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SubjectRe: [PATCH net-next v3 1/6] net: phy: mscc: migrate to phy_select/restore_page functions
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On Nov 19 2018, Andrew Lunn <andrew@lunn.ch> wrote:

> On Mon, Nov 19, 2018 at 03:57:17PM +0100, Andreas Schwab wrote:
>> On Okt 08 2018, Quentin Schulz <quentin.schulz@bootlin.com> wrote:
>>
>> > The Microsemi PHYs have multiple banks of registers (called pages).
>> > Registers can only be accessed from one page, if we need a register from
>> > another page, we need to switch the page and the registers of all other
>> > pages are not accessible anymore.
>> >
>> > Basically, to read register 5 from page 0, 1, 2, etc., you do the same
>> > phy_read(phydev, 5); but you need to set the desired page beforehand.
>> >
>> > In order to guarantee that two concurrent functions do not change the
>> > page, we need to do some locking per page. This can be achieved with the
>> > use of phy_select_page and phy_restore_page functions but phy_write/read
>> > calls in-between those two functions shall be replaced by their
>> > lock-free alternative __phy_write/read.
>> >
>> > Let's migrate this driver to those functions.
>>
>> This has some serious locking problem.
>
> Hi Andreas
>
> Could you be more specific. Are you getting a deadlock? A WARN_ON?

See the stack trace. That's where it hangs.

Andreas.

--
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

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