Error using discrete Radeon graphics

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I am using Dell Inspiron 15 and have problems getting radeon drivers working on Fedora 23 (I will consider upgrading to F24 as soon as it is out)

Here is the relevant info about the PCI port :

*-pci:2
     description: PCI bridge
     product: 8 Series PCI Express Root Port 5
     vendor: Intel Corporation
     physical id: 1c.4
     bus info: pci@0000:00:1c.4
     version: e4
     width: 32 bits
     clock: 33MHz
     capabilities: pci pciexpress msi pm normal_decode bus_master cap_list
     configuration: driver=pcieport
     resources: irq:44 ioport:3000(size=4096) memory:c0500000-c05fffff ioport:a0000000(size=268435456)
   *-generic
        description: Unassigned class
        product: Illegal Vendor ID
        vendor: Illegal Vendor ID
        physical id: 0
        bus info: pci@0000:03:00.0
        version: ff
        width: 32 bits
        clock: 66MHz
        capabilities: bus_master vga_palette cap_list rom
        configuration: driver=radeon latency=255 maxlatency=255 mingnt=255
        resources: irq:49 memory:a0000000-afffffff memory:c0500000-c053ffff ioport:3000(size=256) memory:c0540000-c055ffff

I tried to run glmark2 tool using DRI_PRIME=1 variable set and ended up with the following error :

radeon: Failed to allocate virtual address for buffer:
radeon:    size      : 65536 bytes
radeon:    alignment : 4096 bytes
radeon:    domains   : 4
radeon:    va        : 0x0000000000800000
radeon: Failed to deallocate virtual address for buffer:
radeon:    size      : 65536 bytes
radeon:    va        : 0x0000000000800000
radeon: Failed to allocate virtual address for buffer:
radeon:    size      : 65536 bytes
radeon:    alignment : 4096 bytes
radeon:    domains   : 4
radeon:    va        : 0x0000000000800000
radeon: Failed to deallocate virtual address for buffer:
radeon:    size      : 65536 bytes
radeon:    va        : 0x0000000000800000
radeonsi: Failed to create a context.
radeon: Failed to allocate virtual address for buffer:
radeon:    size      : 65536 bytes
radeon:    alignment : 4096 bytes
radeon:    domains   : 4
radeon:    va        : 0x0000000000800000
radeon: Failed to deallocate virtual address for buffer:
radeon:    size      : 65536 bytes
radeon:    va        : 0x0000000000800000
radeon: Failed to allocate virtual address for buffer:
radeon:    size      : 65536 bytes
radeon:    alignment : 4096 bytes
radeon:    domains   : 4
radeon:    va        : 0x0000000000800000
radeon: Failed to deallocate virtual address for buffer:
radeon:    size      : 65536 bytes
radeon:    va        : 0x0000000000800000
radeonsi: Failed to create a context.
X Error of failed request:  BadValue (integer parameter out of range for operation)
Major opcode of failed request:  154 (GLX)
Minor opcode of failed request:  24 (X_GLXCreateNewContext)
Value in failed request:  0x0
Serial number of failed request:  35
Current serial number in output stream:  36

Relevant part of lspci | grep radeon :

03:00.0 Display controller: Advanced Micro Devices, Inc. [AMD/ATI] Sun XT [Radeon HD 8670A/8670M/8690M / R5 M330]

As of now, I did not install any drivers. Should I install any specific driver to get it working or is it already pre-installed? Thanks in advance.