linux-kernel - Re: [PATCH v8 net-next 05/11] net: ethernet: am65-cpsw: cleanup TAPRIO handling

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Date:   Thu, 14 Dec 2023 15:41:31 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Roger Quadros <rogerq@...nel.org>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, shuah@...nel.org, s-vadapalli@...com,
        r-gunasekaran@...com, vigneshr@...com, srk@...com,
        horms@...nel.org, p-varis@...com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 net-next 05/11] net: ethernet: am65-cpsw: cleanup
 TAPRIO handling

On Thu, Dec 14, 2023 at 03:36:57PM +0200, Roger Quadros wrote:
> Actually, this code is already present upstream. I'm only moving it around
> in this patch.
> 
> Based on the error message and looking at am65_cpsw_est_check_scheds() and
> am65_cpsw_est_set_sched_list() which is called later in am65_cpsw_taprio_replace(),
> both of which eventually call am65_est_cmd_ns_to_cnt() which expects valid link_speed,
> my understanding is that the author intended to have a valid link_speed before
> proceeding further.
> 
> Although it seems netif_running() check isn't enough to have valid link_speed
> as the link could still be down even if the netif is brought up.
> 
> Another gap is that in am65_cpsw_est_link_up(), if link was down for more than 1 second
> it just abruptly calls am65_cpsw_taprio_destroy().
> 
> So I think we need to do the following to improve taprio support in this driver:
> 1) accept taprio schedule irrespective of netif/link_speed status
> 2) call pm_runtime_get()/put() before any device access regardless of netif/link_speed state
> 3) on link_up when if have valid link_speed and taprio_schedule, apply it.
> 4) on link_down, destroy the taprio schedule form the controller.
> 
> But my concern is, this is a decent amount of work and I don't want to delay this series.
> My original subject of this patch series was mpqrio/frame-preemption/coalescing. ;)
> 
> Can we please defer taprio enhancement to a separate series? Thanks!

Ok, sounds fair to have some further taprio clean-up scheduled for later.
I would also add taprio_offload_get() to the list of improvements that
could be made.