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Date:   Mon, 31 May 2021 22:09:17 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Huazhong Tan <tanhuazhong@huawei.com>
Cc:     <davem@davemloft.net>, <netdev@vger.kernel.org>,
        <salil.mehta@huawei.com>, <yisen.zhuang@huawei.com>,
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        <akiyano@amazon.com>, <thomas.lendacky@amd.com>,
        <irusskikh@marvell.com>, <michael.chan@broadcom.com>,
        <edwin.peer@broadcom.com>, <rohitm@chelsio.com>,
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        <ioana.ciornei@nxp.com>, <vladimir.oltean@nxp.com>,
        <sgoutham@marvell.com>, <sbhatta@marvell.com>, <saeedm@nvidia.com>,
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        <merez@codeaurora.org>, <kvalo@codeaurora.org>,
        <linux-wireless@vger.kernel.org>
Subject: Re: [RFC V2 net-next 1/3] ethtool: extend coalesce setting uAPI
 with CQE mode
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On Mon, 31 May 2021 09:24:01 +0800 Huazhong Tan wrote:
> >> @@ -975,6 +977,8 @@ Request contents:
> >>     ``ETHTOOL_A_COALESCE_TX_USECS_HIGH``         u32     delay (us), h=
igh Tx
> >>     ``ETHTOOL_A_COALESCE_TX_MAX_FRAMES_HIGH``    u32     max packets, =
high Tx
> >>     ``ETHTOOL_A_COALESCE_RATE_SAMPLE_INTERVAL``  u32     rate sampling=
 interval
> >> +  ``ETHTOOL_A_COALESCE_USE_CQE_TX``	       bool    timer reset in CQE=
, Tx
> >> +  ``ETHTOOL_A_COALESCE_USE_CQE_RX``	       bool    timer reset in CQE=
, Rx
> >>     =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D  =3D=3D=3D=
=3D=3D=3D  =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D
> >>  =20
> >>   Request is rejected if it attributes declared as unsupported by driv=
er (i.e. =20
> > Did you provide the theory of operation for CQE vs EQE mode somewhere,
> > as I requested? =20
>=20
>=20
> the definition of enum dim_cq_period_mode in include/linux/dim.h has
>=20
> below comment:
>=20
> /**
>  =C2=A0* enum dim_cq_period_mode - Modes for CQ period count
>  =C2=A0*
>  =C2=A0* @DIM_CQ_PERIOD_MODE_START_FROM_EQE: Start counting from EQE
>  =C2=A0* @DIM_CQ_PERIOD_MODE_START_FROM_CQE: Start counting from CQE (imp=
lies=20
> timer reset)
>  =C2=A0* @DIM_CQ_PERIOD_NUM_MODES: Number of modes
>  =C2=A0*/
>=20
>=20
> is this comment suitable? and add reference in=20
> Documentation/networking/ethtool-netlink.rst to
>=20
> the comment in dim.h.

DIM is kernel internals we need user facing, meaningful documentation.
I'm not 100% clea on what the exact difference is.

If the difference is whether timer is restarted on new packet arrival
or not - why mention CQE at all and not just call the configuration
knob "restart timer on new packet arrival"?