linux-kernel - Re: [Linux-stm32] [PATCH v1 2/2] net: stmmac: Add NPCM support

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Date:   Thu, 30 Nov 2023 21:34:41 +0100
From:   Maxime Chevallier <maxime.chevallier@...tlin.com>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Tomer Maimon <tmaimon77@...il.com>,
        davem@...emloft.net, avifishman70@...il.com, venture@...gle.com,
        openbmc@...ts.ozlabs.org, robh+dt@...nel.org,
        tali.perry1@...il.com, mcoquelin.stm32@...il.com,
        edumazet@...gle.com, joabreu@...opsys.com, joel@....id.au,
        krzysztof.kozlowski+dt@...aro.org, peppe.cavallaro@...com,
        j.neuschaefer@....net, netdev@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, benjaminfair@...gle.com
Subject: Re: [Linux-stm32] [PATCH v1 2/2] net: stmmac: Add NPCM support

Hello,

On Thu, 30 Nov 2023 22:59:32 +0300
Serge Semin <fancer.lancer@...il.com> wrote:

> On Thu, Nov 30, 2023 at 06:26:13PM +0100, Andrew Lunn wrote:
> > > I will check with the xpcs maintainer how can we add indirect access
> > > to the xpcs module.  
> > 
> > https://elixir.bootlin.com/linux/latest/source/drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c#L449
> > 
> > It creates a regmap for the memory range. On top of that it creates an
> > MDIO bus. You can then access the PCS in the normal way.  
> 
> Actually Synopsys DW XPCS can be synthesized with two types of the CSR
> interfaces:
> 1. MDIO: device looks as a normal MDIO device. This option is currently
>    supported by the STMMAC MDIO driver.
> 2. MCI/APB3: device MMD CSRs are directly (all CSRs are visible) or
>    indirectly (paged-base access) accessible over the system memory bus.
> 
> In addition to the above XPCS device can be equipped with separate
> clock sources (at least to feed the MCI or APB3 interface) and may
> have dedicated IRQ line to signal various events like link
> establishing, failures, etc. From that perspective XPCS in both cases
> looks as a normal platform device for which would be better to have a
> special DT-node defined with all those resources supplied. Then the
> XPCS DT-node could be passed to the DW MAC DT-node via the already
> standardized "pcs-handle" DT-property.

To my understanding, this should work, there's another PCS that works
this way : 
https://elixir.bootlin.com/linux/v6.7-rc3/source/drivers/net/pcs/pcs-rzn1-miic.c

Are you still able to use the mdio-regmap glue that Andrew mentioned,
to avoid the duplication between the mdio and mmio register accesses ?

Maxime