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

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Date:   Thu, 11 Apr 2019 15:33:57 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Simon Horman <horms@...ge.net.au>
Cc:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        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 Thu, Apr 11, 2019 at 11:20:57AM +0200, Simon Horman wrote:
> On Thu, Apr 11, 2019 at 10:40:27AM +0200, Simon Horman wrote:
> > On Wed, Apr 10, 2019 at 08:17:16PM +0300, Sergei Shtylyov wrote:
> > > On 04/10/2019 07:19 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.

	   Andrew