On 9/28/23 18:33, Chautru, Nicolas wrote:
HI Maxime,
-----Original Message-----
From: Maxime Coquelin <maxime.coque...@redhat.com>
Sent: Thursday, September 28, 2023 1:27 AM
To: Chautru, Nicolas <nicolas.chau...@intel.com>; hemant.agra...@nxp.com;
dev@dpdk.org
Cc: david.march...@redhat.com; Vargas, Hernan <hernan.var...@intel.com>
Subject: Re: [PATCH v1 1/7] bbdev: add FFT version member in driver info
Hi Nicolas,
On 9/28/23 01:50, Chautru, Nicolas wrote:
Hi Maxime, Hemant,
I wanted initially to keep it fairly open hence a hash table for the windows
profiles, but it is also possible to expose something more descriptive, that
would work as well actually.
Ie.
+ /** FFT windowing width for 2048 FFT. */
+ uint16_t fft_window_width[RTE_BBDEV_MAX_FFT_WIN];
The provides the width of each windows shape which is enough to
distinguish major variants and to estimate noise factor.
That sounds much better IMHO.
Regarding the array and values sizes:
1. Should it only covers 2048 points FFT? I see some references about
4096 FFT for 5G and satellites communications 2. Is uint16_t enough for all the
usecases?
That is a misunderstanding, probably because I did not include the definition
and value of RTE_BBDEV_MAX_FFT_WIN on the snippet above.
The dimension of the array is purely the number of windows to choose from, ie.
16.
Ok, where is the number of windows made available?
That is NOT an array matching the size of the FFT. In effect that width value
is for the reference for 2048 FFT, but the actual width would be scaled down
when a lower FFT is being set or higher for bigger FFT, so this doesn’t make
assumption on the max FFT size, just a given portion using a reference
resolution for 2048 FFT.
Ok, if you could document this with example that would be great.
Maybe you have some existing links explaining that?
Uint16_t is more than enough, that width cannot be more than 1024 based on
reference above.
Since this array is quite big, could it be exposed to the application via
dedicated
APIs instead of a field? An API to query the length of the array so that the
application can allocate required meory, and an API to copy the data in the
allocated mem?
Maybe overkill, but I feel different FFT size could be supported in the future,
so
that would be both future proof and more memory efficient for apps that
don't need this.
Note above, let me know if unclear.
It is not clear to me how this representation is generic or specific to
your device.
Thanks,
Maxime
Let me know of opinion.
Thanks for suggesting this,
Maxime
Thanks
Nic
-----Original Message-----
From: Maxime Coquelin <maxime.coque...@redhat.com>
Sent: Tuesday, September 26, 2023 3:00 AM
To: Chautru, Nicolas <nicolas.chau...@intel.com>;
hemant.agra...@nxp.com; dev@dpdk.org
Cc: 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 9/22/23 18:41, Chautru, Nicolas wrote:
Hi Maxime,
-----Original Message-----
From: Maxime Coquelin <maxime.coque...@redhat.com>
Sent: Friday, September 22, 2023 1:15 AM
To: Chautru, Nicolas <nicolas.chau...@intel.com>;
hemant.agra...@nxp.com; dev@dpdk.org
Cc: david.march...@redhat.com; Vargas, Hernan
<hernan.var...@intel.com>
Subject: Re: [PATCH v1 1/7] bbdev: add FFT version member in driver
info
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-operat
io
n) 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.
Unsure this is that vendor specific. At least the interface allows
to know a
hash of the table being loaded (which is just pointwise data really,
non- proprietary format). I did not state the content is a simple
md5sum of the bin file being loaded from linux.
Ok, I think it would be better to provide an API to get the table
directly, and have the format being described in the documentation.
With that, we can also provide the hash as you'd like, but the method
to calculate the hash should also be provided. Or the application can
perform the hash itself if it needs it.
The fact that it is several KB is not an issue, as this information
would only be queried once at init time if really needed.
An non-DPDK alternative could be to pass such information to the pod
via the device plugin (as a mounted file for instance, or variable).
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?
This is configured for the device at platform level, ie. through operator.
Common to all application/devices. This captures the windows shape
assumptions.
Thanks for the information!
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)
Yes looking forward to it.
Thanks,
Maxime
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 */
