netdev - Re: [PATCH v2 net-next] ravb: Avoid unsupported internal delay mode for R-Car E3/D3

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Message-ID: <a6bd1a3a-0c6f-6d2a-9270-f5819c34d4e7@cogentembedded.com>
Date:   Thu, 11 Apr 2019 19:36:35 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Andrew Lunn <andrew@...n.ch>, Simon Horman <horms@...ge.net.au>
Cc:     David Miller <davem@...emloft.net>,
        Magnus Damm <magnus.damm@...il.com>, netdev@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>
Subject: Re: [PATCH v2 net-next] ravb: Avoid unsupported internal delay mode
 for R-Car E3/D3

On 04/11/2019 04:33 PM, Andrew Lunn wrote:

>>>>>> According to the R-Car Gen3 Hardware Manual Rev 1.50 of Nov 30, 2018, the
>>>>>> TX clock internal delay mode isn't supported on R-Car E3 (r8a77990) or D3
>>>>>> (r8a77995). And by extension it is also not supported by RZ/G2E (r9a774c0).
>>>>>>
>>>>>> This matches all ES versions of the affected SoCs as it is
>>>>>> not clear if this problem will be resolved in newer chips.
>>>>>> This can be revisited, as necessary.
>>>>>>
>>>>>> This patch does not error-out if PHY_INTERFACE_MODE_RGMII_ID or
>>>>>> PHY_INTERFACE_MODE_RGMII_TXID are used on SoCs where TX clock delay
>>>>>> mode is not supported as there is a risk of introducing a regression
>>>>>> when used in conjunction with older DT blobs present in the field.
>>>>>
>>>>> Hi Simon
>>>>>
>>>>> I think it should at least WARN_ON(). Such blobs are broken, even if
>>>>> they do kind of work.
>>>>
>>>>    Good idea! Simon, third time's a charm? :-)
>>>
>>> Sure, can do.
>>
>> How about something like this?
>>
>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>> @@ -1980,8 +1987,14 @@ static void ravb_set_delay_mode(struct net_device *ndev)
>>  		set |= APSR_DM_RDM;
>>  
>>  	if (priv->phy_interface == PHY_INTERFACE_MODE_RGMII_ID ||
>> -	    priv->phy_interface == PHY_INTERFACE_MODE_RGMII_TXID)
>> -		set |= APSR_DM_TDM;
>> +	    priv->phy_interface == PHY_INTERFACE_MODE_RGMII_TXID) {
>> +		if (soc_device_match(ravb_delay_mode_quirk_match))
>> +			dev_warn(ndev->dev.parent,
>> +				 "phy-mode %s requires TX clock internal delay mode which is not supported by this hardwre revision",
>> +				 phy_modes(priv->phy_interface));
> 
> Hi Simon
> 
> The point of the warning is to tell users they should upgrade their DT
> blob to one that is not broken. So i think the message should say
> this. Also, we want users to notice this, which is why i said
> WARN_ON(). Something big so it gets noticed.

   I agree in general but I guess you meant WARN() -- WARN_ON() doesn't take
a string arg...

> 	   Andrew

MBR, Sergei