From 8b38b3a16719ee86f9aa2fd1bc479db7d5b28e48 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 9 Sep 2016 14:11:44 +0100 Subject: [PATCH] drm/i915: Compute the ELSP register location once Similar to the issue with reading from the context status buffer, see commit 26720ab97fea ("drm/i915: Move CSB MMIO reads out of the execlists lock"), we frequently write to the ELSP register (4 writes per interrupt) and know we hold the required spinlock and forcewake throughout. We can further reduce the cost of writing these registers beyond the I915_WRITE_FW() by precomputing the address of the ELSP register. We also note that the subsequent read serves no purpose here, and are happy to see it go. v2: Address I915_WRITE mistakes in changelog text data bss dec hex filename 1259784 4581 576 1264941 134d2d drivers/gpu/drm/i915/i915.ko 1259720 4581 576 1264877 134ced drivers/gpu/drm/i915/i915.ko Saves 64 bytes of address recomputation. Signed-off-by: Chris Wilson Reviewed-by: Mika Kuoppala Link: http://patchwork.freedesktop.org/patch/msgid/20160909131201.16673-4-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/intel_lrc.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index d7fa9b3a55c3..a6b9033203e5 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -331,10 +331,11 @@ uint64_t intel_lr_context_descriptor(struct i915_gem_context *ctx, static void execlists_elsp_write(struct drm_i915_gem_request *rq0, struct drm_i915_gem_request *rq1) { - struct intel_engine_cs *engine = rq0->engine; struct drm_i915_private *dev_priv = rq0->i915; - uint64_t desc[2]; + u32 __iomem *elsp = + dev_priv->regs + i915_mmio_reg_offset(RING_ELSP(engine)); + u64 desc[2]; if (rq1) { desc[1] = intel_lr_context_descriptor(rq1->ctx, rq1->engine); @@ -347,15 +348,12 @@ static void execlists_elsp_write(struct drm_i915_gem_request *rq0, rq0->elsp_submitted++; /* You must always write both descriptors in the order below. */ - I915_WRITE_FW(RING_ELSP(engine), upper_32_bits(desc[1])); - I915_WRITE_FW(RING_ELSP(engine), lower_32_bits(desc[1])); + writel(upper_32_bits(desc[1]), elsp); + writel(lower_32_bits(desc[1]), elsp); - I915_WRITE_FW(RING_ELSP(engine), upper_32_bits(desc[0])); + writel(upper_32_bits(desc[0]), elsp); /* The context is automatically loaded after the following */ - I915_WRITE_FW(RING_ELSP(engine), lower_32_bits(desc[0])); - - /* ELSP is a wo register, use another nearby reg for posting */ - POSTING_READ_FW(RING_EXECLIST_STATUS_LO(engine)); + writel(lower_32_bits(desc[0]), elsp); } static void -- 2.20.1