linux-kernel - Re: [RFC] net: stmmac: Problem with adding the native GPIOs support

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Date:   Wed, 16 Dec 2020 08:31:34 +0300
From:   Serge Semin <Sergey.Semin@...kalelectronics.ru>
To:     Andrew Lunn <andrew@...n.ch>
CC:     Serge Semin <fancer.lancer@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        <netdev@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-kernel@...r.kernel.org>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Jose Abreu <joabreu@...opsys.com>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Vyacheslav Mitrofanov 
        <Vyacheslav.Mitrofanov@...kalelectronics.ru>,
        "David S. Miller" <davem@...emloft.net>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC] net: stmmac: Problem with adding the native GPIOs support

On Wed, Dec 16, 2020 at 03:03:55AM +0100, Andrew Lunn wrote:
> > > From what you are saying, it sounds like from software you cannot
> > > independently control the GPIO controller reset?
> > 
> > No. The hardware implements the default MAC reset behavior. So the
> > GPIO controller gets reset synchronously with the MAC reset and that
> > can't be changed.
> 

> Is there pinmux support for these pins?  Can you disconnect them from
> the MAC? Often pins can be connected to different internal IP
> blocks. Maybe you can flip the pin mux, perform the MAC reset, and
> then put the pinmux back to connect the pins to the MAC IP again?

Alas no. Pins multiplexing isn't implemented in the Baikal-T1 SoC at all.
Each pin has been assigned with a single function. In this case DW GMAC
GPO/GPI pins always serve as GPO/GPI and nothing else.

-Sergey

> 
>      Andrew