netdev - Re: [PATCH net-next 1/2] ravb: Add tx and rx clock internal delays mode of APSR

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Message-ID: <d1e19006-b57f-9429-1e6e-ff906ced47a0@cogentembedded.com>
Date:   Fri, 27 Jan 2017 19:55:25 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     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,
        Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>
Subject: Re: [PATCH net-next 1/2] ravb: Add tx and rx clock internal delays
 mode of APSR

On 01/27/2017 07:49 PM, Simon Horman wrote:

>>> From: Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>
>>>
>>> This patch enables tx and rx clock internal delay modes (TDM and RDM).
>>>
>>> This is to address a failure in the case of 1Gbps communication using the
>>> by salvator-x board with the KSZ9031RNX phy. This has been reported to
>>> occur with both the r8a7795 (H3) and r8a7796 (M3-W) SoCs.
>>>
>>> With this change APSR internal delay modes are enabled for
>>> "rgmii-id", "rgmii-rxid" and "rgmii-txid" phy modes as follows:
>>>
>>> phy mode   | ASPR delay mode
>>> -----------+----------------
>>> rgmii-id   | TDM and RDM
>>> rgmii-rxid | RDM
>>> rgmii-txid | TDM
>>>
>>> Signed-off-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>
>>> Signed-off-by: Simon Horman <horms+renesas@...ge.net.au>
>>>
>>> ---
>>> v1 [Simon Horman]
>>> - Combined patches
>>> - Reworded changelog
>>>
>>> v0 [Kazuya Mizuguchi]
>>> ---
>>> drivers/net/ethernet/renesas/ravb.h      | 10 ++++++++++
>>> drivers/net/ethernet/renesas/ravb_main.c | 29 +++++++++++++++++++++++++++++
>>> 2 files changed, 39 insertions(+)
>>>
>>> diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
>>> index f1109661a533..d7c91d48cc48 100644
>>> --- a/drivers/net/ethernet/renesas/ravb.h
>>> +++ b/drivers/net/ethernet/renesas/ravb.h
>> [...]
>>> @@ -248,6 +249,15 @@ enum ESR_BIT {
>>> 	ESR_EIL		= 0x00001000,
>>> };
>>>
>>> +/* APSR */
>>> +enum APSR_BIT {
>>> +	APSR_MEMS		= 0x00000002,
>>
>>    Not documented in the revision 0.5 of the gen3 manual...
>
> It is in version 0.53 of the documentation but I think it can be dropped
> from this patch as its unused.

    No need to drop, let it be. :-)

>>> +	APSR_CMSW		= 0x00000010,
>
> I think the above can also be dropped as it is unused.

    No need.

>>> +	APSR_DM			= 0x00006000,
>>
>>    ... and neither this field. Are these documented in the latter revs?
>
> This one is not. I can ask Mizuguchi-san to confirm it exists (with himself).

    The whole patch depends on it! If it's not documented, I'd like a comment 
added, like I did for the other undocumented things in this driver...

[...]
>>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>>> index 89ac1e3f6175..9fb4c04c5885 100644
>>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>>> @@ -1904,6 +1904,29 @@ static void ravb_set_config_mode(struct net_device *ndev)
>>> 	}
>>> }
>>>
>>> +static void ravb_set_delay_mode(struct net_device *ndev)
>>> +{
>>> +	struct ravb_private *priv = netdev_priv(ndev);
>>> +
>>> +	if (priv->chip_id != RCAR_GEN2) {
>>> +		switch (priv->phy_interface) {
>>> +		case PHY_INTERFACE_MODE_RGMII_ID:
>>> +			ravb_modify(ndev, APSR, APSR_DM, APSR_DM_RDM |
>>> +				   APSR_DM_TDM);
>>> +			break;
>>> +		case PHY_INTERFACE_MODE_RGMII_RXID:
>>> +			ravb_modify(ndev, APSR, APSR_DM, APSR_DM_RDM);
>>> +			break;
>>> +		case PHY_INTERFACE_MODE_RGMII_TXID:
>>> +			ravb_modify(ndev, APSR, APSR_DM, APSR_DM_TDM);
>>> +			break;
>>> +		default:
>>> +			ravb_modify(ndev, APSR, APSR_DM, 0);
>>> +			break;
>>> +		}
>>
>>    How about doing ravb_modify() only once?
>
> Something like this?
>
> 		int set = 0;
>
> 		if (priv->phy_interface == PHY_INTERFACE_MODE_RGMII_ID ||
> 		    priv->phy_interface == PHY_INTERFACE_MODE_RGMII_RXID)
> 		    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;
>
> 		ravb_modify(ndev, APSR, APSR_DM, set);
>
> I don't really see any advantage to it but I can change things around
> however you like.

    I didn't mean to replace *switch*, actually -- just to move ravb_modify() 
out of it.

MBR, Sergei