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

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Date:   Mon, 15 Apr 2019 13:45:52 +0200
From:   Simon Horman <horms@...ge.net.au>
To:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc:     Andrew Lunn <andrew@...n.ch>, 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 07:36:35PM +0300, Sergei Shtylyov wrote:
> 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...

Thanks, how about this?

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 4f648394e645..9618c4881c83 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -1980,8 +1987,12 @@ 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 (!WARN(soc_device_match(ravb_delay_mode_quirk_match),
+			  "phy-mode %s requires TX clock internal delay mode which is not supported by this hardware revision. Please update device tree",
+			  phy_modes(priv->phy_interface)))
+			set |= APSR_DM_TDM;
+	}
 
 	ravb_modify(ndev, APSR, APSR_DM, set);
 }