[PATCH] drm/udl: Fix for the X server screen update

[poma]

Fix for DisplayLink GPU USB2.0 device X server screen update

Within X server on top of DisplayLink GPU USB2.0 device,
screen content is not refreshed i.e. updated,
which is the most basic functionality of the screen.

This partially (udl_handle_damage()) reverts commit:

- e375882406d0cc24030746638592004755ed4ae0
  "drm/udl: Use drm_fb_helper deferred_io support"

Thanks Noralf for the tip.

$ modinfo udl
filename:       /lib/modules/4.7.4-234.fc24.x86_64/updates/udl.ko
license:        GPL
alias:          usb:v17E9p*d*dc*dsc*dp*icFFisc00ip00in*
depends:        
intree:         Y
vermagic:       4.7.4-234.fc24.x86_64 SMP mod_unload 
parm:           fb_bpp:int
parm:           fb_defio:int

$ dmesg | grep udl
[   41.888469] udl: module verification failed: signature and/or required key 
missing - tainting kernel
[   42.156988] udl 1-2:1.0: fb1: udldrmfb frame buffer device
[   42.158940] [drm] Initialized udl on minor 1
[   42.159676] usbcore: registered new interface driver udl

$ grep udl /var/log/Xorg.0.log
[    71.194] (**) |   |-->Device "udl0"

Tested-by: poma <poma at gmail.com>
---
 drivers/gpu/drm/udl/udl_drv.h |  2 ++
 drivers/gpu/drm/udl/udl_fb.c  | 39 +++++++++++++++++++++++++++++++++++++--
 2 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/udl/udl_drv.h b/drivers/gpu/drm/udl/udl_drv.h
index 0b03d34..4a064ef 100644
--- a/drivers/gpu/drm/udl/udl_drv.h
+++ b/drivers/gpu/drm/udl/udl_drv.h
@@ -81,6 +81,8 @@ struct udl_framebuffer {
        struct drm_framebuffer base;
        struct udl_gem_object *obj;
        bool active_16; /* active on the 16-bit channel */
+       int x1, y1, x2, y2; /* dirty rect */
+       spinlock_t dirty_lock;
 };

 #define to_udl_fb(x) container_of(x, struct udl_framebuffer, base)
diff --git a/drivers/gpu/drm/udl/udl_fb.c b/drivers/gpu/drm/udl/udl_fb.c
index d5df555..b2b42d2 100644
--- a/drivers/gpu/drm/udl/udl_fb.c
+++ b/drivers/gpu/drm/udl/udl_fb.c
@@ -90,6 +90,9 @@ int udl_handle_damage(struct udl_framebuffer *fb, int x, int 
y,
        struct urb *urb;
        int aligned_x;
        int bpp = (fb->base.bits_per_pixel / 8);
+       int x2, y2;
+       bool store_for_later = false;
+       unsigned long flags;

        if (!fb->active_16)
                return 0;
@@ -115,6 +118,38 @@ int udl_handle_damage(struct udl_framebuffer *fb, int x, 
int y,
            (y + height > fb->base.height))
                return -EINVAL;

+       /* if we are in atomic just store the info
+          can't test inside spin lock */
+       if (in_atomic())
+               store_for_later = true;
+
+       x2 = x + width - 1;
+       y2 = y + height - 1;
+
+       spin_lock_irqsave(&fb->dirty_lock, flags);
+
+       if (fb->y1 < y)
+               y = fb->y1;
+       if (fb->y2 > y2)
+               y2 = fb->y2;
+       if (fb->x1 < x)
+               x = fb->x1;
+       if (fb->x2 > x2)
+               x2 = fb->x2;
+
+       if (store_for_later) {
+               fb->x1 = x;
+               fb->x2 = x2;
+               fb->y1 = y;
+               fb->y2 = y2;
+               spin_unlock_irqrestore(&fb->dirty_lock, flags);
+               return 0;
+       }
+
+       fb->x1 = fb->y1 = INT_MAX;
+       fb->x2 = fb->y2 = 0;
+
+       spin_unlock_irqrestore(&fb->dirty_lock, flags);
        start_cycles = get_cycles();

        urb = udl_get_urb(dev);
@@ -122,14 +157,14 @@ int udl_handle_damage(struct udl_framebuffer *fb, int x, 
int y,
                return 0;
        cmd = urb->transfer_buffer;

-       for (i = y; i < height ; i++) {
+       for (i = y; i <= y2 ; i++) {
                const int line_offset = fb->base.pitches[0] * i;
                const int byte_offset = line_offset + (x * bpp);
                const int dev_byte_offset = (fb->base.width * bpp * i) + (x * 
bpp);
                if (udl_render_hline(dev, bpp, &urb,
                                     (char *) fb->obj->vmapping,
                                     &cmd, byte_offset, dev_byte_offset,
-                                    width * bpp,
+                                    (x2 - x + 1) * bpp,
                                     &bytes_identical, &bytes_sent))
                        goto error;
        }
-- 
2.7.4