Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752202AbaBKRok (ORCPT ); Tue, 11 Feb 2014 12:44:40 -0500 Received: from mail-pa0-f46.google.com ([209.85.220.46]:33407 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751358AbaBKRoi convert rfc822-to-8bit (ORCPT ); Tue, 11 Feb 2014 12:44:38 -0500 MIME-Version: 1.0 In-Reply-To: <52F9E8E6.1090006@keymile.com> References: <7510122.cayuQ6qt8r@wuerfel> <52F8FB03.6040606@keymile.com> <29007785.iYrLORbRAN@lenovo> <52F9E8E6.1090006@keymile.com> From: Florian Fainelli Date: Tue, 11 Feb 2014 09:43:57 -0800 Message-ID: Subject: Re: [PATCH V3] net/dt: Add support for overriding phy configuration from device tree To: Gerlando Falauto Cc: Matthew Garrett , netdev , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Kishon Vijay Abraham I Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Gerlando, 2014-02-11 1:09 GMT-08:00 Gerlando Falauto : > Hi Florian, > > first of all, thank you for your answer. > > > On 02/10/2014 06:09 PM, Florian Fainelli wrote: >> >> Hi Gerlando, >> >> Le lundi 10 février 2014, 17:14:59 Gerlando Falauto a écrit : >>> >>> Hi, >>> >>> I'm currently trying to fix an issue for which this patch provides a >>> partial solution, so apologies in advance for jumping into the >>> discussion for my own purposes... >>> >>> On 02/04/2014 09:39 PM, Florian Fainelli wrote:> 2014-01-17 Matthew >>> >>> Garrett : >>> >> Some hardware may be broken in interesting and board-specific ways, >>> such >>> >> that various bits of functionality don't work. This patch provides a >>> >> mechanism for overriding mii registers during init based on the >>> >>> contents of >>> >>> >> the device tree data, allowing board-specific fixups without having >>> to >>> >> pollute generic code. >>> > >>> > It would be good to explain exactly how your hardware is broken >>> > exactly. I really do not think that such a fine-grained setting where >>> > you could disable, e.g: 100BaseT_Full, but allow 100BaseT_Half to >>> > remain usable makes that much sense. In general, Gigabit might be >>> > badly broken, but 100 and 10Mbits/sec should work fine. How about the >>> > MASTER-SLAVE bit, is overriding it really required? >>> > >>> > Is not a PHY fixup registered for a specific OUI the solution you are >>> > looking for? I am also concerned that this creates PHY >>> troubleshooting >>> > issues much harder to debug than before as we may have no idea about >>> > how much information has been put in Device Tree to override that. >>> > >>> > Finally, how about making this more general just like the BCM87xx PHY >>> > driver, which is supplied value/reg pairs directly? There are 16 >>> > common MII registers, and 16 others for vendor specific registers, >>> > this is just covering for about 2% of the possible changes. >>> >>> Good point. That would easily help me with my current issue, which >>> requires autoneg to be disabled to begin with (by clearing BMCR_ANENABLE >>> from register 0). >> >> >> Is there a point in time (e.g: after some specific initial configuration >> has >> been made) where BMCR_ANENABLE can be used? > > > What do you mean? In my case, for some HW-related reason (due to the PHY > counterpart I guess) autoneg needs to be disabled. > This is currently done by the bootloader code (which clears the bit). > What I'm looking for is some way for the kernel to either reinforce this > setting, or just take that into account and skip autoneg. > On top of that, there's a HW errata about that particular PHY, which > requires certain operations to be performed on the PHY as a workaround *WHEN > AUTONEG IS DISABLED*. That I'd implement on a PHY-specif driver. Ok. > > >>> This would not however fix it entirely (I tried a quick hardwired >>> implementation), as the whole PHY machinery would not take that into >>> account and would re-enable autoneg anyway. >>> I also tried changing the patch so that phydev->support gets updated >> >> >> There are multiple things that you could try doing here: >> >> - override the PHY state machine in your read_status callback to make sure >> that you always set phydev->autoneg set to AUTONEG_ENABLE > > > [you mean AUTONEG_DISABLE, right?] Right, I fat fingered here. > Uhm, but