Added docbook info regarding Display State Buffer(DSB) which
is added from gen12 onwards to batch submit display HW programming.
v1: Initial version as RFC.
Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Acked-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Signed-off-by: Animesh Manna <animesh.manna@xxxxxxxxx>
---
Documentation/gpu/i915.rst | 9 ++++
drivers/gpu/drm/i915/display/intel_dsb.c | 68 ++++++++++++++++++++++++
2 files changed, 77 insertions(+)
diff --git a/Documentation/gpu/i915.rst b/Documentation/gpu/i915.rst
index 3415255ad3dc..38e31223a24c 100644
--- a/Documentation/gpu/i915.rst
+++ b/Documentation/gpu/i915.rst
@@ -246,6 +246,15 @@ Display PLLs
.. kernel-doc:: drivers/gpu/drm/i915/display/intel_dpll_mgr.h
:internal:
+Display State Buffer
+--------------------
+
+.. kernel-doc:: drivers/gpu/drm/i915/display/intel_dsb.c
+ :doc: DSB
+
+.. kernel-doc:: drivers/gpu/drm/i915/display/intel_dsb.c
+ :internal:
+
Memory Management and Command Submission
========================================
diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c b/drivers/gpu/drm/i915/display/intel_dsb.c
index bc1734072f34..501ff7f5db8c 100644
--- a/drivers/gpu/drm/i915/display/intel_dsb.c
+++ b/drivers/gpu/drm/i915/display/intel_dsb.c
@@ -9,6 +9,23 @@
#define DSB_BUF_SIZE (2 * PAGE_SIZE)
+/**
+ * DOC: DSB
+ *
+ * A DSB (Display State Buffer) is a queue of MMIO instructions in the memory
+ * which can be offloaded to DSB HW in Display Controller. DSB HW is a DMA
+ * engine that can be programmed to download the DSB from memory.
+ * It allows driver to batch submit display HW programming. This helps to
+ * reduce loading time and CPU activity, thereby making the context switch
+ * faster. DSB Support added from Gen12 Intel graphics based platform.
+ *
+ * DSB's can access only the pipe, plane, and transcoder Data Island Packet
+ * registers.
+ *
+ * DSB HW can support only register writes (both indexed and direct MMIO
+ * writes). There are no registers reads possible with DSB HW engine.
+ */
+
/* DSB opcodes. */
#define DSB_OPCODE_SHIFT 24
#define DSB_OPCODE_NOOP 0x0
@@ -73,6 +90,17 @@ static bool intel_dsb_disable_engine(struct intel_dsb *dsb)
return true;
}
+/**
+ * intel_dsb_get() - Allocate dsb context and return a dsb instance.
+ * @crtc: intel_crtc structure to get pipe info.
+ *
+ * This function will give handle of the DSB instance which
+ * user want to operate on.
+ *
+ * Return : address of Intel_dsb instance requested for.
+ * In failure case, the dsb instance will not have any command buffer.
+ */
+
struct intel_dsb *
intel_dsb_get(struct intel_crtc *crtc)
{
@@ -124,6 +152,14 @@ intel_dsb_get(struct intel_crtc *crtc)
return dsb;
}
+/**
+ * intel_dsb_put() - To destroy DSB context.
+ * @dsb: intel_dsb structure.
+ *
+ * This function is used to destroy the dsb-context by doing unpin
+ * and release the vma object.
+ */
+
void intel_dsb_put(struct intel_dsb *dsb)
{
struct intel_crtc *crtc;
@@ -146,6 +182,19 @@ void intel_dsb_put(struct intel_dsb *dsb)
}
}
+/**
+ * intel_dsb_indexed_reg_write() -Write to the dsb context for auto
+ * increment register.
+ * @dsb: intel_dsb structure.
+ * @reg: register address.
+ * @val: value.
+ *
+ * This function is used for auto-increment register and intel_dsb_reg_write()
+ * is used for normal register. During command buffer overflow, a warning
+ * is thrown and rest all erroneous condition register programming is done
+ * through mmio write.
+ */
+
void intel_dsb_indexed_reg_write(struct intel_dsb *dsb, i915_reg_t reg,
u32 val)
{
@@ -193,6 +242,18 @@ void intel_dsb_indexed_reg_write(struct intel_dsb *dsb, i915_reg_t reg,
buf[dsb->free_pos] = 0;
}
+/**
+ * intel_dsb_reg_write() -Write to the dsb context for normal
+ * register.
+ * @dsb: intel_dsb structure.
+ * @reg: register address.
+ * @val: value.
+ *
+ * This function is used for writing register-value pair in command
+ * buffer of DSB. During command buffer overflow, a warning
+ * is thrown and rest all erroneous condition register programming is done
+ * through mmio write.
+ */
void intel_dsb_reg_write(struct intel_dsb *dsb, i915_reg_t reg, u32 val)
{
struct intel_crtc *crtc = dsb->crtc;
@@ -215,6 +276,13 @@ void intel_dsb_reg_write(struct intel_dsb *dsb, i915_reg_t reg, u32 val)
i915_mmio_reg_offset(reg);
}
+/**
+ * intel_dsb_commit() - Trigger workload execution of DSB.
+ * @dsb: intel_dsb structure.
+ *
+ * This function is used to do actual write to hardware using DSB.
+ * On errors, fall back to MMIO. Also this function help to reset the context.
+ */
void intel_dsb_commit(struct intel_dsb *dsb)
{
struct intel_crtc *crtc = dsb->crtc;
