On Wed, 18 Sep 2019, Animesh Manna <animesh.ma...@intel.com> wrote:
> DSB can program large set of data through indexed register write
> (opcode 0x9) in one shot. DSB feature can be used for bulk register
> programming e.g. gamma lut programming, HDR meta data programming.
>
> v1: initial version.
> v2: simplified code by using ALIGN(). (Chris)
> v3: ascii table added as code comment. (Shashank)
> v4: cosmetic changes done. (Shashank)
>
> Cc: Shashank Sharma <shashank.sha...@intel.com>
> Cc: Imre Deak <imre.d...@intel.com>
> Cc: Jani Nikula <jani.nik...@intel.com>
> Cc: Rodrigo Vivi <rodrigo.v...@intel.com>
> Reviewed-by: Shashank Sharma <shashank.sha...@intel.com>
> Signed-off-by: Animesh Manna <animesh.ma...@intel.com>
> ---
> drivers/gpu/drm/i915/display/intel_dsb.c | 66 ++++++++++++++++++++++++
> drivers/gpu/drm/i915/display/intel_dsb.h | 8 +++
> 2 files changed, 74 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c
> b/drivers/gpu/drm/i915/display/intel_dsb.c
> index f94cd6dc98b6..2d80e452e284 100644
> --- a/drivers/gpu/drm/i915/display/intel_dsb.c
> +++ b/drivers/gpu/drm/i915/display/intel_dsb.c
> @@ -12,8 +12,10 @@
> /* DSB opcodes. */
> #define DSB_OPCODE_SHIFT 24
> #define DSB_OPCODE_MMIO_WRITE 0x1
> +#define DSB_OPCODE_INDEXED_WRITE 0x9
> #define DSB_BYTE_EN 0xF
> #define DSB_BYTE_EN_SHIFT 20
> +#define DSB_REG_VALUE_MASK 0xfffff
>
> struct intel_dsb *
> intel_dsb_get(struct intel_crtc *crtc)
> @@ -86,6 +88,70 @@ void intel_dsb_put(struct intel_dsb *dsb)
> }
> }
>
> +void intel_dsb_indexed_reg_write(struct intel_dsb *dsb, i915_reg_t reg,
> + u32 val)
> +{
> + struct intel_crtc *crtc = container_of(dsb, typeof(*crtc), dsb);
> + struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> + u32 *buf = dsb->cmd_buf;
> + u32 reg_val;
> +
> + if (!buf) {
> + I915_WRITE(reg, val);
> + return;
> + }
> +
> + if (WARN_ON(dsb->free_pos >= DSB_BUF_SIZE)) {
> + DRM_DEBUG_KMS("DSB buffer overflow\n");
> + return;
> + }
> +
> + /*
> + * For example the buffer will look like below for 3 dwords for auto
> + * increment register:
> + * +--------------------------------------------------------+
> + * | size = 3 | offset &| value1 | value2 | value3 | zero |
> + * | | opcode | | | | |
> + * +--------------------------------------------------------+
> + * + + + + + + +
> + * 0 4 8 12 16 20 24
> + * Byte
> + *
> + * As every instruction is 8 byte aligned the index of dsb instruction
> + * will start always from even number while dealing with u32 array. If
> + * we are writing odd no of dwords, Zeros will be added in the end for
> + * padding.
> + */
> + reg_val = buf[dsb->ins_start_offset + 1] & DSB_REG_VALUE_MASK;
dsb->ins_start_offset is never reset anywhere.
Imagine you do:
intel_dsb_indexed_reg_write(dsb, FOO, 0);
intel_dsb_indexed_reg_write(dsb, FOO, 0);
intel_dsb_reg_write(dsb, BAR, 0);
intel_dsb_indexed_reg_write(dsb, FOO, 0);
The last one will screw up the previous indexed writes.
BR,
Jani.
> + if (reg_val != i915_mmio_reg_offset(reg)) {
> + /* Every instruction should be 8 byte aligned. */
> + dsb->free_pos = ALIGN(dsb->free_pos, 2);
> +
> + dsb->ins_start_offset = dsb->free_pos;
> +
> + /* Update the size. */
> + buf[dsb->free_pos++] = 1;
> +
> + /* Update the opcode and reg. */
> + buf[dsb->free_pos++] = (DSB_OPCODE_INDEXED_WRITE <<
> + DSB_OPCODE_SHIFT) |
> + i915_mmio_reg_offset(reg);
> +
> + /* Update the value. */
> + buf[dsb->free_pos++] = val;
> + } else {
> + /* Update the new value. */
> + buf[dsb->free_pos++] = val;
> +
> + /* Update the size. */
> + buf[dsb->ins_start_offset]++;
> + }
> +
> + /* if number of data words is odd, then the last dword should be 0.*/
> + if (dsb->free_pos & 0x1)
> + buf[dsb->free_pos] = 0;
> +}
> +
> 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);
> diff --git a/drivers/gpu/drm/i915/display/intel_dsb.h
> b/drivers/gpu/drm/i915/display/intel_dsb.h
> index 0686d67b34d5..d6ced4422814 100644
> --- a/drivers/gpu/drm/i915/display/intel_dsb.h
> +++ b/drivers/gpu/drm/i915/display/intel_dsb.h
> @@ -30,11 +30,19 @@ struct intel_dsb {
> * and help in calculating tail of command buffer.
> */
> int free_pos;
> +
> + /*
> + * ins_start_offset will help to store start address
> + * of the dsb instuction of auto-increment register.
> + */
> + u32 ins_start_offset;
> };
>
> struct intel_dsb *
> intel_dsb_get(struct intel_crtc *crtc);
> void intel_dsb_put(struct intel_dsb *dsb);
> void intel_dsb_reg_write(struct intel_dsb *dsb, i915_reg_t reg, u32 val);
> +void intel_dsb_indexed_reg_write(struct intel_dsb *dsb, i915_reg_t reg,
> + u32 val);
>
> #endif
--
Jani Nikula, Intel Open Source Graphics Center
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