The wings of a computer engineer
The wings of a computer engineer

Personal blog for Timothy D Meadows II

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Ubuntu on Inspiron 11 3147 (2 in 1) and dw_dmac

Timothy D Meadows IITimothy D Meadows II

On August 24th, 2014 i purchased a Dell Inspiron 11 3147 2 in 1 Laptop & Tablet combo (The 4GB Quad-Core edition). The system came pre-installed with Windows 8.1 which personally i hate.

The first thing i did when i got it was install Ubuntu 12.04. This was the officially supported Ubuntu version according to Dell. The only real complaint i had about 12.04 was the lack of real touch screen support. The touch screen was just treated as another mouse with no gestures. Not really useful short of “clicking” on something with your finger from time to time.

After some research I realized that Ubuntu 14 was out and it seemed to have full support for touch screens including gestures. While not supported officially by Dell. Driver support was there for everything including the sensors (Accelerometer, Temp, GPS, Compass) and even Intel had Video drivers for 14.04 out.

I installed Ubuntu 14.04 and despite my high hopes had terrible trouble. The USB rail would not function at all (would not even power devices). The touch screen did not work at all (not even as a mouse). The system would also hang on reboot / shutdown.

After a lot of debugging and searching of the Ubuntu developer list I found out that the dwdmac driver had problems in Ubuntu 13+ on Inspiron machines that we’re using it. The dwdmac driver is actually the Synopsys DesignWare DMA Controller driver. Blacklisting the driver was the best solution i could find.

sudo nano /etc/modprobe.d/blacklist.conf

Then at the bottom of the file add this line.

blacklist dw_dmac

Save the file. Then reboot the system. It still hangs but if you press f6 right as you see the purple screen showing the Ubuntu splash screen it should remove the splash screen allowing you to see when the system is indeed ready to be turned off.

After rebooting all hardware related problems (including reboot, suspend, resume and shutdown) should now be resolved. The usb rail should now function and the touch screen gestures should now work.

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