Messages in this thread |  | | Date | Sat, 18 Jan 2025 11:01:22 +0100 | | From | Oleksij Rempel <> | | Subject | Re: [PATCH net-next v1 7/7] net: usb: lan78xx: Enable EEE support with phylink integration |
| |
On Sat, Jan 18, 2025 at 09:04:07AM +0000, Russell King (Oracle) wrote: > On Sat, Jan 18, 2025 at 08:22:15AM +0100, Oleksij Rempel wrote: > > On Fri, Jan 17, 2025 at 04:23:52PM +0000, Russell King (Oracle) wrote: > > > I'm unsure about many DSA drivers. mt753x: > > > > > > u32 set, mask = LPI_THRESH_MASK | LPI_MODE_EN; > > > > > > if (e->tx_lpi_timer > 0xFFF) > > > return -EINVAL; > > > > > > set = LPI_THRESH_SET(e->tx_lpi_timer); > > > if (!e->tx_lpi_enabled) > > > /* Force LPI Mode without a delay */ > > > set |= LPI_MODE_EN; > > > mt7530_rmw(priv, MT753X_PMEEECR_P(port), mask, set); > > > > > > Why force LPI *without* a delay if tx_lpi_enabled is false? This > > > seems to go against the documented API: > > > > > > * @tx_lpi_enabled: Whether the interface should assert its tx lpi, given > > > * that eee was negotiated. > > > > According to MT7531 manual, I would say, the code is not correct: > > https://repo.librerouter.org/misc/lr2/MT7531_switch_Reference_Manual_for_Development_Board.pdf > > > > The LPI_MODE_EN_Px bit has following meaning: > > > > When there is no packet to be transmitted, and the idle time is greater > > than P2_LPI_THRESHOLD, the TXMAC will automatically enter LPI (Low > > Power Idle) mode and send EEE LPI frame to the link partner. > > 0: LPI mode depends on the P2_LPI_THRESHOLD. > > 1: Let the system enter the LPI mode immediately and send EEE LPI frame > > to the link partner. > > Okay, so LPI_MODE_EN_Px causes it to disregard the LPI timer, and enter > LPI mode immediately. Thus, the code should never set LPI_MODE_EN_Px. > > > This chip seems to not have support for tx_lpi_enabled != eee_enabled > > configuration. > > Sorry, I don't see your reasoning there - and I think your > interpretation is different from the documentation (which is > the whole point of having a generic implementation in phylib > to avoid these kinds of different interpretation.) > > * @eee_enabled: EEE configured mode (enabled/disabled). > * @tx_lpi_enabled: Whether the interface should assert its tx lpi, given > * that eee was negotiated. > > eee on|off > Enables/disables the device support of EEE. > > tx-lpi on|off > Determines whether the device should assert its Tx LPI. > > The way phylib interprets eee_enabled is whether EEE is advertised > to the remote device or not. If EEE is not advertised, then EEE is > not negotiated, and thus EEE will not become active. If EEE is not > active, then LPI must not be asserted. tx_lpi_enabled defines whether, > given that EEE has been negotiated, whether LPI should be signalled > after the LPI timer has expired. > > phylib deals with all this logic, and its all encoded into the > phydev->enable_tx_lpi flag to give consistency of implementation. > > Thus, phydev->enable_tx_lpi is only true when eee_enabled && eee > negotiated at the specified speed && tx_lpi_enabled. In that state, > LPI is expected to be signalled after the LPI timer has expired.
I mean, the configuration where EEE can be enabled and in active state, but TX LPI is disabled: eee_enabled = true; eee_active = true; enable_tx_lpi = false. UAPI allows this configuration and it seems to work for 100Mbit/s. Atheros documentation call it asymmetric EEE operation - where each link partner enters LPI mode independently. In comparison, the same documentation calls 1000Mbit EEE mode, symmetric operation - where both link partner must enter the LPI mode simulatneously.
-- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
|  |