linux-kernel - Re: [PATCH net-next 1/2] net: ethernet: ti: am65-cpsw: update pri_thread

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Message-ID: <35a2550e-a422-4938-af3c-a1fb4682ac56@ti.com>
Date: Wed, 6 Nov 2024 10:52:55 +0530
From: Siddharth Vadapalli <s-vadapalli@...com>
To: Roger Quadros <rogerq@...nel.org>
CC: Siddharth Vadapalli <s-vadapalli@...com>,
        Andrew Lunn
	<andrew+netdev@...n.ch>,
        "David S. Miller" <davem@...emloft.net>,
        Eric
 Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni
	<pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
        <linux-omap@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <srk@...com>,
        Pekka Varis <p-varis@...com>
Subject: Re: [PATCH net-next 1/2] net: ethernet: ti: am65-cpsw: update
 pri_thread_map as per IEEE802.1Q-2004

On Tue, Nov 05, 2024 at 04:18:10PM +0200, Roger Quadros wrote:

Hello Roger,

> IEEE802.1Q-2004 superseeds IEEE802.1D-2004. Now Priority Code Point (PCP)

nitpick: s/superseeds/supersedes

Also, according to:
https://standards.ieee.org/ieee/802.1D/3387/
IEEE 802.1D-2004 is superseded by 802.1Q-2014, so:
s/IEEE802.1Q-2004/IEEE802.1Q-2014/g

> 2 is no longer at a lower priority than PCP 0. PCP 1 (Background) is still
> at a lower priority than PCP 0 (Best Effort).
> 
> Reference:
> IEEE802.1Q-2004, Standard for Local and metropolitan area networks
>   Table G-2 - Traffic type acronyms
>   Table G-3 - Defining traffic types

In IEEE802.1Q-2014, the tables are:
Table I-2—Traffic type acronyms
Table I-3—Defining traffic types

> 
> Signed-off-by: Roger Quadros <rogerq@...nel.org>
> ---
>  drivers/net/ethernet/ti/cpsw_ale.c | 25 ++++++++++++++-----------
>  1 file changed, 14 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ti/cpsw_ale.c b/drivers/net/ethernet/ti/cpsw_ale.c
> index 8d02d2b21429..7dadd95cadc5 100644
> --- a/drivers/net/ethernet/ti/cpsw_ale.c
> +++ b/drivers/net/ethernet/ti/cpsw_ale.c
> @@ -1692,26 +1692,29 @@ static void cpsw_ale_policer_reset(struct cpsw_ale *ale)
>  void cpsw_ale_classifier_setup_default(struct cpsw_ale *ale, int num_rx_ch)
>  {
>  	int pri, idx;
> -	/* IEEE802.1D-2004, Standard for Local and metropolitan area networks
> +	/* IEEE802.1Q-2004, Standard for Local and metropolitan area networks
>  	 *    Table G-2 - Traffic type acronyms
>  	 *    Table G-3 - Defining traffic types
> -	 * User priority values 1 and 2 effectively communicate a lower
> -	 * priority than 0. In the below table 0 is assigned to higher priority
> -	 * thread than 1 and 2 wherever possible.
> +	 * Also: https://en.wikipedia.org/wiki/IEEE_P802.1p#Priority_levels

Since links might change, it might be better to drop this and quote section
I.4 Traffic types and priority values of IEEE802.1Q-2014 which states:

"0 is thus used both for default priority and for Best Effort, and
Background is associated with a priority value of 1. This means that the
value 1 effectively communicates a lower priority than 0."

> +	 * Priority Code Point (PCP) value 1 (Background) communicates a lower
> +	 * priority than 0 (Best Effort). In the below table PCP 0 is assigned
> +	 * to a higher priority thread than PCP 1 wherever possible.
>  	 * The below table maps which thread the user priority needs to be
>  	 * sent to for a given number of threads (RX channels). Upper threads
>  	 * have higher priority.
>  	 * e.g. if number of threads is 8 then user priority 0 will map to
> -	 * pri_thread_map[8-1][0] i.e. thread 2
> +	 * pri_thread_map[8-1][0] i.e. thread 1
>  	 */
> -	int pri_thread_map[8][8] = {	{ 0, 0, 0, 0, 0, 0, 0, 0, },
> +
> +	int pri_thread_map[8][8] = {   /* BK,BE,EE,CA,VI,VO,IC,NC */
> +					{ 0, 0, 0, 0, 0, 0, 0, 0, },
>  					{ 0, 0, 0, 0, 1, 1, 1, 1, },
>  					{ 0, 0, 0, 0, 1, 1, 2, 2, },
> -					{ 1, 0, 0, 1, 2, 2, 3, 3, },
> -					{ 1, 0, 0, 1, 2, 3, 4, 4, },
> -					{ 1, 0, 0, 2, 3, 4, 5, 5, },
> -					{ 1, 0, 0, 2, 3, 4, 5, 6, },
> -					{ 2, 0, 1, 3, 4, 5, 6, 7, } };
> +					{ 0, 0, 1, 1, 2, 2, 3, 3, },
> +					{ 0, 0, 1, 1, 2, 2, 3, 4, },
> +					{ 1, 0, 2, 2, 3, 3, 4, 5, },
> +					{ 1, 0, 2, 3, 4, 4, 5, 6, },
> +					{ 1, 0, 2, 3, 4, 5, 6, 7 } };
>  
>  	cpsw_ale_policer_reset(ale);

Regards,
Siddharth.