linux-kernel - Re: [PATCH net-next v10] net: ti: icssg-prueth: add TAPRIO offload support

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Message-ID: <20250506141709.rnhvtoghn2tc47rw@skbuf>
Date: Tue, 6 May 2025 17:17:09 +0300
From: Vladimir Oltean <vladimir.oltean@....com>
To: MD Danish Anwar <danishanwar@...com>
Cc: Meghana Malladi <m-malladi@...com>,
	Vignesh Raghavendra <vigneshr@...com>,
	Simon Horman <horms@...nel.org>,
	Guillaume La Roque <glaroque@...libre.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Roger Quadros <rogerq@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, srk@...com,
	Roger Quadros <rogerq@...com>
Subject: Re: [PATCH net-next v10] net: ti: icssg-prueth: add TAPRIO offload
 support

On Fri, May 02, 2025 at 04:12:35PM +0530, MD Danish Anwar wrote:
> From: Roger Quadros <rogerq@...com>
> 
> The Time-Aware Shaper (TAS) is a key feature of the Enhanced Scheduled
> Traffic (EST) mechanism defined in IEEE 802.1Q-2018. This patch adds TAS
> support for the ICSSG driver by interacting with the ICSSG firmware to
> manage gate control lists, cycle times, and other TAS parameters.
> 
> The firmware maintains active and shadow lists. The driver updates the
> operating list using API `tas_update_oper_list()` which,
> - Updates firmware list pointers via `tas_update_fw_list_pointers`.
> - Writes gate masks, window end times, and clears unused entries in the
>   shadow list.
> - Updates gate close times and Max SDU values for each queue.
> - Triggers list changes using `tas_set_trigger_list_change`, which
>   - Computes cycle count (base-time % cycle-time) and extend (base-time %
>     cycle-time)
>   - Writes cycle time, cycle count, and extend values to firmware memory.
>   - base-time being in past or base-time not being a multiple of
>     cycle-time is taken care by the firmware. Driver just writes these
>     variable for firmware and firmware takes care of the scheduling.
>   - If base-time is not a multiple of cycle-time, the value of extend
>     (base-time % cycle-time) is used by the firmware to extend the last
>     cycle.
>   - Sets `config_change` and `config_pending` flags to notify firmware of
>     the new shadow list and its readiness for activation.
>   - Sends the `ICSSG_EMAC_PORT_TAS_TRIGGER` r30 command to ask firmware to
>     swap active and shadow lists.
> - Waits for the firmware to clear the `config_change` flag before
>   completing the update and returning successfully.
> 
> This implementation ensures seamless TAS functionality by offloading
> scheduling complexities to the firmware.
> 
> Signed-off-by: Roger Quadros <rogerq@...com>
> Signed-off-by: Vignesh Raghavendra <vigneshr@...com>
> Reviewed-by: Simon Horman <horms@...nel.org>
> Signed-off-by: MD Danish Anwar <danishanwar@...com>
> ---

This is not a review comment - just wanted to mention that a week ago,
I've added a selftest for this feature at
tools/testing/selftests/net/forwarding/tc_taprio.sh, and I'm wondering
whether you have the necessary setup to give that a run. That would give
maintainers a bit more confidence when merging, that things work as
expected.