linux-kernel - Re: [RESEND PATCH net-next v3 2/4] net: phy: aquantia: wait for FW reset before checking the vendor ID

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Message-ID: <20240806113622.g5ixwcwiw3vpidc3@skbuf>
Date: Tue, 6 Aug 2024 14:36:22 +0300
From: Vladimir Oltean <vladimir.oltean@....com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Jon Hunter <jonathanh@...dia.com>, Bartosz Golaszewski <brgl@...ev.pl>,
	Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Brad Griffis <bgriffis@...dia.com>
Subject: Re: [RESEND PATCH net-next v3 2/4] net: phy: aquantia: wait for FW
 reset before checking the vendor ID

Hi Russell,

On Tue, Jul 30, 2024 at 12:23:45PM +0100, Russell King (Oracle) wrote:
> > If it times out, then it would appear that with the above code we don't
> > attempt to load the firmware by any other means?
> 
> I'm also wondering about aqr_wait_reset_complete(). It uses
> phy_read_mmd_poll_timeout(), which prints an error message if it times
> out (which means no firmware has been loaded.) If we're then going on to
> attempt to load firmware, the error is not an error at all. So, I think
> while phy_read_poll_timeout() is nice and convenient, we need something
> like:
> 
> #define phy_read_poll_timeout_quiet(phydev, regnum, val, cond, sleep_us, \
>                                     timeout_us, sleep_before_read) \
> ({ \
>         int __ret, __val; \
>         __ret = read_poll_timeout(__val = phy_read, val, \
>                                   __val < 0 || (cond), \
>                 sleep_us, timeout_us, sleep_before_read, phydev, regnum); \
>         if (__val < 0) \
>                 __ret = __val; \
>         __ret; \
> })
> 
> #define phy_read_poll_timeout(phydev, regnum, val, cond, sleep_us, \
>                                 timeout_us, sleep_before_read) \
> ({ \
>         int __ret = phy_read_poll_timeout_quiet(phydev, regnum, val, cond, \
> 						sleep_us, timeout_us, \
> 						sleep_before_read); \
>         if (__ret) \
>                 phydev_err(phydev, "%s failed: %d\n", __func__, __ret); \
>         __ret; \
> })
> 
> and aqr_wait_reset_complete() needs to use phy_read_poll_timeout_quiet().

I agree that aqr_wait_reset_complete() shouldn't have built-in prints in it,
as long as failures are also expected. Maybe an alternative option would
be for aqr_wait_reset_complete() to manually roll a call to read_poll_timeout(),
considering how it would be nice for _actual_ errors (not -ETIMEDOUT)
from phy_read_mmd() to still be logged.

But it seems strange that the driver has to time out on a 2 second poll,
and then it's still not sure why VEND1_GLOBAL_FW_ID still reads 0?
Is it because there's no firmware, or because there is, but it hasn't
waited for long enough?

I haven't followed the development of AQR firmware loading. Isn't there
a faster and more reliable way of determining whether there is firmware
in the first place? It could give the driver a 2 second boot-time speedup,
plus more confidence.