Messages in this thread | | | Date | Wed, 30 Aug 2023 10:13:47 +0200 | From | Lukasz Majewski <> | Subject | Re: [PATCH 2/2] net: dsa: microchip: Provide Module 4 KSZ9477 errata (DS80000754C) |
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Hi Oleksij,
> On Tue, Aug 29, 2023 at 10:23:26PM +0000, Tristram.Ha@microchip.com > wrote: > > > Yes, removing linkmod_and() will not should not help. I said, "The > > > phydev->supported_eee should be cleared." > > > > > > For example like this: > > > --- a/drivers/net/phy/micrel.c > > > +++ b/drivers/net/phy/micrel.c > > > @@ -1400,6 +1400,7 @@ static int ksz9131_config_aneg(struct > > > phy_device *phydev) > > > > > > static int ksz9477_get_features(struct phy_device *phydev) > > > { > > > + __ETHTOOL_DECLARE_LINK_MODE_MASK(zero) = { 0, }; > > > int ret; > > > > > > ret = genphy_read_abilities(phydev); > > > @@ -1413,7 +1414,7 @@ static int ksz9477_get_features(struct > > > phy_device *phydev) > > > * KSZ8563R should have 100BaseTX/Full only. > > > */ > > > linkmode_and(phydev->supported_eee, phydev->supported, > > > - PHY_EEE_CAP1_FEATURES); > > > + zero); > > > > > > return 0; > > > } > > > > > > You will need to clear it only on KSZ9477 variants with this bug. > > > This change is tested and it works on my KSZ9477-EVB. > > > > I think this is best for disabling EEE support. > > I think before some customers asked for Ethtool EEE support not > > because they want to use it but to disable it because of link > > instability. KSZ9893/KSZ9563 switches should have the same problem. > > The EEE problem depends on the link partner. For example my > > laptop does not have problem even though EEE is enabled, although I > > am not sure if EEE is really active. The problem here is just > > using two KSZ9477 switches and programming those PHY setup values > > and enabling EEE will make the link unstable. Management decided > > to disable EEE feature to avoid customer support issues. > > Another issue is EEE should be disabled when using 1588 PTP. > > > > I'd like to share my thoughts on the concerns raised: > > - KSZ9477 & EEE: Disabling EEE for the KSZ9477 makes sense, > especially since the datasheet doesn't list it as supported. >
+1
I will prepare proper patch
> - EEE Support for KSZ9893 & KSZ9563: The datasheets for the KSZ9893 > indicate support for EEE. The erratum recommends making adjustments > to the "transmit Refresh Time for Waketx to meet the IEEE Refresh > Time specification" instead of turning it off completely. The same > applies to KSZ9563. We should consider these adjustments. > > - General Experience with KSZ Chips*: From my experience with these > chips, irrespective of the EEE functionality, only the 1000/full and > 100/full link modes tend to be stable enough. > > - Responsibility to Customers and Certifications: As a part of the > product supply chain, I believe in our commitment to honesty with our > customers. When we select components for end products, we trust their > listed features. For instance, designing for ENERGY STAR > certification requires that all copper-based physical network ports > in an LNE product must be compliant with IEEE 802.3 Clause 78, which > mandates Energy Efficient Ethernet. If Microchip promotes a KSZ* chip > with EEE as a feature, it becomes a cornerstone of the end product. > Negating a key functionality, which was sold and then incorporated > into the product, could risk non-compliance with certification > criteria. > > - Consistency in Product Representation: If the overarching company > decision is to disable the EEE feature for all chips to preempt > potential customer support issues, our product information should > mirror this change. It's crucial that we neither misrepresent nor > over-promise on features. Your deeper insights, given your > involvement with Microchip's strategy, would be most enlightening. >
For the last two - at least the KSZ9477 Errata was clear about the issue. Other (switch IC) vendors have even problems to admit that something is wrong with their silicon design...
> Regards, > Oleksij
Best regards,
Lukasz Majewski
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