Hi Nicolas,
On 9/19/23 22:51, Chautru, Nicolas wrote:
Hi Maxime,
This is neither part of 3GPP per se, nor specific to VRB device. Let me provide
more context.
The SRS processing chain
(https://doc.dpdk.org/guides/prog_guide/bbdev.html#bbdev-fft-operation)
includes a pointwise multiplication by time window.
The generic API include some control of these windowing function but still the
actual shape need to be programmed onto any device (ie. rectangular, taped,
sinc, different width or offset, any abritraty shape defined as an array of
scalars). These degrees of liberties cannot be exposed through a generic API
(information is multi-kB, ie the data itself) and can be user specific
(external to the HW IP itself or outside of Intel control).
Thanks for the explanations. I also did my homework as my FFT knowledge
was buried quite deep in my memory. :)
So this is a vendor-specific way to express generic paramaters.
Regarding VRB device, is this table per device or per VF?
Could it be configured by the application directly, or has it to be done
through the PF?
As an illustration for VRB device pf_bb_config provides to user an option to include such
windowing data as an input ("FFT LUT bin file"), but more generally at platform
level for any bb device this big Look-Up Table or big array can be configured on the host
during platform initialization for a given deployment or vendor.
What is required here is for the user application to have knowledge of what
version of such array is being used on the given platform, as this information
would be relevant to processing done outside of bbdev (notably for noise
estimate). Through that mechanism, the user can now map through that API which
possible file was being used, and act accordingly.
The content itself is not specified, for VRB we just use the md5sum of that
binary file (which is just a big array of int16 for point wise multiplication)
so that this can be used to share knowledge between initialized platform
configuration and at run-time user application assumption.
It is also important to under that the user/vendor may use any array or shape
(based on their algorithm) regardless of Intel or IP, and still be able to
share information mapping between what is configured on the platform (multiple
versions possible) and what the application enumerates.
I can add more details in the documentation indeed but above should arguably
make sense. The name FFT_version naming may be quite vague, this is more
related to the FFT pointwise windowing array variant assumed on the platform. I
did not want to impose for it to be an md5sum necessarily, hence the vagueness,
as it could be any hash shared between the device programming and the user
application related to the semi-static FFT processing programming.
Let me know if unclear or if any other thought,
I think this is clear now to me.
In my opinion, this is not good to have this part of the BBDEV API, as
every vendor will have their own way to represent this.
Other alternative is to have a vendor specific API. This is far from
ideal and should be avoided as much as possible, but in this case the
application has to know anyways which device it is driving. It would be
at least clear the field has to be interpreted in a vendor-specific way.
@Hemant, I would be interested in your opinion. (I don't know if NXP has
or plans to have FFT accelerator IP)
Regards,
Maxime
Thanks
Nic
-----Original Message-----
From: Maxime Coquelin <maxime.coque...@redhat.com>
Sent: Tuesday, September 19, 2023 2:56 AM
To: Chautru, Nicolas <nicolas.chau...@intel.com>; dev@dpdk.org
Cc: hemant.agra...@nxp.com; david.march...@redhat.com; Vargas, Hernan
<hernan.var...@intel.com>
Subject: Re: [PATCH v1 1/7] bbdev: add FFT version member in driver info
On 9/19/23 03:21, Nicolas Chautru wrote:
This can be used to distinguish different version of the flexible
pointwise windowing applied to the FFT and expose this to the
application.
Does this version relates to a standard, or is this specific to the
implementation of your VRB devices?
Signed-off-by: Nicolas Chautru <nicolas.chau...@intel.com>
---
lib/bbdev/rte_bbdev.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/lib/bbdev/rte_bbdev.h b/lib/bbdev/rte_bbdev.h index
a5bcc09f10..d6e54ee9a4 100644
--- a/lib/bbdev/rte_bbdev.h
+++ b/lib/bbdev/rte_bbdev.h
@@ -349,6 +349,8 @@ struct rte_bbdev_driver_info {
const struct rte_bbdev_op_cap *capabilities;
/** Device cpu_flag requirements */
const enum rte_cpu_flag_t *cpu_flag_reqs;
+ /** Versioning number for the FFT operation type. */
+ uint16_t fft_version;
};
/** Macro used at end of bbdev PMD list */
