[PATCH v2 4/6] drm_hyperv: Remove support for synth video protocol of old Hyper-V hosts

With the overall removal of Linux support for running on Hyper-V
hosts earlier than WS2016 and Windows 10, it's no longer necessary
to support older synthetic video protocols. Remove the support.

Signed-off-by: Michael Kelley <[email protected]>
---
Changes in v2:
* Removed now unused function hv_drm_version_ge() and field
  synthvid_version. While it's posssible that these might be needed
  again if a new synthetic frame buffer protocol version is introduced,
  my sense is that this is not an area of active development on the
  Hyper-V side, so a new protocol version is less likely. The
  function/field can be added back when/if needed. [Sashiko]

 drivers/gpu/drm/hyperv/hyperv_drm.h       |  1 -
 drivers/gpu/drm/hyperv/hyperv_drm_proto.c | 44 ++++++-----------------
 2 files changed, 10 insertions(+), 35 deletions(-)

diff --git a/drivers/gpu/drm/hyperv/hyperv_drm.h b/drivers/gpu/drm/hyperv/hyperv_drm.h
index 78136ec2c2f4..29e6f54af15f 100644
--- a/drivers/gpu/drm/hyperv/hyperv_drm.h
+++ b/drivers/gpu/drm/hyperv/hyperv_drm.h
@@ -29,7 +29,6 @@ struct hv_drm_device {
 	unsigned long fb_base;
 	unsigned long fb_size;
 	struct completion wait;
-	u32 synthvid_version;
 	u32 mmio_megabytes;
 	bool dirt_needed;
 
diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
index f0ef627b4898..1d09bba1efdd 100644
--- a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
+++ b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
@@ -17,7 +17,7 @@
 #define SYNTHVID_VER_GET_MAJOR(ver) (ver & 0x0000ffff)
 #define SYNTHVID_VER_GET_MINOR(ver) ((ver & 0xffff0000) >> 16)
 
-/* Support for VERSION_WIN7 is removed. #define is retained for reference. */
+/* Support for WIN7 and WIN8 is removed. #define's retained for reference. */
 #define SYNTHVID_VERSION_WIN7 SYNTHVID_VERSION(3, 0)
 #define SYNTHVID_VERSION_WIN8 SYNTHVID_VERSION(3, 2)
 #define SYNTHVID_VERSION_WIN10 SYNTHVID_VERSION(3, 5)
@@ -181,16 +181,6 @@ struct synthvid_msg {
 	};
 } __packed;
 
-static inline bool hv_drm_version_ge(u32 ver1, u32 ver2)
-{
-	if (SYNTHVID_VER_GET_MAJOR(ver1) > SYNTHVID_VER_GET_MAJOR(ver2) ||
-	    (SYNTHVID_VER_GET_MAJOR(ver1) == SYNTHVID_VER_GET_MAJOR(ver2) &&
-	     SYNTHVID_VER_GET_MINOR(ver1) >= SYNTHVID_VER_GET_MINOR(ver2)))
-		return true;
-
-	return false;
-}
-
 static inline int hv_drm_sendpacket(struct hv_device *hdev, struct synthvid_msg *msg)
 {
 	static atomic64_t request_id = ATOMIC64_INIT(0);
@@ -236,7 +226,6 @@ static int hv_drm_negotiate_version(struct hv_device *hdev, u32 ver)
 		return -ENODEV;
 	}
 
-	hv->synthvid_version = ver;
 	drm_info(dev, "Synthvid Version major %d, minor %d\n",
 		 SYNTHVID_VER_GET_MAJOR(ver), SYNTHVID_VER_GET_MINOR(ver));
 
@@ -557,23 +546,12 @@ int hv_drm_connect_vsp(struct hv_device *hdev)
 		return ret;
 	}
 
-	/* Negotiate the protocol version with host */
-	switch (vmbus_proto_version) {
-	case VERSION_WIN10:
-	case VERSION_WIN10_V5:
-		ret = hv_drm_negotiate_version(hdev, SYNTHVID_VERSION_WIN10);
-		if (!ret)
-			break;
-		fallthrough;
-	case VERSION_WIN8:
-	case VERSION_WIN8_1:
-		ret = hv_drm_negotiate_version(hdev, SYNTHVID_VERSION_WIN8);
-		break;
-	default:
-		ret = hv_drm_negotiate_version(hdev, SYNTHVID_VERSION_WIN10);
-		break;
-	}
-
+	/*
+	 * Negotiate the protocol version with host. Since support for hosts
+	 * older than WIN10 has been removed from Linux, only negotiate the
+	 * WIN10 version.
+	 */
+	ret = hv_drm_negotiate_version(hdev, SYNTHVID_VERSION_WIN10);
 	if (ret) {
 		drm_err(dev, "Synthetic video device version not accepted %d\n", ret);
 		goto error;
@@ -581,11 +559,9 @@ int hv_drm_connect_vsp(struct hv_device *hdev)
 
 	hv->screen_depth = SYNTHVID_DEPTH_WIN8;
 
-	if (hv_drm_version_ge(hv->synthvid_version, SYNTHVID_VERSION_WIN10)) {
-		ret = hv_drm_get_supported_resolution(hdev);
-		if (ret)
-			drm_err(dev, "Failed to get supported resolution from host, use default\n");
-	}
+	ret = hv_drm_get_supported_resolution(hdev);
+	if (ret)
+		drm_err(dev, "Failed to get supported resolution from host, use default\n");
 
 	if (!hv->screen_width_max) {
 		hv->screen_width_max = SYNTHVID_WIDTH_WIN8;
-- 
2.25.1