drm/i915/dsb: Indexed register write function for DSB.

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)
v5: reset ins_start_offset. (Jani)
v6: update ins_start_offset in inel_dsb_reg_write.

Cc: Shashank Sharma <shashank.sharma@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: NShashank Sharma <shashank.sharma@intel.com>
Signed-off-by: NAnimesh Manna <animesh.manna@intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190920115930.27829-5-animesh.manna@intel.com

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)
@@ -83,9 +85,74 @@ void intel_dsb_put(struct intel_dsb *dsb)
 		mutex_unlock(&i915->drm.struct_mutex);
 		dsb->cmd_buf = NULL;
 		dsb->free_pos = 0;
+		dsb->ins_start_offset = 0;
 	}
 }
 
+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;
+	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);
@@ -102,6 +169,7 @@ void intel_dsb_reg_write(struct intel_dsb *dsb, i915_reg_t reg, u32 val)
 		return;
 	}
 
+	dsb->ins_start_offset = dsb->free_pos;
 	buf[dsb->free_pos++] = val;
 	buf[dsb->free_pos++] = (DSB_OPCODE_MMIO_WRITE  << DSB_OPCODE_SHIFT) |
 			       (DSB_BYTE_EN << DSB_BYTE_EN_SHIFT) |

drivers/gpu/drm/i915/display/intel_dsb.h

@@ -32,11 +32,20 @@ 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 and help in identifying the batch 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