linux-kernel - Re: [PATCH net 1/1] net: stmmac: add fsleep() in HW Rx timestamp checking loop

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Date:   Tue, 19 Apr 2022 06:28:53 -0700
From:   Richard Cochran <richardcochran@...il.com>
To:     Tan Tee Min <tee.min.tan@...ux.intel.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Tan Tee Min <tee.min.tan@...el.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S . Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Rayagond Kokatanur <rayagond@...avyalabs.com>,
        netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Voon Wei Feng <weifeng.voon@...el.com>,
        Wong Vee Khee <vee.khee.wong@...el.com>,
        Song Yoong Siang <yoong.siang.song@...el.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>
Subject: Re: [PATCH net 1/1] net: stmmac: add fsleep() in HW Rx timestamp
 checking loop

On Tue, Apr 19, 2022 at 08:52:20AM +0800, Tan Tee Min wrote:

> I agree that the fsleep(1) (=1us) is a big hammer.
> Thus in order to improve this, I’ve figured out a smaller delay
> time that is enough for the context descriptor to be ready which
> is ndelay(500) (=500ns).

Why isn't the context descriptor ready?

I mean, the frame already belongs to the CPU, right?

Thanks,
Richard