netdev - RE: [PATCH net-next v2 7/8] ravb: Add internal delay hw feature to struct ravb_hw

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Date:   Wed, 4 Aug 2021 10:08:15 +0000
From:   Biju Das <biju.das.jz@...renesas.com>
To:     Sergey Shtylyov <s.shtylyov@....ru>,
        Sergei Shtylyov <sergei.shtylyov@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
CC:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Sergey Shtylyov <s.shtylyov@...russia.ru>,
        Adam Ford <aford173@...il.com>, Andrew Lunn <andrew@...n.ch>,
        Yuusuke Ashizuka <ashiduka@...itsu.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: RE: [PATCH net-next v2 7/8] ravb: Add internal delay hw feature to
 struct ravb_hw_info

Hi Sergei,

Thanks for feedback

> Subject: Re: [PATCH net-next v2 7/8] ravb: Add internal delay hw feature
> to struct ravb_hw_info
> 
> On 04.08.2021 8:13, Biju Das wrote:
> > Hi Sergei,
> >
> > Thanks for the feedback
> >
> >> Subject: Re: [PATCH net-next v2 7/8] ravb: Add internal delay hw
> >> feature to struct ravb_hw_info
> >>
> >> On 8/2/21 1:26 PM, Biju Das wrote:
> >>
> >>> R-Car Gen3 supports TX and RX clock internal delay modes, whereas
> >>> R-Car
> >>> Gen2 and RZ/G2L do not support it.
> >>> Add an internal_delay hw feature bit to struct ravb_hw_info to
> >>> enable this only for R-Car Gen3.
> >>>
> >>> Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
> >>> Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> >>> ---
> >>> v2:
> >>>   * Incorporated Andrew and Sergei's review comments for making it
> >> smaller patch
> >>>     and provided detailed description.
> >>> ---
> >>>   drivers/net/ethernet/renesas/ravb.h      | 3 +++
> >>>   drivers/net/ethernet/renesas/ravb_main.c | 6 ++++--
> >>>   2 files changed, 7 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/net/ethernet/renesas/ravb.h
> >>> b/drivers/net/ethernet/renesas/ravb.h
> >>> index 3df813b2e253..0d640dbe1eed 100644
> >>> --- a/drivers/net/ethernet/renesas/ravb.h
> >>> +++ b/drivers/net/ethernet/renesas/ravb.h
> >>> @@ -998,6 +998,9 @@ struct ravb_hw_info {
> >>>   	int num_tx_desc;
> >>>   	int stats_len;
> >>>   	size_t skb_sz;
> >>> +
> >>> +	/* hardware features */
> >>> +	unsigned internal_delay:1;	/* RAVB has internal delays */
> >>
> >>     Oops, missed it initially:
> >>     RAVB? That's not a device name, according to the manuals. It
> >> seems to be the driver's name.
> >
> > OK. will change it to AVB-DMAC has internal delays.
> 
>     Please don't -- E-MAC has them, not AVB-DMAC.

By looking at HW manual for R-Car AVB-DMAC (APSR register, offset:-0x08C) has TDM and RDM registers for Setting internal delay mode which can give TX clock delay up to 2.0ns and RX Clock delay 2.8ns.

Please correct me, if this is not the case.

Regards,
Biju



> 
> > Cheers,
> > Biju
> 
> NBR, Sergei