linux-kernel - Re: [PATCH AUTOSEL 6.8 39/68] net: mdio: mdio-bcm-unimac: Manage clock around I/O accesses

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Date: Sun, 7 Apr 2024 19:37:12 -0400
From: Sasha Levin <sashal@...nel.org>
To: Florian Fainelli <florian.fainelli@...adcom.com>
Cc: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Jacob Keller <jacob.e.keller@...el.com>,
	"David S . Miller" <davem@...emloft.net>, opendmb@...il.com,
	andrew@...n.ch, hkallweit1@...il.com, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 6.8 39/68] net: mdio: mdio-bcm-unimac: Manage
 clock around I/O accesses

On Tue, Apr 02, 2024 at 05:41:44AM -0700, Florian Fainelli wrote:
>
>
>On 3/29/2024 5:25 AM, Sasha Levin wrote:
>>From: Florian Fainelli <florian.fainelli@...adcom.com>
>>
>>[ Upstream commit ee975351cf0c2a11cdf97eae58265c126cb32850 ]
>>
>>Up until now we have managed not to have the mdio-bcm-unimac manage its
>>clock except during probe and suspend/resume. This works most of the
>>time, except where it does not.
>>
>>With a fully modular build, we can get into a situation whereby the
>>GENET driver is fully registered, and so is the mdio-bcm-unimac driver,
>>however the Ethernet PHY driver is not yet, because it depends on a
>>resource that is not yet available (e.g.: GPIO provider). In that state,
>>the network device is not usable yet, and so to conserve power, the
>>GENET driver will have turned off its "main" clock which feeds its MDIO
>>controller.
>>
>>When the PHY driver finally probes however, we make an access to the PHY
>>registers to e.g.: disable interrupts, and this causes a bus error
>>within the MDIO controller space because the MDIO controller clock(s)
>>are turned off.
>>
>>To remedy that, we manage the clock around all of the I/O accesses to
>>the hardware which are done exclusively during read, write and clock
>>divider configuration.
>>
>>This ensures that the register space is accessible, and this also
>>ensures that there are not unnecessarily elevated reference counts
>>keeping the clocks active when the network device is administratively
>>turned off. It would be the case with the previous way of managing the
>>clock.
>>
>>Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>
>>Signed-off-by: Florian Fainelli <florian.fainelli@...adcom.com>
>>Signed-off-by: David S. Miller <davem@...emloft.net>
>>Signed-off-by: Sasha Levin <sashal@...nel.org>
>
>Please drop this patch, it is usable in isolation and needs 2 
>additional patches to be meaningful:
>
>https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ee2b4cf8b281606bbf332cbd73ce2a73eac417f0
>https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>/commit/?id=ba0b78371c46b2104197ff2c244f13f011ddfa80

Ack, thanks!

-- 
Thanks,
Sasha