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

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Message-ID: <bdfeb1c1-98bf-25ed-a4db-6ca3c5abc099@gmail.com>
Date:   Wed, 4 Aug 2021 13:34:06 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...il.com>
To:     Biju Das <biju.das.jz@...renesas.com>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        "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

On 04.08.2021 13:08, Biju Das wrote:
> 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.

    You're correct indeed -- though being counter-intuitive, APSR belongs to 
the AVB-DMAC block. Sorry about that. :-/

>  Regards,
> Biju

NBR, Sergei