[PATCH v1 00/10] baseband/acc200

[Maxime Coquelin]

On 9/14/22 12:35, Thomas Monjalon wrote:
> 06/09/2022 14:51, Tom Rix:
>> On 9/1/22 1:34 PM, Chautru, Nicolas wrote:
>>> From: Tom Rix <trix at redhat.com>
>>>> On 8/31/22 6:26 PM, Chautru, Nicolas wrote:
>>>>> From: Tom Rix <trix at redhat.com>
>>>>>> On 8/31/22 3:37 PM, Chautru, Nicolas wrote:
>>>>>>>>>>> Comparing ACC200 & ACC100 header files, I understand ACC200 is
>>>>>>>>>>> an evolution of the ACC10x family. The FEC bits are really
>>>>>>>>>>> close,
>>>>>>>>>>> ACC200 main addition seems to be FFT acceleration which could be
>>>>>>>>>>> handled in ACC10x driver based on device ID.
>>>>>>>>>>>
>>>>>>>>>>> I think both drivers have to be merged in order to avoid code
>>>>>>>>>>> duplication. That's how other families of devices (e.g. i40e)
>>>>>>>>>>> are handled.
>>>>>>>>>> I haven't seen your reply on this point.
>>>>>>>>>> Do you confirm you are working on a single driver for ACC family
>>>>>>>>>> in order to avoid code duplication?
>>>>>>>>>>
>>>>>>>>> The implementation is based on distinct ACC100 and ACC200 drivers.
>>>>>>>>> The 2
>>>>>>>> devices are fundamentally different generation, processes and IP.
>>>>>>>>> MountBryce is an eASIC device over PCIe while ACC200 is an
>>>>>>>>> integrated
>>>>>>>> accelerator on Xeon CPU.
>>>>>>>>> The actual implementation are not the same, underlying IP are all
>>>>>>>>> distinct
>>>>>>>> even if many of the descriptor format have similarities.
>>>>>>>>> The actual capabilities of the acceleration are different and/or new.
>>>>>>>>> The workaround and silicon errata are also different causing
>>>>>>>>> different
>>>>>>>> limitation and implementation in the driver (see the serie with
>>>>>>>> ongoing changes for ACC100 in parallel).
>>>>>>>>> This is fundamentally distinct from ACC101 which was a derivative
>>>>>>>>> product
>>>>>>>> from ACC100 and where it made sense to share implementation
>>>> between
>>>>>>>> ACC100 and ACC101.
>>>>>>>>> So in a nutshell these 2 devices and drivers are 2 different
>>>>>>>>> beasts and the
>>>>>>>> intention is to keep them intentionally separate as in the serie.
>>>>>>>>> Let me know if unclear, thanks!
>>>>>>>> Nic,
>>>>>>>>
>>>>>>>> I used a similarity checker to compare acc100 and acc200
>>>>>>>>
>>>>>>>> https://dickgrune.com/Programs/similarity_tester/
>>>>>>>>
>>>>>>>> l=simum.log
>>>>>>>> if [ -f $l ]; then
>>>>>>>>          rm $l
>>>>>>>> fi
>>>>>>>>
>>>>>>>> sim_c -s -R -o$l -R -p -P -a .
>>>>>>>>
>>>>>>>> There results are
>>>>>>>>
>>>>>>>> ./acc200/acc200_pf_enum.h consists for 100 % of
>>>>>>>> ./acc100/acc100_pf_enum.h material ./acc100/acc100_pf_enum.h
>>>>>>>> consists for 98 % of ./acc200/acc200_pf_enum.h material
>>>>>>>> ./acc100/rte_acc100_pmd.h consists for
>>>>>>>> 98 % of ./acc200/acc200_pmd.h material ./acc200/acc200_vf_enum.h
>>>>>>>> consists for 95 % of ./acc100/acc100_pf_enum.h material
>>>>>>>> ./acc200/acc200_pmd.h consists for 92 % of
>>>>>>>> ./acc100/rte_acc100_pmd.h material ./acc200/rte_acc200_cfg.h
>>>>>>>> consists for 92 % of ./acc100/rte_acc100_cfg.h material
>>>>>>>> ./acc100/rte_acc100_pmd.c consists for 87 % of
>>>>>>>> ./acc200/rte_acc200_pmd.c material ./acc100/acc100_vf_enum.h
>>>>>>>> consists for
>>>>>>>> 80 % of ./acc200/acc200_pf_enum.h material
>>>>>>>> ./acc200/rte_acc200_pmd.c consists for 78 % of
>>>>>>>> ./acc100/rte_acc100_pmd.c material ./acc100/rte_acc100_cfg.h
>>>>>>>> consists for 75 % of ./acc200/rte_acc200_cfg.h material
>>>>>>>>
>>>>>>>> Spot checking the first *pf_enum.h at 100%, these are the devices'
>>>>>>>> registers, they are the same.
>>>>>>>>
>>>>>>>> I raised this similarity issue with 100 vs 101.
>>>>>>>>
>>>>>>>> Having multiple copies is difficult to support and should be avoided.
>>>>>>>>
>>>>>>>> For the end user, they should have to use only one driver.
>>>>>>>>
>>>>>>> There are really different IP and do not have the same interface
>>>>>>> (PCIe/DDR vs
>>>>>> integrated) and there is big serie of changes which are specific to
>>>>>> ACC100 coming in parallel. Any workaround, optimization would be
>>>> different.
>>>>>>> I agree that for the coming serie of integrated accelerator we will
>>>>>>> use a
>>>>>> unified driver approach but for that very case that would be quite
>>>>>> messy to artificially put them within the same PMD.
