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

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Message-ID: <OS0PR01MB59228540B0F69FA3FE13501886FF9@OS0PR01MB5922.jpnprd01.prod.outlook.com>
Date:   Wed, 18 Aug 2021 10:23:40 +0000
From:   Biju Das <biju.das.jz@...renesas.com>
To:     Sergey Shtylyov <s.shtylyov@....ru>,
        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

Hi Sergei,

> -----Original Message-----
> 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.

Sure. Will do.

Cheers,
Biju