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

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Message-ID: <77bad70c-49f5-e70c-1fd6-929a394f9cbe@cogentembedded.com>
Date:   Fri, 27 Jan 2017 21:11:35 +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 09:07 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.
>
> Ok, lets leave it and MEMS.
>
>>>>> +	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...
>
> Sure.
>
>> [...]
>>>>> 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.
>
> Ok, I will make it so.

    Your variant is probably even better! :-)
    I'm not sure how good gcc is at merging the similar code paths, 
simplifying its work seems worth it to me. The less repetitive code, the better.

MBR, Sergei