>>>>>>
>>>>>> How is the IP different when 100% of the registers are the same ?
>>>>>>
>>>>> These are 2 different HW aspects. The base toplevel configuration registers
>>>> are kept similar on purpose but the underlying IP are totally different design
>>>> and implementation.
>>>>> Even the registers have differences but not visible here, the actual RDL file
>>>> would define more specifically these registers bitfields and implementation
>>>> including which ones are not implemented (but that is proprietary
>>>> information), and at bbdev level the interface is not some much register
>>>> based than processing based on data from DMA.
>>>>> Basically even if there was a common driver, all these would be duplicated
>>>> and they are indeed different IP (including different vendors)..
>>>>> But I agree with the general intent and to have a common driver for the
>>>> integrated driver serie (ACC200, ACC300...) now that we are moving away
>>>> from PCIe/DDR lookaside acceleration and eASIC/FPGA implementation
>>>> (ACC100/AC101).
>>>>
>>>> Looking a little deeper, at how the driver is lays out some of its bitfields and
>>>> private data by reviewing the
>>>>
>>>> ./acc200/acc200_pmd.h consists for 92 % of ./acc100/rte_acc100_pmd.h
>>>>
>>>> There are some minor changes to existing reserved bitfields.
>>>> A new structure for fft.
>>>> The acc200_device, the private data for the driver, is an exact copy of
>>>> acc100_device.
>>>>
>>>> acc200_pmd.h is the superset and could be used with little changes as a
>>>> common acc_pmd.h.
>>>> acc200 is doing everything the acc100 did in a very similar if not exact way,
>>>> adding the fft feature.
>>>>
>>>> Can you point to some portion of this patchset that is so unique that it could
>>>> not be abstracted to an if-check or function and so requiring this separate,
>>>> nearly identical driver ?
>>>>
>>> You used a similarity checker really, there are actually way more relevent differences than what you imply here.
>>> With regards to the 2 pf_enum.h file, there are many registers that have same or similar names but have now different values being mapped hence you just cannot use one for the other.
>>> Saying that "./acc200/acc200_pmd.h consists for 92 % of ./acc100/rte_acc100_pmd.h" is just not correct and really irrelevant.
>>> Just do a diff side by side please and check, that should be extremely obvious, that metrics tells more about the similarity checker limitation than anything else.
>>> Even when using a common driver for ACC200/300 they will have distinct register enum files being auto-generated and coming from distinct RDL.
>>> Again just do a diff of these 2 files. I believe you will agree that is not relevant for these files to try to artificially merged these together.
>>>
>>> With regards to the pmd.h, some structure/defines are indeed common and could be moved to a common file (for instance turboencoder and LDPC encoder which are more vanilla and unlikely to change for future product unlike the decoders which have different feature set and behaviour; or some 3GPP constant that can be defined once).
>>> We can definitely change these to put together shared structures/defines, but not intending to try to artificially put things together with spaghetti code.
>>> We would like to keep 3 parallel versions of these PMD for 3 different product lines which are indeed fundamentally different designs (including different workaround required as can be seen on the parallel ACC100 serie under review).
>>> - one version for FPGA implementation (support for N3000, N6000, ...)
>>> - one version for eASIC lookaside card implementation (ACC100, ACC101, ...)
>>> - one version for the integrated Xeon accelerators (ACC200, ACC300, ...)
>>
>> Some suggestions on refactoring,
>>
>> For the registers, have a common file.
>>
>> For the shared functionality, ex/ ldpc encoder, break these out to its
>> own shared file.
>>
>> The public interface, see my earlier comments on the documentation,
>> should be have the same interfaces and the few differences highlighted.
> 
> +1 to have common files, and all in a single directory drivers/baseband/acc100/

Jus to be sure we are aligned, do you mean to have both drivers in the
same directory, which will share some common files? That's the way I
would go.

Thanks,
Maxime