Re: [PATCH net-next v2] net: pcs: rzn1-miic: Correct MODCTRL register offset

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Hi Wolfram,

On Thu, Aug 28, 2025 at 11:25 AM Wolfram Sang
<wsa+renesas@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, Aug 20, 2025 at 06:09:13PM +0100, Prabhakar wrote:
> > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> >
> > Correct the Mode Control Register (MODCTRL) offset for RZ/N MIIC.
> > According to the R-IN Engine and Ethernet Peripherals Manual (Rev.1.30)
> > [0], Table 10.1 "Ethernet Accessory Register List", MODCTRL is at offset
> > 0x8, not 0x20 as previously defined.
> >
> > Offset 0x20 actually maps to the Port Trigger Control Register (PTCTRL),
> > which controls PTP_MODE[3:0] and RGMII_CLKSEL[4]. Using this incorrect
> > definition prevented the driver from configuring the SW_MODE[4:0] bits
> > in MODCTRL, which control the internal connection of Ethernet ports. As
> > a result, the MIIC could not be switched into the correct mode, leading
> > to link setup failures and non-functional Ethernet ports on affected
> > systems.
> >
> > [0] https://www.renesas.com/en/document/mah/rzn1d-group-rzn1s-group-rzn1l-group-users-manual-r-engine-and-ethernet-peripherals?r=1054571
> >
> > Fixes: 7dc54d3b8d91 ("net: pcs: add Renesas MII converter driver")
> > Cc: stable@xxxxxxxxxx
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> > Reviewed-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
>
> I had a look now. Because the bootloader of my N1D board already set up
> MODCTRL correctly, this write to the wrong register went unnoticed. I
> verified that the now correctly written value (depending on DT config)
> matches the value previously set by the bootloader. As a result,
> everything keeps working. We were lucky. Or unlucky. Depending how you
> look at it.
>
Thank you for testing it. I'll send a v3 soon with `net-next` dropped
from the subject.

Cheers,
Prabhakar





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