[PATCH 00/13] mvneta Buffer Management and enhancements

Marcin Wojtas mw at semihalf.com
Mon Nov 30 11:53:44 PST 2015

Hi Gregory,

2015-11-30 18:16 GMT+01:00 Gregory CLEMENT <gregory.clement at free-electrons.com>:
> Hi Marcin,
>  On dim., nov. 22 2015, Marcin Wojtas <mw at semihalf.com> wrote:
>> Hi,
>> Hereby I submit a patchset that introduces various fixes and support
>> for new features and enhancements to the mvneta driver:
>> 1. First three patches are minimal fixes, stable-CC'ed.
>> 2. Suspend to ram ('s2ram') support. Due to some stability problems
>> Thomas Petazzoni's patches did not get merged yet, but I used them for
>> verification. Contrary to wfi mode ('standby' - linux does not
>> differentiate between them, so same routines are used) all registers'
>> contents are lost due to power down, so the configuration has to be
>> fully reconstructed during resume.
>> 3. Optimisations - concatenating TX descriptors' flush, basing on
>> xmit_more support and combined approach for finalizing egress processing.
>> Thanks to HR timer buffers can be released with small latency, which is
>> good for low transfer and small queues. Along with the timer, coalescing
>> irqs are used, whose threshold could be increased back to 15.
>> 4. Buffer manager (BM) support with two preparatory commits. As it is a
>> separate block, common for all network ports, a new driver is introduced,
>> which configures it and exposes API to the main network driver. It is
>> throughly described in binding documentation and commit log. Please note,
>> that enabling per-port BM usage is done using phandle and the data passed
>> in mvneta_bm_probe. It is designed for usage of on-demand device probe
>> and dev_set/get_drvdata, however it's awaiting merge to linux-next.
>> Therefore, deferring probe is not used - if something goes wrong (same
>> in case of errors during changing MTU or suspend/resume cycle) mvneta
>> driver falls back to software buffer management and works in a regular way.
>> Known issues:
>> - problems with obtaining all mapped buffers from internal SRAM, when
>> destroying the buffer pointer pool
>> - problems with unmapping chunk of SRAM during driver removal
>> Above do not have an impact on the operation, as they are called during
>> driver removal or in error path.
>> 5. Enable BM on Armada XP and 38X development boards - those ones and
>> A370 I could check on my own. In all cases they survived night-long
>> linerate iperf. Also tests were performed with A388 SoC working as a
>> network bridge between two packet generators. They showed increase of
>> maximum processed 64B packets by ~20k (~555k packets with BM enabled
>> vs ~535 packets without BM). Also when pushing 1500B-packets with a
>> line rate achieved, CPU load decreased from around 25% without BM vs
>> 18-20% with BM.
> I was trying to test the BM part of tour series on the Armada XP GP
> board. However it failed very quickly during the pool allocation. After
> a first debug I found that the size of the cs used in the
> mvebu_mbus_dram_info struct was 0. I have applied your series on a
> v4.4-rc1 kernel. At this stage I don't know if it is a regression in the
> mbus driver, a misconfiguration on my side or something else.
> Does it ring a bell for you?

Frankly, I'm a bit surprised, I've never seen such problems on any of
the boards (AXP-GP/DB, A38X-DB/GP/AP). Did mvebu_mbus_dram_win_info
function exit with an error? Can you please apply below diff:
And send me a full log beginning from u-boot?

> How do you test test it exactly?
> Especially on which kernel and with which U-Boot?

I've just re-built the patchset I sent, which is on top of 4.4-rc1.

I use AXP-GP, 78460 @ 1600MHz, 2GB DRAM, and everything works fine. My
u-boot version: v2011.12 2014_T2.0_eng_dropv2.

Best regards,

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