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

From: Maxime Chevallier <maxime.chevallier@bootlin.com>
To: Serge Semin <fancer.lancer@gmail.com>
Cc: Andrew Lunn <andrew@lunn.ch>, Tomer Maimon <tmaimon77@gmail.com>,
	krzysztof.kozlowski+dt@linaro.org, devicetree@vger.kernel.org,
	avifishman70@gmail.com, venture@google.com,
	openbmc@lists.ozlabs.org,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-kernel@vger.kernel.org, joabreu@synopsys.com,
	tali.perry1@gmail.com, edumazet@google.com, robh+dt@kernel.org,
	joel@jms.id.au, mcoquelin.stm32@gmail.com, j.neuschaefer@gmx.net,
	peppe.cavallaro@st.com, netdev@vger.kernel.org,
	davem@davemloft.net, linux-arm-kernel@lists.infradead.org,
	benjaminfair@google.com
Subject: Re: [Linux-stm32] [PATCH v1 2/2] net: stmmac: Add NPCM support
Date: Thu, 30 Nov 2023 21:34:41 +0100	[thread overview]
Message-ID: <20231130213441.032a661c@device.home> (raw)
In-Reply-To: <xvy2coamb6cl3wcbkl32f6w7kksoxfocyd63t7k7bz4pne2gyx@lktivhqovy7p>

Hello,

On Thu, 30 Nov 2023 22:59:32 +0300
Serge Semin <fancer.lancer@gmail.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