drm/i915/tgl: Fix TC-cold block/unblock sequence

The command register is the PCODE MBOX low register not the high one as
described by the spec. This left the system with the TC-cold power state
being blocked all the time. Fix things by using the correct register.

Also to make sure we retry a request for at least 600usec, when the
PCODE MBOX command itself succeeded, but the TC-cold block command
failed, sleep for 1msec unconditionally after any fail.

The change was tested with JTAG register read of the HW/FW's actual
TC-cold state, which reported the expected states after this change.

Tested-by: Nivedita Swaminathan <nivedita.swaminathan@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200805150056.24248-1-imre.deak@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/display/intel_display_power.c

@@ -3927,12 +3927,13 @@ tgl_tc_cold_request(struct drm_i915_private *i915, bool block)
 	int ret;
 
 	while (1) {
-		u32 low_val = 0, high_val;
+		u32 low_val;
+		u32 high_val = 0;
 
 		if (block)
-			high_val = TGL_PCODE_EXIT_TCCOLD_DATA_H_BLOCK_REQ;
+			low_val = TGL_PCODE_EXIT_TCCOLD_DATA_L_BLOCK_REQ;
 		else
-			high_val = TGL_PCODE_EXIT_TCCOLD_DATA_H_UNBLOCK_REQ;
+			low_val = TGL_PCODE_EXIT_TCCOLD_DATA_L_UNBLOCK_REQ;
 
 		/*
 		 * Spec states that we should timeout the request after 200us
@@ -3951,8 +3952,7 @@ tgl_tc_cold_request(struct drm_i915_private *i915, bool block)
 		if (++tries == 3)
 			break;
 
-		if (ret == -EAGAIN)
-			msleep(1);
+		msleep(1);
 	}
 
 	if (ret)

drivers/gpu/drm/i915/i915_reg.h

@@ -9226,8 +9226,8 @@ enum {
 #define   DISPLAY_IPS_CONTROL			0x19
 #define   TGL_PCODE_TCCOLD			0x26
 #define     TGL_PCODE_EXIT_TCCOLD_DATA_L_EXIT_FAILED	REG_BIT(0)
-#define     TGL_PCODE_EXIT_TCCOLD_DATA_H_BLOCK_REQ	0
-#define     TGL_PCODE_EXIT_TCCOLD_DATA_H_UNBLOCK_REQ	REG_BIT(0)
+#define     TGL_PCODE_EXIT_TCCOLD_DATA_L_BLOCK_REQ	0
+#define     TGL_PCODE_EXIT_TCCOLD_DATA_L_UNBLOCK_REQ	REG_BIT(0)
             /* See also IPS_CTL */
 #define     IPS_PCODE_CONTROL			(1 << 30)
 #define   HSW_PCODE_DYNAMIC_DUTY_CYCLE_CONTROL	0x1A