On 12/19/2019 7:30 AM, Priyanka Jain wrote:
-----Original Message----- From: U-Boot u-boot-bounces@lists.denx.de On Behalf Of Marek Vasut Sent: Wednesday, December 18, 2019 9:47 PM To: joe.hershberger@ni.com Cc: u-boot@lists.denx.de; Tom Rini trini@konsulko.com; Joseph Hershberger joseph.hershberger@ni.com Subject: Re: [U-Boot] [PATCH] net/phy: Fix phy_connect() for phy addr 0
On 12/18/19 5:15 PM, Joe Hershberger wrote:
On Tue, Dec 17, 2019 at 11:55 PM Marek Vasut marex@denx.de wrote:
On 12/18/19 3:06 AM, Joe Hershberger wrote:
On Tue, Dec 17, 2019 at 1:04 PM Marek Vasut marex@denx.de wrote:
On 12/17/19 7:47 PM, Joe Hershberger wrote: > On Tue, Dec 17, 2019 at 11:46 AM Marek Vasut marex@denx.de
wrote:
>> >> On 12/17/19 5:25 PM, Joe Hershberger wrote: >>> Hi Marek, >> >> Hi Joe, >> >>> On Tue, Dec 17, 2019 at 1:39 AM Marek Vasut marex@denx.de
wrote:
>>>> >>>> On 11/7/19 9:04 PM, Joe Hershberger wrote: >>>>> On Thu, Nov 7, 2019 at 1:16 PM Tom Rini trini@konsulko.com
wrote:
>>>>>> >>>>>> On Tue, Nov 05, 2019 at 04:05:11AM +0000, Priyanka Jain wrote: >>>>>> >>>>>>> Fix 'mask' calculation in phy_connect() for phy addr '0'. >>>>>>> 'mask' is getting set to '0xffffffff' for phy addr '0' >>>>>>> in phy_connect() whereas expected value is '0'. >>>>>>> >>>>>>> >>>>>>> Signed-off-by: Priyanka Jain priyanka.jain@nxp.com >>>>>> >>>>>> Reported-by: tetsu-aoki via github >>>>> >>>>> Acked-by: Joe Hershberger joe.hershberger@ni.com >>>> >>>> Sadly, this breaks systems where a PHY is at address 0. >>>> I have such an STM32MP1 system with LAN8720 PHY and since this >>>> patch, I cannot use ethernet. Please revert. >>> >>> It seems like a case that shouldn't have worked before. >> >> Eh? PHY at address 0 definitely did work before and must work now. > > Agreed that a phy at address 0 should work. Not agreed that > because the value "0" used to work due to a bug that it must > still. Which of these is the statement you are making? Do we > already agree or disagree?
I am saying that because a board worked on rc4 and does not work on rc5, this is a bug introduced by this patch in rc5 and must be fixed before the release.
The address 0 is a PHY broadcast address for some PHYs, it's a fixed address for other PHYs. Thus, a PHY at address 0 must work. If this is broken now, it's a bug.
The only thing this patch should change is to not access addresses other than 0. I read the data sheet for the LAN8720 and it doesn't mention anything about any broadcast behavior, so I'm not sure what you're trying to state here.
Read [1] section 3.7.1 PHYAD[2:0]: PHY ADDRESS CONFIGURATION
What I am saying is that there are two types of PHYs, ones which treat PHY address 0 as broadcast and ones which treat it as regular
address.
This one is the later and is configured as such in my case.
https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fww1.
microchip.com%2Fdownloads%2Fen%2FDeviceDoc%2F00002164B.pdf&da ta=0
2%7C01%7Cpriyanka.jain%40nxp.com%7C5270d34d955647ee66ea08d783d5ab c8%7
C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C1%7C637122826047859376&a mp;sd
ata=s22V5eU1kUe0030lbvWazQpooiM2OutlJbTxrPjbxs0%3D&reserved=0
I see. What's an example of a phy that treats 0 as broadcast?
IIRC KSZ9031 does.
>>> What about >>> this board requires the mask to be all 'f's, other than >>> specifying the wrong phy address? It seems that in your case the >>> phy address is not actually 0 (or the computed mask would find >>> it), but your board dts may be setting it to 0 as an "unknown" >>> value, but the correct unknown value should be "-1". It seems the
issue is with these boards.
>> >> Nope, the address is actually configured to 0 in hardware. > > Can you double check that?
No, sorry, I know the hardware is fixed to 0. Checking it again will not change this fact.
It seems there is no phy driver for this in U-Boot so the generic behavior is being used. I'm at a disadvantage of not having this board to try. Can you revert this patch and run with debug enabled for drivers/net/phy/phy.c to determine what is happening for this board? I would appreciate you helping with this.
It only says "connected to Generic PHY" .
So looking at the commit message, I am not really sure which board or issue does this patch fix. But if I understand the commit message right, then the aim is to set mask to 0 instead of 0xffffffff for address 0. But that's not right either, the mask should be BIT(0) = 1 for address 0, and that's what the patch actually does. I guess this then fails somewhere further down the road ...
Yes, the commit message is wrong... the expected value is 1, not 0. I missed that in the review.
Is the patch you sent earlier a solution for your board or something unrelated you found as a result of this discussion?
It works for my board, but I wonder how many other boards got broken here.
I also realized a mistake in commit message . The value of mask will be 1.
This current patch was basically a fix to an issue reported at https://github.com/u-boot/u-boot/commit/afbc31948a007e03d6a1282677aafc2208f4... introduced by commit afbc31948a007e03d6a1282677aafc2208f45819 (net: phy: implement fallback mechanism for negative phy addresses) Before this commit, the argument value passed to phy_find_by_mask() in phy_connect() for phy addr '0' was '1' , so this current patch tries to revert to same value '1'. So, not sure how has this current patch has introduced the issue . Via git log, I can see many other commits related to phy_id '0'. I don’t have the board which is broken because of this current patch. So, need help in analysis and proper fix.
Thanks Priyanka
The fix is OK, the issue is that some of the drivers were using addr 0 in phy_connect() to trigger a MDIO bus scan, not to connect to PHY @ addr 0. I am using a board with a PHY @ addr 0 and it works fine.
Grepping though the code it seems a couple of drivers hardcode addr 0: - dwc_eth_qos already solved by Marek in a separate patch, - bcm-sf2-eth.
Other drivers may use 0 but passed though a variable, those are harder to spot.
Converting bcm-sf2-eth to phy_connect(-1) may be OK, it would work like it did before this patch.
Alex