drm/i915/dsb: Add support for GOSUB interrupt

DSB raises an interrupt when there is a nested GOSUB command or
illegal Head/Tail. Add support to log such errors in the DSB
interrupt handler.

v2: Enable support only in platforms that support this (Ville)

Signed-off-by: Chaitanya Kumar Borah <[e-mail]>
Reviewed-by: Uma Shankar <[e-mail]>
Signed-off-by: Animesh Manna <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

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

···
 	if (DISPLAY_VER(display) >= 14)
 		errors |= DSB_ATS_FAULT_INT_STATUS;
 
+	if (DISPLAY_VER(display) >= 30)
+		errors |= DSB_GOSUB_INT_STATUS;
+
 	return errors;
 }
 
···
 
 	if (DISPLAY_VER(display) >= 14)
 		errors |= DSB_ATS_FAULT_INT_EN;
+
+	if (DISPLAY_VER(display) >= 30)
+		errors |= DSB_GOSUB_INT_EN;
 
 	return errors;
 }
···
 			crtc->base.base.id, crtc->base.name, dsb_id);
 	if (errors & DSB_POLL_ERR_INT_STATUS)
 		drm_err(display->drm, "[CRTC:%d:%s] DSB %d poll error\n",
+			crtc->base.base.id, crtc->base.name, dsb_id);
+	if (errors & DSB_GOSUB_INT_STATUS)
+		drm_err(display->drm, "[CRTC:%d:%s] DSB %d GOSUB programming error\n",
 			crtc->base.base.id, crtc->base.name, dsb_id);
 }

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

···
 #define   DSB_RESET_SM_STATE_MASK	REG_GENMASK(5, 4)
 #define   DSB_RUN_SM_STATE_MASK		REG_GENMASK(2, 0)
 #define DSB_INTERRUPT(pipe, id)		_MMIO(DSBSL_INSTANCE(pipe, id) + 0x28)
+#define   DSB_GOSUB_INT_EN		REG_BIT(21) /* ptl+ */
 #define   DSB_ATS_FAULT_INT_EN		REG_BIT(20) /* mtl+ */
 #define   DSB_GTT_FAULT_INT_EN		REG_BIT(19)
 #define   DSB_RSPTIMEOUT_INT_EN		REG_BIT(18)
 #define   DSB_POLL_ERR_INT_EN		REG_BIT(17)
 #define   DSB_PROG_INT_EN		REG_BIT(16)
+#define   DSB_GOSUB_INT_STATUS		REG_BIT(5) /* ptl+ */
 #define   DSB_ATS_FAULT_INT_STATUS	REG_BIT(4) /* mtl+ */
 #define   DSB_GTT_FAULT_INT_STATUS	REG_BIT(3)
 #define   DSB_RSPTIMEOUT_INT_STATUS	REG_BIT(2)