linux-kernel - Re: [PATCH 3/3] net: stmmac: Add DWMAC glue layer for Renesas GBETH

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Message-ID: <CA+V-a8vCB7nP=tsv4UkOwODSs-9hiG-PxN6cpihfvwjq2itAHg@mail.gmail.com>
Date: Sun, 2 Mar 2025 21:20:49 +0000
From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Philipp Zabel <p.zabel@...gutronix.de>, Geert Uytterhoeven <geert+renesas@...der.be>, 
	Giuseppe Cavallaro <peppe.cavallaro@...com>, Jose Abreu <joabreu@...opsys.com>, 
	Alexandre Torgue <alexandre.torgue@...s.st.com>, netdev@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org, Biju Das <biju.das.jz@...renesas.com>, 
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH 3/3] net: stmmac: Add DWMAC glue layer for Renesas GBETH

Hi Russell,

On Sun, Mar 2, 2025 at 7:33 PM Russell King (Oracle)
<linux@...linux.org.uk> wrote:
>
> On Sun, Mar 02, 2025 at 06:18:08PM +0000, Prabhakar wrote:
> > +     gbeth->dev = dev;
> > +     gbeth->regs = stmmac_res.addr;
> > +     plat_dat->bsp_priv = gbeth;
> > +     plat_dat->set_clk_tx_rate = stmmac_set_clk_tx_rate;
>
> Thanks for using that!
>
Yep, it shortens the glue driver further.

> > +     plat_dat->flags |= STMMAC_FLAG_HWTSTAMP_CORRECT_LATENCY |
> > +                        STMMAC_FLAG_EN_TX_LPI_CLOCKGATING |
>
> I would like to know what value tx_clk_stop is in
> stmmac_mac_enable_tx_lpi() for your setup. Ideally, stmmac should
> use the capability report from the PHY to decide whether the
> transmit clock can be gated, but sadly we haven't had any support
> in phylib/phylink for that until recently, and I haven't modified
> stmmac to allow use of that. However, it would be good to gain
> knowledge in this area.
>
tx_clk_stop =1,

root@...2h-evk-alpha:~# ifconfig eth0 up
[  587.830436] renesas-gbeth 15c30000.ethernet eth0: Register
MEM_TYPE_PAGE_POOL RxQ-0
[  587.838636] renesas-gbeth 15c30000.ethernet eth0: Register
MEM_TYPE_PAGE_POOL RxQ-1
[  587.846792] renesas-gbeth 15c30000.ethernet eth0: Register
MEM_TYPE_PAGE_POOL RxQ-2
[  587.854734] renesas-gbeth 15c30000.ethernet eth0: Register
MEM_TYPE_PAGE_POOL RxQ-3
[  587.926860] renesas-gbeth 15c30000.ethernet eth0: PHY [stmmac-0:00]
driver [Microchip KSZ9131 Gigabit PHY] (irq=POLL)
[  587.949380] dwmac4: Master AXI performs fixed burst length
[  587.954910] renesas-gbeth 15c30000.ethernet eth0: No Safety
Features support found
[  587.962556] renesas-gbeth 15c30000.ethernet eth0: IEEE 1588-2008
Advanced Timestamp supported
[  587.971420] renesas-gbeth 15c30000.ethernet eth0: registered PTP clock
[  587.978004] renesas-gbeth 15c30000.ethernet eth0: configuring for
phy/rgmii-id link mode
root@...2h-evk-alpha:~# [  591.070448] renesas-gbeth 15c30000.ethernet
eth0: tx_clk_stop=1
[  591.076590] renesas-gbeth 15c30000.ethernet eth0: Link is Up -
1Gbps/Full - flow control rx/tx

With the below diff:

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index aec230353ac4..68f1954e6eea 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -1100,6 +1100,7 @@ static int stmmac_mac_enable_tx_lpi(struct
phylink_config *config, u32 timer,
        struct stmmac_priv *priv = netdev_priv(to_net_dev(config->dev));
        int ret;

+       netdev_err(priv->dev, "tx_clk_stop=%d\n", tx_clk_stop);
        priv->tx_lpi_timer = timer;
        priv->eee_active = true;

> > +                        STMMAC_FLAG_RX_CLK_RUNS_IN_LPI |
>
> What is the reason for setting this flag? If it's because of suspend/
> resume failures, does my "net: stmmac: fix resume failures due to
> RX clock" series solve this for you without requiring this flag?
>
Ive set this flag based on the configuration supported by this IP.
Unfortunately the platform which I am working on doesn't support s2r
yet so I cannot test suspend/resume path yet. But I do see an issue
when I unload and load just the glue module the DMA reset fails.

Cheers,
Prabhakar