Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx> writes:
> There is a possibility on gen9 hardware to miss the forcewake ack
> message. The recommended workaround is to use another free
> bit and toggle it until original bit is successfully acknowledged.
>
> Some future gen9 revs might or might not fix the underlying issue but
> the fallback to reserve bit dance can be considered as harmless:
> without the ack timeout we never reach the reserve bit forcewake.
> Thus as of now we adopt a blanket approach for all gen9 and leave
> the bypassing the reserve bit approach for future patches if
> corresponding hw revisions do appear.
>
> Commit 83e3337204b2 ("drm/i915: Increase maximum polling time to 50ms
> for forcewake request/clear ack") did increase the forcewake timeout.
> If the issue was a delayed ack, future work could include finding
> a suitable timeout value both for primary ack and reserve toggle
> to reduce the worst case latency.
>
> v2: use bit 15, naming, comment (Chris), only wait fallback ack
>
And then I forgot to change the naming in the subject and
commit message. Sigh
-Mika
> References: HSDES #1604254524
> References: https://bugs.freedesktop.org/show_bug.cgi?id=102051
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> Cc: Sagar Arun Kamble <sagar.a.kamble@xxxxxxxxx>
> Signed-off-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_reg.h | 5 +-
> drivers/gpu/drm/i915/intel_uncore.c | 141 +++++++++++++++++++++++++++++++++---
> 2 files changed, 134 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 8c775e96b4e4..f0f8f6059652 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -7774,8 +7774,9 @@ enum {
> #define FORCEWAKE_ACK_MEDIA_GEN9 _MMIO(0x0D88)
> #define FORCEWAKE_ACK_RENDER_GEN9 _MMIO(0x0D84)
> #define FORCEWAKE_ACK_BLITTER_GEN9 _MMIO(0x130044)
> -#define FORCEWAKE_KERNEL 0x1
> -#define FORCEWAKE_USER 0x2
> +#define FORCEWAKE_KERNEL BIT(0)
> +#define FORCEWAKE_USER BIT(1)
> +#define FORCEWAKE_KERNEL_FALLBACK BIT(15)
> #define FORCEWAKE_MT_ACK _MMIO(0x130040)
> #define ECOBUS _MMIO(0xa180)
> #define FORCEWAKE_MT_ENABLE (1<<5)
> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> index 96ee6b2754be..588ae35c8c9a 100644
> --- a/drivers/gpu/drm/i915/intel_uncore.c
> +++ b/drivers/gpu/drm/i915/intel_uncore.c
> @@ -69,17 +69,108 @@ fw_domain_arm_timer(struct intel_uncore_forcewake_domain *d)
> HRTIMER_MODE_REL);
> }
>
> +static inline int
> +__wait_for_ack(const struct drm_i915_private *i915,
> + const struct intel_uncore_forcewake_domain *d,
> + const u32 ack,
> + const u32 value)
> +{
> + return wait_for_atomic((__raw_i915_read32(i915, d->reg_ack) & ack) == value,
> + FORCEWAKE_ACK_TIMEOUT_MS);
> +}
> +
> +
> +static inline int
> +wait_ack_clear(const struct drm_i915_private *i915,
> + const struct intel_uncore_forcewake_domain *d,
> + const u32 ack)
> +{
> + return __wait_for_ack(i915, d, ack, 0);
> +}
> +
> +static inline int
> +wait_ack_set(const struct drm_i915_private *i915,
> + const struct intel_uncore_forcewake_domain *d,
> + const u32 ack)
> +{
> + return __wait_for_ack(i915, d, ack, ack);
> +}
> +
> static inline void
> fw_domain_wait_ack_clear(const struct drm_i915_private *i915,
> const struct intel_uncore_forcewake_domain *d)
> {
> - if (wait_for_atomic((__raw_i915_read32(i915, d->reg_ack) &
> - FORCEWAKE_KERNEL) == 0,
> - FORCEWAKE_ACK_TIMEOUT_MS))
> + if (wait_ack_clear(i915, d, FORCEWAKE_KERNEL))
> DRM_ERROR("%s: timed out waiting for forcewake ack to clear.\n",
> intel_uncore_forcewake_domain_to_str(d->id));
> }
>
> +static int
> +wait_ack_with_fallback(const struct drm_i915_private *i915,
> + const struct intel_uncore_forcewake_domain *d,
> + const u32 ack,
> + const u32 value)
> +{
> + int ret;
> +
> + /*
> + * There is a possibility of driver's wake request colliding
> + * with hardware's own wake requests and that can cause
> + * hardware to not deliver the driver's ack message.
> + *
> + * Use a fallback bit toggle to kick the gpu state machine
> + * in hopes that the original ack will be delivered along with
> + * the fallback ack.
