From c18ef81e79c2beccc5738e564fb56f1b78d2d5fc Mon Sep 17 00:00:00 2001
From: Girish Pathak <girish.pathak at arm.com>
Date: Tue, 26 Sep 2017 21:15:21 +0100
Subject: [PATCH] ArmPlatformPkg: Implement LcdIdentify function for HDLCD GOP

LcdIdentify function does not currently check presence of HDLCD
controller.

Implement this functionality by reading HDLCD_REG_VERSION and checking
against the PRODUCT_ID field to detect presence of HDLCD controller.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Girish Pathak <girish.pathak@arm.com>
Signed-off-by: Evan Lloyd <evan.lloyd@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
---
 ArmPlatformPkg/Library/HdLcd/HdLcd.c | 8 +++++++-
 ArmPlatformPkg/Library/HdLcd/HdLcd.h | 2 ++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/ArmPlatformPkg/Library/HdLcd/HdLcd.c b/ArmPlatformPkg/Library/HdLcd/HdLcd.c
index 28306c530e..039048398c 100644
--- a/ArmPlatformPkg/Library/HdLcd/HdLcd.c
+++ b/ArmPlatformPkg/Library/HdLcd/HdLcd.c
@@ -175,11 +175,17 @@ LcdShutdown (
 
   @retval EFI_SUCCESS            Returns success if platform implements a HDLCD
                                  controller.
+  @retval EFI_NOT_FOUND          HDLCD display controller not found on the
+                                 platform.
 **/
 EFI_STATUS
 LcdIdentify (
   VOID
   )
 {
-  return EFI_SUCCESS;
+  if ((MmioRead32 (HDLCD_REG_VERSION) >> 16) == HDLCD_PRODUCT_ID) {
+    return EFI_SUCCESS;
+  }
+
+  return EFI_NOT_FOUND;
 }
diff --git a/ArmPlatformPkg/Library/HdLcd/HdLcd.h b/ArmPlatformPkg/Library/HdLcd/HdLcd.h
index cd2c0366c7..1efa78eedc 100644
--- a/ArmPlatformPkg/Library/HdLcd/HdLcd.h
+++ b/ArmPlatformPkg/Library/HdLcd/HdLcd.h
@@ -85,4 +85,6 @@
 // Number of bytes per pixel
 #define HDLCD_4BYTES_PER_PIXEL           ((4 - 1) << 3)
 
+#define HDLCD_PRODUCT_ID                 0x1CDC
+
 #endif /* HDLCD_H_ */