Re: [Intel-gfx] [PATCH 01/14] drm/i915/guc: Do not use 0 for GuC doorbell cookie
On 10/20/2017 12:06 AM, Michał Winiarski wrote: Apparently, this value is reserved and may be interpreted as changing doorbell ownership. Even though we're not observing any side effects now, let's skip over it to be consistent with the spec. Suggested-by: Sagar Arun Kamble Signed-off-by: Michał Winiarski Cc: Chris Wilson Cc: Sagar Arun Kamble --- drivers/gpu/drm/i915/i915_guc_submission.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c index a2e8114b739d..02ca2a412c62 100644 --- a/drivers/gpu/drm/i915/i915_guc_submission.c +++ b/drivers/gpu/drm/i915/i915_guc_submission.c @@ -475,9 +475,10 @@ static void guc_ring_doorbell(struct i915_guc_client *client) /* pointer of current doorbell cacheline */ db = __get_doorbell(client); - /* we're not expecting the doorbell cookie to change behind our back */ + /* we're not expecting the doorbell cookie to change behind our back, +* we also need to treat 0 as a reserved value */ Need to fix /* & */. Change looks good to me. Reviewed-by: Sagar Arun Kamble cookie = READ_ONCE(db->cookie); - WARN_ON_ONCE(xchg(&db->cookie, cookie + 1) != cookie); + WARN_ON_ONCE(xchg(&db->cookie, cookie + 1 ?: cookie + 2) != cookie); /* XXX: doorbell was lost and need to acquire it again */ GEM_BUG_ON(db->db_status != GUC_DOORBELL_ENABLED); ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
[Intel-gfx] [PATCH 01/14] drm/i915/guc: Do not use 0 for GuC doorbell cookie
Apparently, this value is reserved and may be interpreted as changing doorbell ownership. Even though we're not observing any side effects now, let's skip over it to be consistent with the spec. Suggested-by: Sagar Arun Kamble Signed-off-by: Michał Winiarski Cc: Chris Wilson Cc: Sagar Arun Kamble --- drivers/gpu/drm/i915/i915_guc_submission.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c index a2e8114b739d..02ca2a412c62 100644 --- a/drivers/gpu/drm/i915/i915_guc_submission.c +++ b/drivers/gpu/drm/i915/i915_guc_submission.c @@ -475,9 +475,10 @@ static void guc_ring_doorbell(struct i915_guc_client *client) /* pointer of current doorbell cacheline */ db = __get_doorbell(client); - /* we're not expecting the doorbell cookie to change behind our back */ + /* we're not expecting the doorbell cookie to change behind our back, +* we also need to treat 0 as a reserved value */ cookie = READ_ONCE(db->cookie); - WARN_ON_ONCE(xchg(&db->cookie, cookie + 1) != cookie); + WARN_ON_ONCE(xchg(&db->cookie, cookie + 1 ?: cookie + 2) != cookie); /* XXX: doorbell was lost and need to acquire it again */ GEM_BUG_ON(db->db_status != GUC_DOORBELL_ENABLED); -- 2.13.6 ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
