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drm/i915/dsb: Documentation for DSB.

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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@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Shashank Sharma <shashank.sharma@intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190920115930.27829-11-animesh.manna@intel.com
This commit is contained in:
Animesh Manna 2019-09-20 17:29:30 +05:30 committed by Jani Nikula
parent dfaa6f285b
commit 5dd85e72bc
2 changed files with 77 additions and 0 deletions
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9
Documentation/gpu/i915.rst
View file

@ -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
========================================

68
drivers/gpu/drm/i915/display/intel_dsb.c
View file

@ -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_MMIO_WRITE 0x1
@ -66,6 +83,17 @@ static inline 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 provides handle of a DSB instance, for the further DSB
* operations.
*
* Returns: address of Intel_dsb instance requested for.
* Failure: Returns the same DSB instance, but without a command buffer.
*/
struct intel_dsb *
intel_dsb_get(struct intel_crtc *crtc)
{
@ -116,6 +144,14 @@ intel_dsb_get(struct intel_crtc *crtc)
return dsb;
}
/**
* intel_dsb_put() - To destroy DSB context.
* @dsb: intel_dsb structure.
*
* This function destroys the DSB context allocated by a dsb_get(), by
* unpinning and releasing the VMA object associated with it.
*/
void intel_dsb_put(struct intel_dsb *dsb)
{
struct intel_crtc *crtc = container_of(dsb, typeof(*crtc), dsb);
@ -138,6 +174,19 @@ 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 writing register-value pair in command
* buffer of DSB for auto-increment 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)
{
@ -202,6 +251,18 @@ 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 = container_of(dsb, typeof(*crtc), dsb);
@ -225,6 +286,13 @@ 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 = container_of(dsb, typeof(*crtc), dsb);