linux-kernel - Re: [PATCH v2 1/2] net: phy: realtek: Add rtl8211e rx/tx delays config

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Date:   Sat, 27 Apr 2019 12:20:23 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Serge Semin <Sergey.Semin@...latforms.ru>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] net: phy: realtek: Add rtl8211e rx/tx delays
 config



On 4/27/2019 12:44 AM, Serge Semin wrote:
> On Fri, Apr 26, 2019 at 08:11:50PM -0700, Florian Fainelli wrote:
>>
>>
>> On 4/26/2019 4:45 PM, Serge Semin wrote:
>>> On Fri, Apr 26, 2019 at 11:40:50PM +0200, Andrew Lunn wrote:
>>>> On Sat, Apr 27, 2019 at 12:21:11AM +0300, Serge Semin wrote:
>>>>> There are two chip pins named TXDLY and RXDLY which actually adds the 2ns
>>>>> delays to TXC and RXC for TXD/RXD latching. Alas this is the only
>>>>> documented info regarding the RGMII timing control configurations the PHY
>>>>> provides. It turns out the same settings can be setup via MDIO registers
>>>>> hidden in the extension pages layout. Particularly the extension page 0xa4
>>>>> provides a register 0x1c, which bits 1 and 2 control the described delays.
>>>>> They are used to implement the "rgmii-{id,rxid,txid}" phy-mode.
>>>>>
>>>>> The hidden RGMII configs register utilization was found in the rtl8211e
>>>>> U-boot driver:
>>>>> https://elixir.bootlin.com/u-boot/v2019.01/source/drivers/net/phy/realtek.c#L99
>>>>>
>>>>> There is also a freebsd-folks discussion regarding this register:
>>>>> https://reviews.freebsd.org/D13591
>>>>>
>>>>> It confirms that the register bits field must control the so called
>>>>> configuration pins described in the table 12-13 of the official PHY
>>>>> datasheet:
>>>>> 8:6 = PHY Address
>>>>> 5:4 = Auto-Negotiation
>>>>> 3 = Interface Mode Select
>>>>> 2 = RX Delay
>>>>> 1 = TX Delay
>>>>> 0 = SELRGV
>>>>>
>>>>> Signed-off-by: Serge Semin <fancer.lancer@...il.com>
>>>>
>>>>
>>>> Hi Serge
>>>>
>>>> Next time please include a patch 0 containing a cover note explaining
>>>> the who series.
>>>>
>>>
>>> Sure as long as the patchset gets to be much bigger than two small
>>> patches with an obvious reason to be merged.
>>
>> netdev likes to have a cover letter for patch count >= 1, probably
>> something to be added to netdev-FAQ.rst.
>> -- 
>> Florian
> 
> Hello Florian
> Really, even with count = 1? So just one patch with cover-letter? Doesn't it
> seem redundant since at least a single patch can be thoroughly described in
> it' commit message?

I was off by one, it's for count > 1 that a cover letter is usually
requested.
-- 
Florian