pvr: drop master for the display FD if it's not needed

Currently the display FD is opened twice because of pvr_winsys_create()
being called twice, however the WSI (which will do modeset on the
display FD in case of VK_KHR_display) is registered against the winsys
created at PhysicalDevice enumeration time, and the display FD opened at
Device creation time will only be used for allocating dumb buffer (which
does not require master privilege).

Add a parameter to pvr_winsys_create() to indicate whether the master
privilege is desired on the display FD, and pass true only when creating
the winsys for PhysicalDevice initialization.

Fixes VK_KHR_display operation on PowerVR driver, which is broken after
the WSI code starts to drop master in commit 870e233ca5
("vulkan/wsi/display: Avoid holding drm master for the device's fd.").

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/15161
Signed-off-by: Icenowy Zheng <zhengxingda@iscas.ac.cn>
Reviewed-by: Frank Binns <frank.binns@imgtec.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/40640>

src/imagination/vulkan/pvr_arch_device.c

@@ -703,7 +703,7 @@ VkResult PVR_PER_ARCH(create_device)(struct pvr_physical_device *pdevice,
    assert(pCreateInfo->sType == VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO);
 
    result = pvr_winsys_create(pdevice->render_path,
-                              pdevice->display_path,
+                              pdevice->display_path, false,
                               pAllocator ? pAllocator : &instance->vk.alloc,
                               &ws);
    if (result != VK_SUCCESS)

src/imagination/vulkan/pvr_physical_device.c

@@ -1031,7 +1031,8 @@ VkResult pvr_physical_device_init(struct pvr_physical_device *pdevice,
    pdevice->render_devid = render_stat.st_rdev;
 
    result =
-      pvr_winsys_create(render_path, display_path, &instance->vk.alloc, &ws);
+      pvr_winsys_create(render_path, display_path, true,
+                        &instance->vk.alloc, &ws);
    if (result != VK_SUCCESS)
       goto err_vk_free_display_path;
 

src/imagination/vulkan/winsys/pvr_winsys.c

@@ -50,6 +50,7 @@ void pvr_winsys_destroy(struct pvr_winsys *ws)
 
 VkResult pvr_winsys_create(const char *render_path,
                            const char *display_path,
+                           bool keep_display_master,
                            const VkAllocationCallbacks *alloc,
                            struct pvr_winsys **const ws_out)
 {
@@ -76,6 +77,12 @@ VkResult pvr_winsys_create(const char *render_path,
                             display_path);
          goto err_close_render_fd;
       }
+      if (!keep_display_master) {
+         /* Try to drop master for the display FD if it's not meant to be
+          * kept, but not to fail if it's not the master at opening time.
+          */
+         drmDropMaster(display_fd);
+      }
    } else {
       display_fd = -1;
    }

src/imagination/vulkan/winsys/pvr_winsys.h

@@ -476,6 +476,7 @@ struct pvr_winsys {
 void pvr_winsys_destroy(struct pvr_winsys *ws);
 VkResult pvr_winsys_create(const char *render_path,
                            const char *display_path,
+                           bool keep_display_master,
                            const VkAllocationCallbacks *alloc,
                            struct pvr_winsys **ws_out);