Re: [PATCH net-next v2] net: stmmac: Caclucate CDC error only once

On Mon, Nov 22, 2021 at 12:19 PM Kurt Kanzenbach [off-list ref] wrote:

The clock domain crossing error (CDC) is calculated at every fetch of Tx or Rx
timestamps. It includes a division. Especially on arm32 based systems it is
expensive. It also requires two conditionals in the hotpath.

Add a compensation value cache to struct plat_stmmacenet_data and subtract it
unconditionally in the RX/TX functions which spares the conditionals.

The value is initialized to 0 and if supported calculated in the PTP
initialization code.

Suggested-by: Thomas Gleixner <redacted>
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
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Nit: "Caclucate" in the subject

-- 
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