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From: Andrew Lunn <andrew@lunn.ch>
To: Ravi Gunasekaran <r-gunasekaran@ti.com>
Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
	pabeni@redhat.com, linux-omap@vger.kernel.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, kishon@ti.com,
	vigneshr@ti.com
Subject: Re: [PATCH v2 net-next] net: ethernet: ti: davinci_mdio: Add workaround for errata i2329
Date: Fri, 12 Aug 2022 17:54:33 +0200	[thread overview]
Message-ID: <YvZ3uc0xi18C1g5t@lunn.ch> (raw)
In-Reply-To: <ed3554bc-af62-78ce-a3eb-ff5f27ade6a2@ti.com>

> sh_eth is not configured for autosuspend and uses only pm_runtime_put().

I don't know the runtime power management code very well. We should
probably ask somebody how does. However:

https://elixir.bootlin.com/linux/latest/source/drivers/base/power/runtime.c#L168

This suggests it should be safe to perform an auto suspend on a device
which is not configured for auto suspend. To me, it looks like is
should directly suspend.

Devices are in a tree. If you suspend a leaf, you can walk up the tree
and suspend its parent as well, if it is not needed. Similarly, if you
wake a leaf, you need its parents awake as well, so you need to walk
up the tree and wake them. In order for this to work reliably, i
expect runtime PM to be very tolerant. If a device is not configured
for runtime PM, actions should be a NOP. If it is not configured for
auto suspend, and you ask it to auto suspend, to me, it would make
sense for it to immediately suspend, etc.

> Please provide your views on this. Your inputs on the next course of action
> would be helpful.

I would suggest you talk to somebody who knows about runtime PM.

  Andrew

WARNING: multiple messages have this Message-ID (diff)
From: Andrew Lunn <andrew@lunn.ch>
To: Ravi Gunasekaran <r-gunasekaran@ti.com>
Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
	pabeni@redhat.com, linux-omap@vger.kernel.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, kishon@ti.com,
	vigneshr@ti.com
Subject: Re: [PATCH v2 net-next] net: ethernet: ti: davinci_mdio: Add workaround for errata i2329
Date: Fri, 12 Aug 2022 17:54:33 +0200	[thread overview]
Message-ID: <YvZ3uc0xi18C1g5t@lunn.ch> (raw)
In-Reply-To: <ed3554bc-af62-78ce-a3eb-ff5f27ade6a2@ti.com>

> sh_eth is not configured for autosuspend and uses only pm_runtime_put().

I don't know the runtime power management code very well. We should
probably ask somebody how does. However:

https://elixir.bootlin.com/linux/latest/source/drivers/base/power/runtime.c#L168

This suggests it should be safe to perform an auto suspend on a device
which is not configured for auto suspend. To me, it looks like is
should directly suspend.

Devices are in a tree. If you suspend a leaf, you can walk up the tree
and suspend its parent as well, if it is not needed. Similarly, if you
wake a leaf, you need its parents awake as well, so you need to walk
up the tree and wake them. In order for this to work reliably, i
expect runtime PM to be very tolerant. If a device is not configured
for runtime PM, actions should be a NOP. If it is not configured for
auto suspend, and you ask it to auto suspend, to me, it would make
sense for it to immediately suspend, etc.

> Please provide your views on this. Your inputs on the next course of action
> would be helpful.

I would suggest you talk to somebody who knows about runtime PM.

  Andrew

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2022-08-12 15:54 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-10 11:13 [PATCH v2 net-next] net: ethernet: ti: davinci_mdio: Add workaround for errata i2329 Ravi Gunasekaran
2022-08-10 11:13 ` Ravi Gunasekaran
2022-08-11  0:30 ` Andrew Lunn
2022-08-11  0:30   ` Andrew Lunn
2022-08-11  7:00   ` Ravi Gunasekaran
2022-08-11  7:00     ` Ravi Gunasekaran
2022-08-11 12:57     ` Andrew Lunn
2022-08-11 12:57       ` Andrew Lunn
2022-08-12  4:36       ` Ravi Gunasekaran
2022-08-12  4:36         ` Ravi Gunasekaran
2022-08-12 15:54         ` Andrew Lunn [this message]
2022-08-12 15:54           ` Andrew Lunn
2022-08-16  4:26           ` Ravi Gunasekaran
2022-08-16  4:26             ` Ravi Gunasekaran
2022-08-13  0:57 ` kernel test robot
2022-08-13  0:57   ` kernel test robot

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