_max_freq(pc, BMG_MERT_FLUSH_FREQ_CAP);
> + if (ret) {
> + xe_gt_err_once(gt, "Failed to cap max freq on flush to %u, %pe\n",
> + BMG_MERT_FLUSH_FREQ_CAP, ERR_PTR(ret));
> + return;
> + }
> +
> + atomic_set(&pc->flush_freq_limit, 1);
> +
> + /*
> + * If user has previously changed max freq, stash that value to
> + * restore later, otherwise use the current max. New user
> + * requests wait on flush.
> + */
> + if (pc->user_requested_max != 0)
> + pc->stashed_max_freq = pc->user_requested_max;
> + else
> + pc->stashed_max_freq = max_freq;
> + }
> +
> + /*
> + * Wait for actual freq to go below the flush cap: even if the previous
> + * max was below cap, the current one might still be above it
> + */
> + ret = wait_for_act_freq_limit(pc, BMG_MERT_FLUSH_FREQ_CAP);
> + if (ret)
> + xe_gt_err_once(gt, "Actual freq did not reduce to %u, %pe\n",
> + BMG_MERT_FLUSH_FREQ_CAP, ERR_PTR(ret));
> +}
> +
> +/**
> + * xe_guc_pc_remove_flush_freq_limit() - Remove max GT freq limit after L2 flush completes.
> + * @pc: the xe_guc_pc object
> + *
> + * Retrieve the previous GT max frequency value.
> + */
> +void xe_guc_pc_remove_flush_freq_limit(struct xe_guc_pc *pc)
> +{
> + struct xe_gt *gt = pc_to_gt(pc);
> + int ret = 0;
> +
> + if (!needs_flush_freq_limit(pc))
> + return;
> +
> + if (!atomic_read(&pc->flush_freq_limit))
> + return;
> +
> + mutex_lock(&pc->freq_lock);
> +
> + ret = pc_set_max_freq(>->uc.guc.pc, pc->stashed_max_freq);
> + if (ret)
> + xe_gt_err_once(gt, "Failed to restore max freq %u:%d",
> + pc->stashed_max_freq, ret);
> +
> + atomic_set(&pc->flush_freq_limit, 0);
> + mutex_unlock(&pc->freq_lock);
> + wake_up_var(&pc->flush_freq_limit);
> +}
> +
> static int pc_set_mert_freq_cap(struct xe_guc_pc *pc)
> {
> int ret;
> diff --git a/drivers/gpu/drm/xe/xe_guc_pc.h b/drivers/gpu/drm/xe/xe_guc_pc.h
> index 0a2664d5c8114..52ecdd5ddbff2 100644
> --- a/drivers/gpu/drm/xe/xe_guc_pc.h
> +++ b/drivers/gpu/drm/xe/xe_guc_pc.h
> @@ -38,5 +38,7 @@ u64 xe_guc_pc_mc6_residency(struct xe_guc_pc *pc);
> void xe_guc_pc_init_early(struct xe_guc_pc *pc);
> int xe_guc_pc_restore_stashed_freq(struct xe_guc_pc *pc);
> void xe_guc_pc_raise_unslice(struct xe_guc_pc *pc);
> +void xe_guc_pc_apply_flush_freq_limit(struct xe_guc_pc *pc);
> +void xe_guc_pc_remove_flush_freq_limit(struct xe_guc_pc *pc);
>
> #endif /* _XE_GUC_PC_H_ */
> diff --git a/drivers/gpu/drm/xe/xe_guc_pc_types.h b/drivers/gpu/drm/xe/xe_guc_pc_types.h
> index 2978ac9a249b5..c02053948a579 100644
> --- a/drivers/gpu/drm/xe/xe_guc_pc_types.h
> +++ b/drivers/gpu/drm/xe/xe_guc_pc_types.h
> @@ -15,6 +15,8 @@
> struct xe_guc_pc {
> /** @bo: GGTT buffer object that is shared with GuC PC */
> struct xe_bo *bo;
> + /** @flush_freq_limit: 1 when max freq changes are limited by driver */
> + atomic_t flush_freq_limit;
> /** @rp0_freq: HW RP0 frequency - The Maximum one */
> u32 rp0_freq;
> /** @rpa_freq: HW RPa frequency - The Achievable one */
>
> --
> 2.49.0
>
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