I don't want to implement a driver for that PHY that always > disables autoneg. I only want to disable autoneg for that particular board. > I figure I might register a fixup for that board, but that kindof makes > everything more complicated and less clear. Plus, what should be the > criterion to determine whether we're running on that particular hardware? of_machine_is_compatible() plus reading the specific PHY OUI should provide you with with an unique machine + PHY tuple. If your machine name is too generic. > > >> - clear the SUPPORTED_Autoneg bits from phydev->supported right after PHY >> registration and before the call to phy_start() > > > I actually tried clearing it by tweaking the patch on this thread, but the > end result is that it does not produce any effect (see further comments > below). Only thing that seems to play a role here is explictly setting > phydev->autoneg = AUTONEG_DISABLE. > > >> - set the PHY_HAS_MAGICANEG bit in your PHY driver flag > > > Again, this seems to play no role whatsoever here: > > } else if (0 == phydev->link_timeout--) { > needs_aneg = 1; > /* If we have the magic_aneg bit, > * we try again */ > if (phydev->drv->flags & PHY_HAS_MAGICANEG) > break; > } > break; > case PHY_NOLINK: > > This code might have made sense when it was written in 2006 -- back then, > the break statement was skipping some fallback code. But now it seems to do > nothing. > > >> >>> >>> (instead of phydev->advertising): >>> >> + if (!of_property_read_u32(np, override->prop, &tmp)) >>> { >>> >> + if (tmp) { >>> >> + *val |= override->value; >>> >> + phydev->advertising |= >>> >>> override->supported; >>> >>> >> + } else { >>> >> + phydev->advertising &= >>> >>> ~(override->supported); >>> >>> >> + } >>> >> + >>> >> + *mask |= override->value; >>> >>> What I find weird is that the only way phydev->autoneg could ever be set >>> to disabled is from here (phy.c): >>> >>> static void phy_sanitize_settings(struct phy_device *phydev) >>> { >>> u32 features = phydev->supported; >>> int idx; >>> >>> /* Sanitize settings based on PHY capabilities */ >>> if ((features & SUPPORTED_Autoneg) == 0) >>> phydev->autoneg = AUTONEG_DISABLE; >>> >>> which is in turn only called when phydev->autoneg is set to >>> AUTONEG_DISABLE to begin with: >>> >>> int phy_start_aneg(struct phy_device *phydev) >>> { >>> int err; >>> >>> mutex_lock(&phydev->lock); >>> >>> if (AUTONEG_DISABLE == phydev->autoneg) >>> phy_sanitize_settings(phydev); >>> >>> So could someone please help me figure out what I'm missing here? >> >> >> At first glance it looks like the PHY driver should be reading the phydev- >>> >>> autoneg value when the PHY driver config_aneg() callback is called to be >> >> allowed to set the forced speed and settings. >> >> The way phy_sanitize_settings() is coded does not make it return a mask of >> features, but only the forced supported speed and duplex. Then when the >> link >> is forced but we are having some issues getting a link status, libphy >> tries >> lower speeds and this function is used again to provide the next >> speed/duplex >> pair to try. >> > > What I was trying to say is that phy_sanitize_settings() is only called when > phydev->autoneg == AUTONEG_DISABLE, and in turn it's the only generic > function setting phydev->autoneg = AUTONEG_DISABLE. > So perhaps the condition should read: > > - if (AUTONEG_DISABLE == phydev->autoneg) > + if ((features & SUPPORTED_Autoneg) == 0) > phy_sanitize_settings(phydev); > > Or else, some other parts of the generic code should take care of setting it > to AUTONEG_DISABLE, depending on whether the feature is supported or not. > What I found weird is explicitly setting a value (phydev->autoneg = > AUTONEG_DISABLE), from a static function which is only called when that > condition is already true. I do not think that this change is correct either, let me cook a patch for you to allow disabling autoneg from the start. > > BTW, I feel like disabling autoneg from the start has never been a use case > before, am I right? Not really no, and that is because most hardware does not need quirks to work correctly. > > Thanks! > Gerlando -- Florian -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/