drm/bridge: it6505: add AUX operation for HDCP KSV list read

HDCP KSV list readback can choose to use AUX FIFO or
general data register.
For some DisplayPort devices, the KSV list must be read
in 5 byte boundaries.
The original AUX read command does not support these devices.

The AUX command operation control register "REG_AUX_CMD_REQ" uses b[3:0]
as AUX operacion control, and b[7:4] are status bits and read only.
To change KSV read operation uses "CMD_AUX_NATIVE_READ" from using
the data registers to using AUX FIFO.
The extended command "CMD_AUX_GET_KSV_LIST" is added as
"CMD_AUX_NATIVE_READ" with the 0x10 flag which selects AUX FIFO mode.

Reviewed-by: Dmitry Baryshkov <[email protected]>
Signed-off-by: Hermes Wu <[email protected]>
Reviewed-by: AngeloGioacchino Del Regno <[email protected]>
Signed-off-by: Dmitry Baryshkov <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/20241230-v7-upstream-v7-3-e0fdd4844703@ite.corp-partner.google.com

Author: Hermes Wu

drivers/gpu/drm/bridge/ite-it6505.c

@@ -19,6 +19,7 @@
 #include <linux/regulator/consumer.h>
 #include <linux/types.h>
 #include <linux/wait.h>
+#include <linux/bitfield.h>
 
 #include <crypto/hash.h>
 
@@ -126,6 +127,7 @@
 #define REG_AUX_OUT_DATA0 0x27
 
 #define REG_AUX_CMD_REQ 0x2B
+#define M_AUX_REQ_CMD 0x0F
 #define AUX_BUSY BIT(5)
 
 #define REG_AUX_DATA_0_7 0x2C
@@ -324,6 +326,9 @@ enum aux_cmd_type {
 	CMD_AUX_NATIVE_READ = 0x0,
 	CMD_AUX_NATIVE_WRITE = 0x5,
 	CMD_AUX_I2C_EDID_READ = 0xB,
+
+	/* KSV read with AUX FIFO extend from CMD_AUX_NATIVE_READ*/
+	CMD_AUX_GET_KSV_LIST = 0x10,
 };
 
 enum aux_cmd_reply {
@@ -965,7 +970,8 @@ static ssize_t it6505_aux_operation(struct it6505 *it6505,
 	it6505_set_bits(it6505, REG_AUX_CTRL, AUX_USER_MODE, AUX_USER_MODE);
 
 aux_op_start:
-	if (cmd == CMD_AUX_I2C_EDID_READ) {
+	/* HW AUX FIFO supports only EDID and DCPD KSV FIFO area */
+	if (cmd == CMD_AUX_I2C_EDID_READ || cmd == CMD_AUX_GET_KSV_LIST) {
 		/* AUX EDID FIFO has max length of AUX_FIFO_MAX_SIZE bytes. */
 		size = min_t(size_t, size, AUX_FIFO_MAX_SIZE);
 		/* Enable AUX FIFO read back and clear FIFO */
@@ -996,7 +1002,7 @@ static ssize_t it6505_aux_operation(struct it6505 *it6505,
 				  size);
 
 	/* Aux Fire */
-	it6505_write(it6505, REG_AUX_CMD_REQ, cmd);
+	it6505_write(it6505, REG_AUX_CMD_REQ, FIELD_GET(M_AUX_REQ_CMD, cmd));
 
 	ret = it6505_aux_wait(it6505);
 	if (ret < 0)
@@ -1030,7 +1036,7 @@ static ssize_t it6505_aux_operation(struct it6505 *it6505,
 		goto aux_op_start;
 	}
 
-	if (cmd == CMD_AUX_I2C_EDID_READ) {
+	if (cmd == CMD_AUX_I2C_EDID_READ || cmd == CMD_AUX_GET_KSV_LIST) {
 		for (i = 0; i < size; i++) {
 			ret = it6505_read(it6505, REG_AUX_DATA_FIFO);
 			if (ret < 0)
@@ -1055,7 +1061,7 @@ static ssize_t it6505_aux_operation(struct it6505 *it6505,
 	ret = i;
 
 aux_op_err:
-	if (cmd == CMD_AUX_I2C_EDID_READ) {
+	if (cmd == CMD_AUX_I2C_EDID_READ || cmd == CMD_AUX_GET_KSV_LIST) {
 		/* clear AUX FIFO */
 		it6505_set_bits(it6505, REG_AUX_CTRL,
 				AUX_EN_FIFO_READ | CLR_EDID_FIFO,
@@ -1076,7 +1082,8 @@ static ssize_t it6505_aux_do_transfer(struct it6505 *it6505,
 				      size_t size, enum aux_cmd_reply *reply)
 {
 	int i, ret_size, ret = 0, request_size;
-	int fifo_max_size = (cmd == CMD_AUX_I2C_EDID_READ) ? AUX_FIFO_MAX_SIZE : 4;
+	int fifo_max_size = (cmd == CMD_AUX_I2C_EDID_READ || cmd == CMD_AUX_GET_KSV_LIST) ?
+						 AUX_FIFO_MAX_SIZE : 4;
 
 	mutex_lock(&it6505->aux_lock);
 	i = 0;