> + *
> + * This workaround is described in HSDES #1604254524
> + */
> +
> + wait_ack_clear(i915, d, FORCEWAKE_KERNEL_FALLBACK);
> + __raw_i915_write32(i915, d->reg_set,
> + _MASKED_BIT_ENABLE(FORCEWAKE_KERNEL_FALLBACK));
> + wait_ack_set(i915, d, FORCEWAKE_KERNEL_FALLBACK);
> +
> + ret = (__raw_i915_read32(i915, d->reg_ack) & ack) == value;
> +
> + __raw_i915_write32(i915, d->reg_set,
> + _MASKED_BIT_DISABLE(FORCEWAKE_KERNEL_FALLBACK));
> +
> + return ret;
> +}
> +
> +enum ack_type {
> + ACK_CLEAR = 0,
> + ACK_SET
> +};
> +
> +static int
> +fw_domain_wait_ack_with_fallback(const struct drm_i915_private *i915,
> + const struct intel_uncore_forcewake_domain *d,
> + const enum ack_type type)
> +{
> + int retry = 10;
> + int ret;
> +
> + do {
> + ret = wait_ack_with_fallback(i915, d, FORCEWAKE_KERNEL,
> + type == ACK_SET ?
> + FORCEWAKE_KERNEL : 0);
> + } while (ret && --retry);
> +
> + return ret;
> +}
> +
> +static inline void
> +fw_domain_wait_ack_clear_fallback(const struct drm_i915_private *i915,
> + const struct intel_uncore_forcewake_domain *d)
> +{
> + if (likely(!wait_ack_clear(i915, d, FORCEWAKE_KERNEL)))
> + return;
> +
> + if (fw_domain_wait_ack_with_fallback(i915, d, ACK_CLEAR))
> + fw_domain_wait_ack_clear(i915, d);
> +}
> +
> static inline void
> fw_domain_get(struct drm_i915_private *i915,
> const struct intel_uncore_forcewake_domain *d)
> @@ -88,17 +179,26 @@ fw_domain_get(struct drm_i915_private *i915,
> }
>
> static inline void
> -fw_domain_wait_ack(const struct drm_i915_private *i915,
> - const struct intel_uncore_forcewake_domain *d)
> +fw_domain_wait_ack_set(const struct drm_i915_private *i915,
> + const struct intel_uncore_forcewake_domain *d)
> {
> - if (wait_for_atomic((__raw_i915_read32(i915, d->reg_ack) &
> - FORCEWAKE_KERNEL),
> - FORCEWAKE_ACK_TIMEOUT_MS))
> + if (wait_ack_set(i915, d, FORCEWAKE_KERNEL))
> DRM_ERROR("%s: timed out waiting for forcewake ack request.\n",
> intel_uncore_forcewake_domain_to_str(d->id));
> }
>
> static inline void
> +fw_domain_wait_ack_set_fallback(const struct drm_i915_private *i915,
> + const struct intel_uncore_forcewake_domain *d)
> +{
> + if (likely(!wait_ack_set(i915, d, FORCEWAKE_KERNEL)))
> + return;
> +
> + if (fw_domain_wait_ack_with_fallback(i915, d, ACK_SET))
> + fw_domain_wait_ack_set(i915, d);
> +}
> +
> +static inline void
> fw_domain_put(const struct drm_i915_private *i915,
> const struct intel_uncore_forcewake_domain *d)
> {
> @@ -119,7 +219,27 @@ fw_domains_get(struct drm_i915_private *i915, enum forcewake_domains fw_domains)
> }
>
> for_each_fw_domain_masked(d, fw_domains, i915, tmp)
> - fw_domain_wait_ack(i915, d);
> + fw_domain_wait_ack_set(i915, d);
> +
> + i915->uncore.fw_domains_active |= fw_domains;
> +}
> +
> +static void
> +fw_domains_get_with_fallback(struct drm_i915_private *i915,
> + enum forcewake_domains fw_domains)
> +{
> + struct intel_uncore_forcewake_domain *d;
> + unsigned int tmp;
> +
> + GEM_BUG_ON(fw_domains & ~i915->uncore.fw_domains);
> +
> + for_each_fw_domain_masked(d, fw_domains, i915, tmp) {
> + fw_domain_wait_ack_clear_fallback(i915, d);
> + fw_domain_get(i915, d);
> + }
> +
> + for_each_fw_domain_masked(d, fw_domains, i915, tmp)
> + fw_domain_wait_ack_set_fallback(i915, d);
>
> i915->uncore.fw_domains_active |= fw_domains;
> }
> @@ -1142,7 +1262,8 @@ static void intel_uncore_fw_domains_init(struct drm_i915_private *dev_priv)
> }
>
> if (INTEL_GEN(dev_priv) >= 9) {
> - dev_priv->uncore.funcs.force_wake_get = fw_domains_get;
> + dev_priv->uncore.funcs.force_wake_get =
> + fw_domains_get_with_fallback;
> dev_priv->uncore.funcs.force_wake_put = fw_domains_put;
> fw_domain_init(dev_priv, FW_DOMAIN_ID_RENDER,
> FORCEWAKE_RENDER_GEN9,
> --
> 2.11.0
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