linux-kernel - Re: [PATCH net-next] tg3: Link IRQs to NAPI instances

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Message-ID: <2ddd0888-abef-4d28-851a-adeaa380641a@amd.com>
Date: Thu, 12 Sep 2024 10:50:56 -0700
From: Brett Creeley <bcreeley@....com>
To: Joe Damato <jdamato@...tly.com>, netdev@...r.kernel.org
Cc: Pavan Chebbi <pavan.chebbi@...adcom.com>,
 Michael Chan <mchan@...adcom.com>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next] tg3: Link IRQs to NAPI instances



On 9/12/2024 8:58 AM, Joe Damato wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> 
> 
> Link IRQs to NAPI instances with netif_napi_set_irq. This information
> can be queried with the netdev-genl API.
> 
> Compare the output of /proc/interrupts for my tg3 device with the output of
> netdev-genl after applying this patch:
> 
> $ cat /proc/interrupts | grep eth0 | cut -f1 --delimiter=':'
>   331
>   332
>   333
>   334
>   335
> 
> $ ./tools/net/ynl/cli.py --spec Documentation/netlink/specs/netdev.yaml \
>                           --dump napi-get --json='{"ifindex": 2}'
> 
> [{'id': 149, 'ifindex': 2, 'irq': 335},
>   {'id': 148, 'ifindex': 2, 'irq': 334},
>   {'id': 147, 'ifindex': 2, 'irq': 333},
>   {'id': 146, 'ifindex': 2, 'irq': 332},
>   {'id': 145, 'ifindex': 2, 'irq': 331}]
> 
> Signed-off-by: Joe Damato <jdamato@...tly.com>
> ---
>   drivers/net/ethernet/broadcom/tg3.c | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
> index 378815917741..c187b13ab3e6 100644
> --- a/drivers/net/ethernet/broadcom/tg3.c
> +++ b/drivers/net/ethernet/broadcom/tg3.c
> @@ -7393,6 +7393,14 @@ static int tg3_poll(struct napi_struct *napi, int budget)
>          return work_done;
>   }
> 
> +static void tg3_napi_set_irq(struct tg3 *tp)
> +{
> +       int i;
> +
> +       for (i = 0; i < tp->irq_cnt; i++)
> +               netif_napi_set_irq(&tp->napi[i].napi, tp->napi[i].irq_vec);
> +}
> +
>   static void tg3_napi_disable(struct tg3 *tp)
>   {
>          int i;
> @@ -11652,7 +11660,7 @@ static int tg3_start(struct tg3 *tp, bool reset_phy, bool test_irq,
>                  goto out_ints_fini;
> 
>          tg3_napi_init(tp);
> -
> +       tg3_napi_set_irq(tp);

I haven't used this API yet, so I was trying to figure out if this is 
the right place to call it. I think it is, but other examples may not 
have put it in the right place.

I think there is a minor bug in fbnic/fbnic_txrx.c. I say this based on 
the following:

fbnic_alloc_napi_vector() {
<snip>
-> netif_napi_set_irq() # napi->irq = irq
-> netif_napi_add()
	-> netif_napi_add_weight() # napi->irq = -1
<snip>
}

Just as an FYI I submitted a patch to fix this just now based on 
reviewing your code:

https://lore.kernel.org/netdev/20240912174922.10550-1-brett.creeley@amd.com/T/#u

LGTM.

Reviewed-by: Brett Creeley <brett.creeley@....com>

>          tg3_napi_enable(tp);
> 
>          for (i = 0; i < tp->irq_cnt; i++) {
> --
> 2.25.1
> 
>