netdev - Re: [PATCH net-next v1 2/2] net: phy: qt2025: wait until PHY becomes ready

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Message-Id: <20241002.111704.654457386762955005.fujita.tomonori@gmail.com>
Date: Wed, 02 Oct 2024 11:17:04 +0000 (UTC)
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: aliceryhl@...gle.com
Cc: fujita.tomonori@...il.com, netdev@...r.kernel.org,
 rust-for-linux@...r.kernel.org, andrew@...n.ch, hkallweit1@...il.com,
 tmgross@...ch.edu, ojeda@...nel.org, alex.gaynor@...il.com,
 gary@...yguo.net, bjorn3_gh@...tonmail.com, benno.lossin@...ton.me,
 a.hindborg@...sung.com
Subject: Re: [PATCH net-next v1 2/2] net: phy: qt2025: wait until PHY
 becomes ready

On Tue, 1 Oct 2024 13:36:41 +0200
Alice Ryhl <aliceryhl@...gle.com> wrote:

>> diff --git a/drivers/net/phy/qt2025.rs b/drivers/net/phy/qt2025.rs
>> index 28d8981f410b..3a8ef9f73642 100644
>> --- a/drivers/net/phy/qt2025.rs
>> +++ b/drivers/net/phy/qt2025.rs
>> @@ -93,8 +93,15 @@ fn probe(dev: &mut phy::Device) -> Result<()> {
>>          // The micro-controller will start running from SRAM.
>>          dev.write(C45::new(Mmd::PCS, 0xe854), 0x0040)?;
>>
>> -        // TODO: sleep here until the hw becomes ready.
>> -        Ok(())
>> +        // sleep here until the hw becomes ready.
>> +        for _ in 0..60 {
>> +            kernel::delay::sleep(core::time::Duration::from_millis(50));
>> +            let val = dev.read(C45::new(Mmd::PCS, 0xd7fd))?;
>> +            if val != 0x00 && val != 0x10 {
>> +                return Ok(());
>> +            }
> 
> Why not place the sleep after this check? That way, we don't need to
> sleep if the check succeeds immediately.

Yeah, that's better. I copied the logic in the vendor driver without
thinking.

As Andrew pointed out, the code like this in C drivers isn't
recommended; iopoll.h should be used. So I'll try to implement such.


>> +        }
>> +        Err(code::ENODEV)
> 
> This sleeps for up to 3 seconds. Is that the right amount to sleep?

That's what the vendor driver does.