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

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Date:   Wed, 4 Aug 2021 22:27:21 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...il.com>
To:     Biju Das <biju.das.jz@...renesas.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 1/8] ravb: Add struct ravb_hw_info to driver
 data

On 8/3/21 8:57 AM, Biju Das wrote:

>> Subject: Re: [PATCH net-next v2 1/8] ravb: Add struct ravb_hw_info to
>> driver data
>>
>> On 8/2/21 1:26 PM, Biju Das 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>
>>> ---
>>> v2:
>>>  * Incorporated Andrew and Sergei's review comments for making it
>> smaller patch
>>>    and provided detailed description.
>>> ---
>>>  drivers/net/ethernet/renesas/ravb.h      |  7 +++++
>>>  drivers/net/ethernet/renesas/ravb_main.c | 38
>>> +++++++++++++++---------
>>>  2 files changed, 31 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/renesas/ravb.h
>>> b/drivers/net/ethernet/renesas/ravb.h
>>> index 80e62ca2e3d3..cfb972c05b34 100644
>>> --- 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;

   How about leaving that field in the *struct* ravb_private? And adding the following instead:

	unsigned unaligned_tx: 1;

>>    I think this is rather the driver's choice, than the h/w feature...
>> Perhaps a rename would help with that? :-)
> 
> It is consistent with current naming convention used by the driver. NUM_TX_DESC macro is replaced by num_tx_desc and  the below run time decision based on chip type for H/W configuration for Gen2/Gen3 is replaced by info->num_tx_desc.
> 
> priv->num_tx_desc = chip_id == RCAR_GEN2 ? NUM_TX_DESC_GEN2 : NUM_TX_DESC_GEN3;

   .. and then:

	priv->num_tx_desc =  info->unaligned_tx ? NUM_TX_DESC_GEN2 : NUM_TX_DESC_GEN3;

> Please let me know, if I am missing anything,
> 
> Previously there is a suggestion to change the generic struct ravb_driver_data (which holds driver differences and HW features) with struct ravb_hw_info.

    Well, my plan was to place all the hardware features supported into the *struct* ravb_hw_info and leave all
the driver's software data in the *struct* ravb_private.

> Regards,
> Biju
[...]

MBR, Sergei