linux-kernel - Re: [PATCH v1 net-next] net: stmmac: Add support for MDIO interrupts

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Date:   Mon, 26 Aug 2019 20:47:19 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Voon Weifeng <weifeng.voon@...el.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jose Abreu <joabreu@...opsys.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Ong Boon Leong <boon.leong.ong@...el.com>
Subject: Re: [PATCH v1 net-next] net: stmmac: Add support for MDIO interrupts

On Tue, Aug 27, 2019 at 09:45:20AM +0800, Voon Weifeng wrote:
> From: "Chuah, Kim Tatt" <kim.tatt.chuah@...el.com>
> 
> DW EQoS v5.xx controllers added capability for interrupt generation
> when MDIO interface is done (GMII Busy bit is cleared).
> This patch adds support for this interrupt on supported HW to avoid
> polling on GMII Busy bit.
> 
> stmmac_mdio_read() & stmmac_mdio_write() will sleep until wake_up() is
> called by the interrupt handler.

Hi Voon

I _think_ there are some order of operation issues here. The mdiobus
is registered in the probe function. As soon as of_mdiobus_register()
is called, the MDIO bus must work. At that point MDIO read/writes can
start to happen.

As far as i can see, the interrupt handler is only requested in
stmmac_open(). So it seems like any MDIO operations after probe, but
before open are going to fail?

Thanks
       Andrew