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

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Message-ID: <20220420125439.GA1401@hoboy.vegasvil.org>
Date:   Wed, 20 Apr 2022 05:54:39 -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 Wed, Apr 20, 2022 at 01:15:08PM +0800, Tan Tee Min wrote:
> No. The context descriptor (frame) is possibly still owned by the
> DMA controller in this situation.

So that is a problem.  The solution is to postpone this logic until
the driver owns the buffer.  Doesn't the HW offer some means of
notification, like an interrupt for example?

Thanks,
Richard