From: Ville Syrjälä Date: Fri, 23 May 2025 06:20:34 +0000 (+0530) Subject: drm/i915/dsb: Implement intel_dsb_gosub() X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2c41d62f6fb16d591df17b29edaa81ea56569bb3;p=thirdparty%2Flinux.git drm/i915/dsb: Implement intel_dsb_gosub() Add support for the new GOSUB DSB instruction (available on ptl+), which instructs the DSB to jump to a different buffer, execute the commands there, and then return execution to the next instruction in the original buffer. There are a few alignment related workarounds that need to be dealt with when emitting GOSUB instruction. v2: Right shift head and tail pointer passed to gosub command (chaitanya) v3: Add macro for right shifting head/tail pointers (Animesh) v4: Fix typo in commit message (Uma) Add comments explaining why right shifting htp is needed (Animesh) Signed-off-by: Ville Syrjälä Signed-off-by: Chaitanya Kumar Borah Reviewed-by: Uma Shankar Reviewed-by: Animesh Manna Signed-off-by: Animesh Manna Link: https://lore.kernel.org/r/20250523062041.166468-5-chaitanya.kumar.borah@intel.com --- diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c b/drivers/gpu/drm/i915/display/intel_dsb.c index 9b2de4e7e681e..cd32b59adf187 100644 --- a/drivers/gpu/drm/i915/display/intel_dsb.c +++ b/drivers/gpu/drm/i915/display/intel_dsb.c @@ -93,6 +93,10 @@ struct intel_dsb { /* see DSB_REG_VALUE_MASK */ #define DSB_OPCODE_POLL 0xA /* see DSB_REG_VALUE_MASK */ +#define DSB_OPCODE_GOSUB 0xC /* ptl+ */ +#define DSB_GOSUB_HEAD_SHIFT 26 +#define DSB_GOSUB_TAIL_SHIFT 0 +#define DSB_GOSUB_CONVERT_ADDR(x) ((x) >> 6) static bool pre_commit_is_vrr_active(struct intel_atomic_state *state, struct intel_crtc *crtc) @@ -533,6 +537,75 @@ static void intel_dsb_align_tail(struct intel_dsb *dsb) dsb->free_pos = aligned_tail / 4; } +static void intel_dsb_gosub_align(struct intel_dsb *dsb) +{ + u32 aligned_tail, tail; + + intel_dsb_ins_align(dsb); + + tail = dsb->free_pos * 4; + aligned_tail = ALIGN(tail, CACHELINE_BYTES); + + /* + * "The GOSUB instruction cannot be placed in + * cacheline QW slot 6 or 7 (numbered 0-7)" + */ + if (aligned_tail - tail <= 2 * 8) + intel_dsb_buffer_memset(&dsb->dsb_buf, dsb->free_pos, 0, + aligned_tail - tail); + + dsb->free_pos = aligned_tail / 4; +} + +void intel_dsb_gosub(struct intel_dsb *dsb, + struct intel_dsb *sub_dsb) +{ + struct intel_crtc *crtc = dsb->crtc; + struct intel_display *display = to_intel_display(crtc->base.dev); + unsigned int head, tail; + u64 head_tail; + + if (drm_WARN_ON(display->drm, dsb->id != sub_dsb->id)) + return; + + if (!assert_dsb_tail_is_aligned(sub_dsb)) + return; + + intel_dsb_gosub_align(dsb); + + head = intel_dsb_head(sub_dsb); + tail = intel_dsb_tail(sub_dsb); + + /* + * The GOSUB instruction has the following memory layout. + * + * +------------------------------------------------------------+ + * | Opcode | Rsvd | Head Ptr | Tail Ptr | + * | 0x0c | | | | + * +------------------------------------------------------------+ + * |<- 8bits->|<- 4bits ->|<-- 26bits -->|<-- 26bits -->| + * + * We have only 26 bits each to represent the head and tail + * pointers even though the addresses itself are of 32 bit. However, this + * is not a problem because the addresses are 64 bit aligned and therefore + * the last 6 bits are always Zero's. Therefore, we right shift the address + * by 6 before embedding it into the GOSUB instruction. + */ + + head_tail = ((u64)(DSB_GOSUB_CONVERT_ADDR(head)) << DSB_GOSUB_HEAD_SHIFT) | + ((u64)(DSB_GOSUB_CONVERT_ADDR(tail)) << DSB_GOSUB_TAIL_SHIFT); + + intel_dsb_emit(dsb, lower_32_bits(head_tail), + (DSB_OPCODE_GOSUB << DSB_OPCODE_SHIFT) | + upper_32_bits(head_tail)); + + /* + * "NOTE: the instructions within the cacheline + * FOLLOWING the GOSUB instruction must be NOPs." + */ + intel_dsb_align_tail(dsb); +} + void intel_dsb_finish(struct intel_dsb *dsb) { struct intel_crtc *crtc = dsb->crtc; diff --git a/drivers/gpu/drm/i915/display/intel_dsb.h b/drivers/gpu/drm/i915/display/intel_dsb.h index e843c52bf97c2..8b2cf0a7b7e68 100644 --- a/drivers/gpu/drm/i915/display/intel_dsb.h +++ b/drivers/gpu/drm/i915/display/intel_dsb.h @@ -57,6 +57,8 @@ void intel_dsb_vblank_evade(struct intel_atomic_state *state, void intel_dsb_poll(struct intel_dsb *dsb, i915_reg_t reg, u32 mask, u32 val, int wait_us, int count); +void intel_dsb_gosub(struct intel_dsb *dsb, + struct intel_dsb *sub_dsb); void intel_dsb_chain(struct intel_atomic_state *state, struct intel_dsb *dsb, struct intel_dsb *chained_dsb,