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

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Date:   Wed, 18 Aug 2021 06:29:54 +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,

Thanks for the feedback.

> Subject: Re: [PATCH net-next v2 1/8] ravb: Add struct ravb_hw_info to
> driver data
> 
> On 8/17/21 2:24 PM, 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

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

Third patch for adding aligned_tx to struct ravb_hw_info.

Regards,
Biju