kernel/drivers/video/fbdev/udlfb.c, branch linux-5.1.y

udlfb: introduce a rendering mutex

2019-05-25T16:16:34Z

commit babc250e278eac7b0e671bdaedf833759b43bb78 upstream. Rendering calls may be done simultaneously from the workqueue, dlfb_ops_write, dlfb_ops_ioctl, dlfb_ops_set_par and dlfb_dpy_deferred_io. The code is robust enough so that it won't crash on concurrent rendering. However, concurrent rendering may cause display corruption if the same pixel is simultaneously being rendered. In order to avoid this corruption, this patch adds a mutex around the rendering calls. Signed-off-by: Mikulas Patocka Cc: Bernie Thompson Cc: Ladislav Michl Cc: [b.zolnierkie: replace "dlfb:" with "uldfb:" in the patch summary] Signed-off-by: Bartlomiej Zolnierkiewicz Signed-off-by: Greg Kroah-Hartman

udlfb: fix sleeping inside spinlock

2019-05-25T16:16:33Z

commit 6b11f9d8433b471fdd3ebed232b43a4b723be6ff upstream. If a framebuffer device is used as a console, the rendering calls (copyarea, fillrect, imageblit) may be done with the console spinlock held. On udlfb, these function call dlfb_handle_damage that takes a blocking semaphore before acquiring an URB. In order to fix the bug, this patch changes the calls copyarea, fillrect and imageblit to offload USB work to a workqueue. A side effect of this patch is 3x improvement in console scrolling speed because the device doesn't have to be updated after each copyarea call. Signed-off-by: Mikulas Patocka Cc: Bernie Thompson Cc: Ladislav Michl Cc: Signed-off-by: Bartlomiej Zolnierkiewicz Signed-off-by: Greg Kroah-Hartman

udlfb: delete the unused parameter for dlfb_handle_damage

2019-05-25T16:16:33Z

commit bd86b6c5c60711dbd4fa21bdb497a188ecb6cf63 upstream. Remove the unused parameter "data" and unused variable "ret". Signed-off-by: Mikulas Patocka Cc: Bernie Thompson Cc: Ladislav Michl Cc: Signed-off-by: Bartlomiej Zolnierkiewicz Signed-off-by: Greg Kroah-Hartman

udlfb: fix some inconsistent NULL checking

2018-12-20T18:13:07Z

In the current kernel, then kzalloc() can't fail for small allocations, but if it did fail then we would have a NULL dereference in the error handling. Also in dlfb_usb_disconnect() if "info" were NULL then it would cause an Oops inside the unregister_framebuffer() function but it can't be NULL so let's remove that check. Fixes: 68a958a915ca ("udlfb: handle unplug properly") Signed-off-by: Dan Carpenter Cc: Bernie Thompson Cc: Mikulas Patocka Cc: Alexey Khoroshilov Cc: Colin Ian King Cc: Wen Yang [b.zolnierkie: added "Fixes:" tag] Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: handle unplug properly

2018-10-08T10:57:34Z

The udlfb driver maintained an open count and cleaned up itself when the count reached zero. But the console is also counted in the reference count - so, if the user unplugged the device, the open count would not drop to zero and the driver stayed loaded with console attached. If the user re-plugged the adapter, it would create a device /dev/fb1, show green screen and the access to the console would be lost. The framebuffer subsystem has reference counting on its own - in order to fix the unplug bug, we rely the framebuffer reference counting. When the user unplugs the adapter, we call unregister_framebuffer unconditionally. unregister_framebuffer will unbind the console, wait until all users stop using the framebuffer and then call the fb_destroy method. The fb_destroy cleans up the USB driver. This patch makes the following changes: * Drop dlfb->kref and rely on implicit framebuffer reference counting instead. * dlfb_usb_disconnect calls unregister_framebuffer, the rest of driver cleanup is done in the function dlfb_ops_destroy. dlfb_ops_destroy will be called by the framebuffer subsystem when no processes have the framebuffer open or mapped. * We don't use workqueue during initialization, but initialize directly from dlfb_usb_probe. The workqueue could race with dlfb_usb_disconnect and this racing would produce various kinds of memory corruption. * We use usb_get_dev and usb_put_dev to make sure that the USB subsystem doesn't free the device under us. Signed-off-by: Mikulas Patocka cc: Dave Airlie Cc: Bernie Thompson , Cc: Ladislav Michl Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: use spin_lock_irq instead of spin_lock_irqsave

2018-07-25T13:41:57Z

spin_lock_irqsave and spin_unlock_irqrestore is inteded to be called from a context where it is unknown if interrupts are enabled or disabled (such as interrupt handlers). From a process context, we should call spin_lock_irq and spin_unlock_irq, that avoids the costly pushf and popf instructions. Signed-off-by: Mikulas Patocka Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: avoid prefetch

2018-07-25T13:41:57Z

Modern processors can detect linear memory accesses and prefetch data automatically, so there's no need to use prefetch. Signed-off-by: Mikulas Patocka Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: optimization - test the backing buffer

2018-07-25T13:41:56Z

Currently, the udlfb driver only tests for identical bytes at the beginning or at the end of a page and renders anything between the first and last mismatching pixel. But pages are not the same as lines, so this is quite suboptimal - if there is something modified at the beginning of a page and at the end of a page, the whole page is rendered, even if most of the page is not modified. This patch makes it test for identical pixels at the beginning and end of each rendering command. This patch improves identical byte detection by 41% when playing video in a window. This patch also fixes a possible screen corruption if the user is writing to the framebuffer while dlfb_render_hline is in progress - the pixel data that is copied to the backbuffer with memcpy may be different from the pixel data that is actually rendered to the hardware (because the content of the framebuffer may change between memcpy and the rendering command). We must make sure that we copy exactly the same pixel as the pixel that is being rendered. Signed-off-by: Mikulas Patocka [b.zolnierkie: fix code indent] Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: allow reallocating the framebuffer

2018-07-25T13:41:56Z

This patch changes udlfb so that it may reallocate the framebuffer when setting higher-resolution mode. If we boot the system without monitor attached, udlfb creates a framebuffer with the size 800x600. This patch makes it possible to select higher videomode with the fbset command when a monitor is attached. Note that there is no reliable way to prevent the system from touching the old framebuffer, so we must not free it. We add it to the list dlfb->deferred_free and free it when the driver is unloaded. Signed-off-by: Mikulas Patocka [b.zolnierkie: sparse fixes] Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: set line_length in dlfb_ops_set_par

2018-07-25T13:41:56Z

Set the variable "line_length" in the function dlfb_ops_set_par. Without this, we get garbage if we select different videomode with fbset. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org Signed-off-by: Bartlomiej Zolnierkiewicz