drm/i915/skl: Add support to load SKL CSR firmware.

Display Context Save and Restore support is needed for
various SKL Display C states like DC5, DC6.

This implementation is added based on first version of DMC CSR program
that we received from h/w team.

Here we are using request_firmware based design.
Finally this firmware should end up in linux-firmware tree.

For SKL platform its mandatory to ensure that we load this
csr program before enabling DC states like DC5/DC6.

As CSR program gets reset on various conditions, we should ensure
to load it during boot and in future change to be added to load
this system resume sequence too.

v1: Initial relese as RFC patch

v2: Design change as per Daniel, Damien and Shobit's review comments
request firmware method followed.

v3: Some optimization and functional changes.
Pulled register defines into drivers/gpu/drm/i915/i915_reg.h
Used kmemdup to allocate and duplicate firmware content.
Ensured to free allocated buffer.

v4: Modified as per review comments from Satheesh and Daniel
Removed temporary buffer.
Optimized number of writes by replacing I915_WRITE with I915_WRITE64.

v5:
Modified as per review comemnts from Damien.
- Changed name for functions and firmware.
- Introduced HAS_CSR.
- Reverted back previous change and used csr_buf with u8 size.
- Using cpu_to_be64 for endianness change.

Modified as per review comments from Imre.
- Modified registers and macro names to be a bit closer to bspec terminology
and the existing register naming in the driver.
- Early return for non SKL platforms in intel_load_csr_program function.
- Added locking around CSR program load function as it may be called
concurrently during system/runtime resume.
- Releasing the fw before loading the program for consistency
- Handled error path during f/w load.

v6: Modified as per review comments from Imre.
- Corrected out_freecsr sequence.

v7: Modified as per review comments from Imre.
Fail loading fw if fw->size%8!=0.

v8: Rebase to latest.

v9: Rebase on top of -nightly (Damien)

v10: Enabled support for dmc firmware ver 1.0.
According to ver 1.0 in a single binary package all the firmware's that are
required for different stepping's of the product will be stored. The package
contains the css header, followed by the package header and the actual dmc
firmwares. Package header contains the firmware/stepping mapping table and
the corresponding firmware offsets to the individual binaries, within the
package. Each individual program binary contains the header and the payload
sections whose size is specified in the header section. This changes are done
to extract the specific firmaware from the package. (Animesh)

v11: Modified as per review comemnts from Imre.
- Added code comment from bpec for header structure elements.
- Added __packed to avoid structure padding.
- Added helper functions for stepping and substepping info.
- Added code comment for CSR_MAX_FW_SIZE.
- Disabled BXT firmware loading, will be enabled with dmc 1.0 support.
- Changed skl_stepping_info based on bspec, earlier used from config DB.
- Removed duplicate call of cpu_to_be* from intel_csr_load_program function.
- Used cpu_to_be32 instead of cpu_to_be64 as firmware binary in dword aligned.
- Added sanity check for header length.
- Added sanity check for mmio address got from firmware binary.
- kmalloc done separately for dmc header and dmc firmware. (Animesh)

v12: Modified as per review comemnts from Imre.
- Corrected the typo error in skl stepping info structure.
- Added out-of-bound access for skl_stepping_info.
- Sanity check for mmio address modified.
- Sanity check added for stepping and substeppig.
- Modified the intel_dmc_info structure, cache only the required header info. (Animesh)

v13: clarify firmware load error message.
The reason for a firmware loading failure can be obscure if the driver
is built-in. Provide an explanation to the user about the likely reason for
the failure and how to resolve it. (Imre)

v14: Suggested by Jani.
- fix s/I915/CONFIG_DRM_I915/ typo
- add fw_path to the firmware object instead of using a static ptr (Jani)

v15:
1) Changed the firmware name as dmc_gen9.bin, everytime for a new firmware version a symbolic link
with same name will help not to build kernel again.
2) Changes done as per review comments from Imre.
- Error check removed for intel_csr_ucode_init.
- Moved csr-specific data structure to intel_csr.h and optimization done on structure definition.
- fw->data used directly for parsing the header info & memory allocation
only done separately for payload. (Animesh)

v16:
- No need for out_regs label in i915_driver_load(), so removed it.
- Changed the firmware name as skl_dmc_ver1.bin, followed naming convention <platform>_dmc_<api-version>.bin (Animesh)

Issue: VIZ-2569
Signed-off-by: A.Sunil Kamath <sunil.kamath@intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>