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

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Date:   Fri, 27 Jan 2017 19:21:14 +0100
From:   Simon Horman <horms@...ge.net.au>
To:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
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 Fri, Jan 27, 2017 at 09:11:35PM +0300, Sergei Shtylyov wrote:
> 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.

Ok, thanks. I'll go with my version.