With the above patch, I still have the screen freeze but without Kernel oops.

I will compile and my own Linux Kernel 4.15 (18.04 LTS) for Ubuntu 20.04 (soon LTS) as
Intel Graphics i915 is unusable on my Dell XPS 13 connected to external
screen and XFCE4

 i915 0000:00:02.0: GPU HANG: ecode 9:1:0x00000000, hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 [drm:gen8_reset_engines [i915]] *ERROR* rcs0 reset request timed out: {request: 00000001, RESET_CTL: 00000001}
 i915 0000:00:02.0: Resetting chip for hang on rcs0
 [drm:gen8_reset_engines [i915]] *ERROR* rcs0 reset request timed out: {request: 00000001, RESET_CTL: 00000001}
 [drm:gen8_reset_engines [i915]] *ERROR* rcs0 reset request timed out: {request: 00000001, RESET_CTL: 00000001}
 Asynchronous wait on fence i915:xfwm4[1901]:57922 timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 Asynchronous wait on fence i915:xfwm4[1901]:57922 timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 ...
 i915 0000:00:02.0: GPU recovery timed out, cancelling all in-flight rendering.
 i915 0000:00:02.0: Resetting chip for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 Asynchronous wait on fence i915:xfwm4[1901]:57926 timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 Asynchronous wait on fence i915:xfwm4[1901]:57926 timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 ...
 i915 0000:00:02.0: GPU recovery timed out, cancelling all in-flight rendering.
 i915 0000:00:02.0: Resetting chip for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 [drm:gen8_reset_engines [i915]] *ERROR* rcs0 reset request timed out: {request: 00000001, RESET_CTL: 00000001}
 i915 0000:00:02.0: Resetting chip for hang on rcs0
 [drm:gen8_reset_engines [i915]] *ERROR* rcs0 reset request timed out: {request: 00000001, RESET_CTL: 00000001}
 [drm:gen8_reset_engines [i915]] *ERROR* rcs0 reset request timed out: {request: 00000001, RESET_CTL: 00000001}
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 Asynchronous wait on fence i915:xfwm4[1901]:5792a timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 Asynchronous wait on fence i915:xfwm4[1901]:5792a timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 ...
 i915 0000:00:02.0: GPU recovery timed out, cancelling all in-flight rendering.
 i915 0000:00:02.0: Resetting chip for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 ...
 Asynchronous wait on fence i915:xfwm4[1901]:5792e timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 Asynchronous wait on fence i915:xfwm4[1901]:5792e timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 ...
 i915 0000:00:02.0: GPU recovery timed out, cancelling all in-flight rendering.
 i915 0000:00:02.0: Resetting chip for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for stuck wait on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 Asynchronous wait on fence i915:xfwm4[1901]:57932 timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 Asynchronous wait on fence i915:xfwm4[1901]:57932 timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 ...
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 i915 0000:00:02.0: GPU recovery timed out, cancelling all in-flight rendering.
 i915 0000:00:02.0: Resetting chip for hang on rcs0
 i915 0000:00:02.0: GPU recovery timed out, cancelling all in-flight rendering.
 i915 0000:00:02.0: Resetting chip for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 Asynchronous wait on fence i915:xfwm4[1901]:57936 timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 Asynchronous wait on fence i915:xfwm4[1901]:57936 timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 ...
 i915 0000:00:02.0: GPU recovery timed out, cancelling all in-flight rendering.
 i915 0000:00:02.0: Resetting chip for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 Asynchronous wait on fence i915:xfwm4[1901]:57938 timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 Asynchronous wait on fence i915:xfwm4[1901]:57938 timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 ...
 i915 0000:00:02.0: GPU recovery timed out, cancelling all in-flight rendering.
 i915 0000:00:02.0: Resetting chip for hang on rcs0
 ...
 Asynchronous wait on fence i915:xfwm4[1901]:5793a timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 Asynchronous wait on fence i915:xfwm4[1901]:5793a timed out (hint:intel_atomic_commit_ready+0x0/0x54 [i915])
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 i915 0000:00:02.0: Resetting rcs0 for hang on rcs0
 ...