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Date: Fri, 14 Apr 2023 01:01:49 +0000
From: "Song, Yoong Siang" <yoong.siang.song@...el.com>
To: "Keller, Jacob E" <jacob.e.keller@...el.com>,
Stanislav Fomichev <sdf@...gle.com>
CC: Giuseppe Cavallaro <peppe.cavallaro@...com>,
Alexandre Torgue <alexandre.torgue@...s.st.com>,
Jose Abreu <joabreu@...opsys.com>,
"David S . Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
"Jakub Kicinski" <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Maxime Coquelin <mcoquelin.stm32@...il.com>,
Alexei Starovoitov <ast@...nel.org>,
"Daniel Borkmann" <daniel@...earbox.net>,
Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
Alexander Duyck <alexanderduyck@...com>,
"Ong, Boon Leong" <boon.leong.ong@...el.com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-stm32@...md-mailman.stormreply.com"
<linux-stm32@...md-mailman.stormreply.com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"bpf@...r.kernel.org" <bpf@...r.kernel.org>,
"xdp-hints@...-project.net" <xdp-hints@...-project.net>
Subject: RE: [PATCH net-next v3 3/4] net: stmmac: add Rx HWTS metadata to XDP
receive pkt
On Friday, April 14, 2023 12:47 AM, Keller, Jacob E <jacob.e.keller@...el.com> wrote:
>On 4/12/2023 6:39 PM, Song, Yoong Siang wrote:
>> On Thursday, April 13, 2023 5:46 AM, Stanislav Fomichev <sdf@...gle.com>
>wrote:
>>> On Wed, Apr 12, 2023 at 1:56 PM Jacob Keller <jacob.e.keller@...el.com>
>wrote:
>>>>
>>>>
>>>>
>>>> On 4/12/2023 10:00 AM, Stanislav Fomichev wrote:
>>>>> On 04/12, Song Yoong Siang wrote:
>>>>>> Add receive hardware timestamp metadata support via kfunc to XDP
>>>>>> receive packets.
>>>>>>
>>>>>> Suggested-by: Stanislav Fomichev <sdf@...gle.com>
>>>>>> Signed-off-by: Song Yoong Siang <yoong.siang.song@...el.com>
>>>>>> ---
>>>>>> drivers/net/ethernet/stmicro/stmmac/stmmac.h | 3 +++
>>>>>> .../net/ethernet/stmicro/stmmac/stmmac_main.c | 26
>>>>>> ++++++++++++++++++-
>>>>>> 2 files changed, 28 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
>>>>>> b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
>>>>>> index ac8ccf851708..826ac0ec88c6 100644
>>>>>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
>>>>>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
>>>>>> @@ -94,6 +94,9 @@ struct stmmac_rx_buffer {
>>>>>>
>>>>>> struct stmmac_xdp_buff {
>>>>>> struct xdp_buff xdp;
>>>>>> + struct stmmac_priv *priv;
>>>>>> + struct dma_desc *p;
>>>>>> + struct dma_desc *np;
>>>>>> };
>>>>>>
>>>>>> struct stmmac_rx_queue {
>>>>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>>>>>> b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>>>>>> index f7bbdf04d20c..ed660927b628 100644
>>>>>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>>>>>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>>>>>> @@ -5315,10 +5315,15 @@ static int stmmac_rx(struct stmmac_priv
>>>>>> *priv, int limit, u32 queue)
>>>>>>
>>>>>> xdp_init_buff(&ctx.xdp, buf_sz, &rx_q->xdp_rxq);
>>>>>> xdp_prepare_buff(&ctx.xdp, page_address(buf->page),
>>>>>> - buf->page_offset, buf1_len, false);
>>>>>> + buf->page_offset, buf1_len,
>>>>>> + true);
>>>>>>
>>>>>> pre_len = ctx.xdp.data_end - ctx.xdp.data_hard_start -
>>>>>> buf->page_offset;
>>>>>> +
>>>>>> + ctx.priv = priv;
>>>>>> + ctx.p = p;
>>>>>> + ctx.np = np;
>>>>>> +
>>>>>> skb = stmmac_xdp_run_prog(priv, &ctx.xdp);
>>>>>> /* Due xdp_adjust_tail: DMA sync for_device
>>>>>> * cover max len CPU touch @@ -7071,6
>>>>>> +7076,23 @@ void stmmac_fpe_handshake(struct stmmac_priv *priv,
>bool enable)
>>>>>> }
>>>>>> }
>>>>>>
>>>>>> +static int stmmac_xdp_rx_timestamp(const struct xdp_md *_ctx, u64
>>>>>> +*timestamp) {
>>>>>> + const struct stmmac_xdp_buff *ctx = (void *)_ctx;
>>>>>> +
>>>>>> + *timestamp = 0;
>>>>>> + stmmac_get_rx_hwtstamp(ctx->priv, ctx->p, ctx->np,
>>>>>> + timestamp);
>>>>>> +
>>>>>
>>>>> [..]
>>>>>
>>>>>> + if (*timestamp)
>>>>>
>>>>> Nit: does it make sense to change stmmac_get_rx_hwtstamp to return
>>>>> bool to indicate success/failure? Then you can do:
>>>>>
>>>>> if (!stmmac_get_rx_hwtstamp())
>>>>> reutrn -ENODATA;
>>>>
>>>> I would make it return the -ENODATA directly since typically bool
>>>> true/false functions have names like "stmmac_has_rx_hwtstamp" or
>>>> similar name that infers you're answering a true/false question.
>>>>
>>>> That might also let you avoid zeroing the timestamp value first?
>>>
>>> SGTM!
>>
>> stmmac_get_rx_hwtstamp() is used in other places where return value is
>> not needed. Additional if statement checking on return value will add
>> cost, but ignoring return value will hit "unused result" warning.
>>
>
>Isn't unused return values only checked if the function is annotated as
>"__must_check"?
I see. Dint aware that. Thanks for your info.
>
>> I think it will be more make sense if I directly retrieve the
>> timestamp value in stmmac_xdp_rx_timestamp(), instead of reuse
>stmmac_get_rx_hwtstamp().
>>
>
>That makes sense too, the XDP flow is a bit special cased relative to the other
>ones.
Yes, agree.
>
>> Let me send out v4 for review.
>>
>> Thanks & Regards
>> Siang
>>
>>>
>>>> Thanks,
>>>> Jake
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