Quoting Animesh Manna (2019-08-21 07:32:25)
> DSB can program large set of data through indexed register write
> (opcode 0x9) in one shot. Will be using for bulk register programming
> e.g. gamma lut programming, HDR meta data programming.
>
> Cc: Shashank Sharma <shashank.sharma@xxxxxxxxx>
> Cc: Imre Deak <imre.deak@xxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
> Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
> Signed-off-by: Animesh Manna <animesh.manna@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_dsb.c | 42 ++++++++++++++++++++++++
> drivers/gpu/drm/i915/display/intel_dsb.h | 6 ++++
> 2 files changed, 48 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c b/drivers/gpu/drm/i915/display/intel_dsb.c
> index 8a9d082b1601..4fe8cac6246a 100644
> --- a/drivers/gpu/drm/i915/display/intel_dsb.c
> +++ b/drivers/gpu/drm/i915/display/intel_dsb.c
> @@ -22,6 +22,7 @@
> #define DSB_OPCODE_INDEXED_WRITE 0x9
> #define DSB_OPCODE_POLL 0xA
> #define DSB_BYTE_EN (0xf << 20)
> +#define DSB_REG_VALUE_MASK 0xfffff
>
> struct intel_dsb *
> intel_dsb_get(struct intel_crtc *crtc)
> @@ -79,6 +80,42 @@ intel_dsb_get(struct intel_crtc *crtc)
> return dsb;
> }
>
> +static void intel_dsb_indexed_reg_write(struct intel_dsb *dsb, i915_reg_t reg,
> + u32 val)
> +{
> + u32 *buf = dsb->cmd_buf;
> + u32 reg_val;
> +
> + reg_val = buf[dsb->ins_start_offset + 1] & DSB_REG_VALUE_MASK;
Uncached read.
> + if (reg_val != i915_mmio_reg_offset(reg)) {
> + /* Every instruction should be 8 byte aligned. */
> + if (dsb->free_pos & 0x1)
> + dsb->free_pos++;
dsb->free_pos = ALIGN(dsb->free_pos, 2);
> +
> + /* Update the size. */
> + dsb->ins_start_offset = dsb->free_pos;
> + 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]++;
Uncached read and write. So far this is working out to be _more_
expensive than mmio.
-Chris
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