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

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Message-ID: <4373351e-6dfe-428f-8253-dcc6a1374335@ti.com>
Date: Thu, 15 May 2025 12:03:31 +0530
From: MD Danish Anwar <danishanwar@...com>
To: Vladimir Oltean <vladimir.oltean@....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

Hi Vladimir

On 06/05/25 7:47 pm, Vladimir Oltean wrote:
> 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.

I wasn't aware of this. I will check if I have the setup and try to test
it before posting future revisions.

-- 
Thanks and Regards,
Danish