netdev - Re: [PATCH net-next v2 1/8] ravb: Add struct ravb_hw

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Message-ID: <dcbf2171-080c-d743-6aeb-6936b498d1fd@omp.ru>
Date:   Wed, 18 Aug 2021 13:11:44 +0300
From:   Sergey Shtylyov <s.shtylyov@....ru>
To:     Biju Das <biju.das.jz@...renesas.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Sergey Shtylyov <s.shtylyov@...russia.ru>
CC:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Sergei Shtylyov <sergei.shtylyov@...il.com>,
        Adam Ford <aford173@...il.com>, Andrew Lunn <andrew@...n.ch>,
        Yuusuke Ashizuka <ashiduka@...itsu.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        netdev <netdev@...r.kernel.org>,
        Linux-Renesas <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 1/8] ravb: Add struct ravb_hw_info to driver
 data

Hello!

On 18.08.2021 9:29, Biju Das wrote:

[...]
>>>>>>> -----Original Message-----
>>>>>>> On Mon, Aug 2, 2021 at 12:27 PM Biju Das
>>>>>>> <biju.das.jz@...renesas.com>
>>>>>>> wrote:
>>>>>>>> The DMAC and EMAC blocks of Gigabit Ethernet IP found on RZ/G2L
>>>>>>>> SoC are similar to the R-Car Ethernet AVB IP. With a few changes
>>>>>>>> in the driver we can support both IPs.
>>>>>>>>
>>>>>>>> Currently a runtime decision based on the chip type is used to
>>>>>>>> distinguish the HW differences between the SoC families.
>>>>>>>>
>>>>>>>> The number of TX descriptors for R-Car Gen3 is 1 whereas on R-Car
>>>>>>>> Gen2 and RZ/G2L it is 2. For cases like this it is better to
>>>>>>>> select the number of TX descriptors by using a structure with a
>>>>>>>> value, rather than a runtime decision based on the chip type.
>>>>>>>>
>>>>>>>> This patch adds the num_tx_desc variable to struct ravb_hw_info
>>>>>>>> and also replaces the driver data chip type with struct
>>>>>>>> ravb_hw_info by moving chip type to it.
>>>>>>>>
>>>>>>>> Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
>>>>>>>> Reviewed-by: Lad Prabhakar
>>>>>>>> <prabhakar.mahadev-lad.rj@...renesas.com>
>>>>>>>
>>>>>>> Thanks for your patch!
>>>>>>>
>>>>>>>> --- a/drivers/net/ethernet/renesas/ravb.h
>>>>>>>> +++ b/drivers/net/ethernet/renesas/ravb.h
>>>>>>>> @@ -988,6 +988,11 @@ enum ravb_chip_id {
>>>>>>>>          RCAR_GEN3,
>>>>>>>>   };
>>>>>>>>
>>>>>>>> +struct ravb_hw_info {
>>>>>>>> +       enum ravb_chip_id chip_id;
>>>>>>>> +       int num_tx_desc;
>>>>>>>
>>>>>>> Why not "unsigned int"? ...
>>>>>>> This comment applies to a few more subsequent patches.
>>>>>>
>>>>>> To avoid signed and unsigned comparison warnings.
>>>>>>
>>>>>>>
>>>>>>>> +};
>>>>>>>> +
>>>>>>>>   struct ravb_private {
>>>>>>>>          struct net_device *ndev;
>>>>>>>>          struct platform_device *pdev; @@ -1040,6 +1045,8 @@
>>>>>>>> struct ravb_private {
>>>>>>>>          unsigned txcidm:1;              /* TX Clock Internal Delay
>>>>> Mode
>>>>>>> */
>>>>>>>>          unsigned rgmii_override:1;      /* Deprecated rgmii-*id
>>>>> behavior
>>>>>>> */
>>>>>>>>          int num_tx_desc;                /* TX descriptors per
>>>> packet
>>>>> */
>>>>>>>
>>>>>>> ... oh, here's the original culprit.
>>>>>>
>>>>>> Exactly, this the reason.
>>>>>>
>>>>>> Do you want me to change this into unsigned int? Please let me know.
>>>>>
>>>>> Up to you (or the maintainer? ;-)
>>>>>
>>>>> For new fields (in the other patches), I would use unsigned for all
>>>>> unsigned values.  Signed values have more pitfalls related to
>>>>> undefined behavior.
>>>>
>>>> Sergei, What is your thoughts here? Please let me know.
>>>
>>> Here is my plan.
>>>
>>> I will split this patch into two as Andrew suggested and
>>
>>     If you mran changing the ravb_private::num_tx_desc to *unsigned*, it'll
>> be a good cleanup. What's would be the 2nd part tho?
> 
> OK in that case, I will split this patch into 3.
> 
> First patch for adding struct ravb_hw_info to driver data and replace
> driver data chip type with struct ravb_hw_info

    Couldn't this be a 2nd patch?..

> Second patch for changing ravb_private::num_tx_desc from int to unsigned int.

    ... and this one the 1st?

> Third patch for adding aligned_tx to struct ravb_hw_info.
> 
> Regards,
> Biju

MBR, Sergey