[PATCH v3] arm64: dts: rockchip: increase gmac rx_delay on rk3399-puma

[Quentin Schulz]

Hi Jakob,

On 12/5/24 4:18 PM, Jakob Unterwurzacher wrote:
> During mass manufacturing, we noticed the mmc_rx_crc_error counter,
> as reported by "ethtool -S eth0 | grep mmc_rx_crc_error", to increase
> above zero during nuttcp speedtests. Most of the time, this did not
> affect the achieved speed, but it prompted this investigation.
> 
> Cycling through the rx_delay range on six boards (see table below) of
> various ages shows that there is a large good region from 0x12 to 0x35
> where we see zero crc errors on all tested boards.
> 
> The old rx_delay value (0x10) seems to have always been on the edge for
> the KSZ9031RNX that is usually placed on Puma.
> 
> Choose "rx_delay = 0x23" to put us smack in the middle of the good
> region. This works fine as well with the KSZ9131RNX PHY that was used
> for a small number of boards during the COVID chip shortages.
> 
> 	Board S/N        PHY        rx_delay good region
> 	---------        ---        --------------------
> 	Puma TT0069903   KSZ9031RNX 0x11 0x35
> 	Puma TT0157733   KSZ9031RNX 0x11 0x35
> 	Puma TT0681551   KSZ9031RNX 0x12 0x37
> 	Puma TT0681156   KSZ9031RNX 0x10 0x38
> 	Puma 17496030079 KSZ9031RNX 0x10 0x37 (Puma v1.2 from 2017)
> 	Puma TT0681720   KSZ9131RNX 0x02 0x39 (alternative PHY used in very few boards)
> 
> 	Intersection of good regions = 0x12 0x35
> 	Middle of good region = 0x23
> 
> Relates-to: PUMA-111
> Fixes: 2c66fc34e945 ("arm64: dts: rockchip: add RK3399-Q7 (Puma) SoM")
> Cc: <stable at vger.kernel.org>
> Reviewed-by: Quentin Schulz <quentin.schulz at cherry.de>
> Signed-off-by: Jakob Unterwurzacher <jakob.unterwurzacher at cherry.de>

I had reported errors on my v2.1 Puma (KSZ9031) but none on my v2.3 
before that patch, and have 0 after applying this patch on both, so 
improvement for v2.1 and no regression for v2.3.

I ran the nuttcp test for an hour, failed after a minute on master 
(without the patch) on v2.1 but not on v2.3 and it didn't report any 
issue after an hour after applying this patch, thus:

Tested-by: Quentin Schulz <quentin.schulz at cherry.de> # Puma v2.1/v2.3 
with KSZ9031

I assume Krzysztof complained about their old email address appearing in 
the Cc list (it was changed in 6.9 in MAINTAINERS file) which 
highlighted you didn't develop on master (I did test on master though). 
Please address their concern from their mail and send a v4.

Thanks!
Quentin