[PATCH 1/2] drm/hyperv: add modes for all resolutions offered by the host

[Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>]

The host reports the resolutions it supports, which depend on the VM's
configuration: a list of standard resolutions by default, those up to a
maximum plus the maximum itself, or a single resolution. The driver
only takes the largest and the default resolution from the list, and
offers the DMT modes of up to 60 Hz that fit. Resolutions without such
a mode are thus missing (e.g. 1152x864, for which DMT only has a 75 Hz
mode). A VM set to 2560x1440 even ends up without a preferred mode, as
DMT has no 2560x1440 mode at all.

So, keep the list and add a 60 Hz CVT mode for every resolution in it
that lacks a mode of its size, so that all of them can be used. CVT
rounds the width down to a multiple of 8 while the host only requires an
even width (e.g. 1366x768), so restore the width afterwards.

Signed-off-by: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
---
 drivers/gpu/drm/hyperv/hyperv_drm.h         |  9 +++++++
 drivers/gpu/drm/hyperv/hyperv_drm_modeset.c | 29 +++++++++++++++++++++
 drivers/gpu/drm/hyperv/hyperv_drm_proto.c   | 10 +++----
 3 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/hyperv/hyperv_drm.h b/drivers/gpu/drm/hyperv/hyperv_drm.h
index df03185a2e19..6006d665343b 100644
--- a/drivers/gpu/drm/hyperv/hyperv_drm.h
+++ b/drivers/gpu/drm/hyperv/hyperv_drm.h
@@ -19,6 +19,13 @@
 #define SYNTHVID_CURSOR_MAX_SIZE (SYNTHVID_CURSOR_MAX_X * \
 	SYNTHVID_CURSOR_MAX_Y * SYNTHVID_CURSOR_ARGB_PIXEL_SIZE)
 
+#define SYNTHVID_MAX_RESOLUTION_COUNT 64
+
+struct hvd_screen_info {
+	u16 width;
+	u16 height;
+} __packed;
+
 /*
  * Copy of the cursor last handed to the host, so that it can be sent again
  * when needed, e.g. after a VM Connection window was opened.
@@ -55,6 +62,8 @@ struct hv_drm_device {
 	u32 preferred_width;
 	u32 preferred_height;
 	u32 screen_depth;
+	struct hvd_screen_info resolutions[SYNTHVID_MAX_RESOLUTION_COUNT];
+	unsigned int resolution_count;
 
 	/* hw */
 	struct resource *mem;
diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c b/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
index 48d7751c0bdd..177f804dca0c 100644
--- a/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
+++ b/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
@@ -46,14 +46,43 @@ static int hv_drm_blit_to_vram_rect(struct drm_framebuffer *fb,
 	return 0;
 }
 
+static int hv_drm_connector_add_mode(struct drm_connector *connector,
+				     u16 width, u16 height)
+{
+	struct drm_display_mode *mode;
+
+	list_for_each_entry(mode, &connector->probed_modes, head) {
+		if (mode->hdisplay == width && mode->vdisplay == height)
+			return 0;
+	}
+
+	mode = drm_cvt_mode(connector->dev, width, height, 60, false, false,
+			    false);
+	if (!mode)
+		return 0;
+
+	/* CVT rounds the width down to a multiple of 8, the host does not */
+	mode->hdisplay = width;
+	mode->type |= DRM_MODE_TYPE_DRIVER;
+	drm_mode_set_name(mode);
+	drm_mode_probed_add(connector, mode);
+
+	return 1;
+}
+
 static int hv_drm_connector_get_modes(struct drm_connector *connector)
 {
 	struct hv_drm_device *hv = to_hv_drm(connector->dev);
+	unsigned int i;
 	int count;
 
 	count = drm_add_modes_noedid(connector,
 				     connector->dev->mode_config.max_width,
 				     connector->dev->mode_config.max_height);
+	for (i = 0; i < hv->resolution_count; i++)
+		count += hv_drm_connector_add_mode(connector,
+						   hv->resolutions[i].width,
+						   hv->resolutions[i].height);
 	drm_set_preferred_mode(connector, hv->preferred_width,
 			       hv->preferred_height);
 
diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
index 99e036576929..81ffb88ba6a1 100644
--- a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
+++ b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
@@ -56,11 +56,6 @@ struct pipe_msg_hdr {
 	u32 size; /* size of message after this field */
 } __packed;
 
-struct hvd_screen_info {
-	u16 width;
-	u16 height;
-} __packed;
-
 struct synthvid_msg_hdr {
 	u32 type;
 	u32 size;  /* size of this header + payload after this field */
@@ -145,7 +140,6 @@ struct synthvid_dirt {
 } __packed;
 
 #define SYNTHVID_EDID_BLOCK_SIZE	128
-#define	SYNTHVID_MAX_RESOLUTION_COUNT	64
 
 struct synthvid_supported_resolution_req {
 	u8 maximum_resolution_count;
@@ -522,6 +516,10 @@ static int hv_drm_get_supported_resolution(struct hv_device *hdev)
 	hv->preferred_height =
 		msg->resolution_resp.supported_resolution[index].height;
 
+	hv->resolution_count = msg->resolution_resp.resolution_count;
+	memcpy(hv->resolutions, msg->resolution_resp.supported_resolution,
+	       hv->resolution_count * sizeof(hv->resolutions[0]));
+
 	return 0;
 }
 
-- 
2.56.0