lkml.org 
[lkml]   [2019]   [Nov]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] [RFC] r8169: check for valid MAC before clobbering
From
Date
On 13.11.2019 01:58, Brian Norris wrote:
> I have some old systems with RTL8168g Ethernet, where the BIOS (based on
> Coreboot) programs the MAC address into the MAC0 registers (at offset
> 0x0 and 0x4). The relevant Coreboot source is publicly available here:
>
> https://review.coreboot.org/cgit/coreboot.git/tree/src/mainboard/google/jecht/lan.c?h=4.10#n139
>
> (The BIOS is built off a much older branch, but the code is effectively
> the same.)
>
> Note that this was apparently the recommended solution in an application
> note at the time (I have a copy, but it's not marked for redistribution
> :( ), with no mention of the method used in rtl_read_mac_address().
>
The application note refers to RTL8105e which is quite different from
RTL8168g. For RTL8168g the BIOS has to write the MAC to the respective
GigaMAC registers, see rtl_read_mac_address for these registers.

If recompiling the BIOS isn't an option, then easiest should be to
change the MAC after boot with "ifconfig" or "ip" command.

> The result is that ever since commit 89cceb2729c7 ("r8169:add support
> more chips to get mac address from backup mac address register"), my MAC
> address changes to use an address I never intended.
>
> Unfortunately, these commits don't really provide any documentation, and
> I'm not sure when the recommendation actually changed. So I'm sending
> this as RFC, in case I can get any tips from Realtek on how to avoid
> breaking compatibility like this.
>
> I'll freely admit that the devices in question are currently pinned to
> an ancient kernel. We're only recently testing newer kernels on these
> devices, which brings me here.
>
> I'll also admit that I don't have much means to test this widely, and
> I'm not sure what implicit behaviors other systems were depending on
> along the way.
>
> Fixes: 89cceb2729c7 ("r8169:add support more chips to get mac address from backup mac address register")
> Fixes: 6e1d0b898818 ("r8169:add support for RTL8168H and RTL8107E")
> Cc: Chun-Hao Lin <hau@realtek.com>
> Signed-off-by: Brian Norris <briannorris@chromium.org>
> ---
> drivers/net/ethernet/realtek/r8169_main.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> index c4e961ea44d5..94067cf30514 100644
> --- a/drivers/net/ethernet/realtek/r8169_main.c
> +++ b/drivers/net/ethernet/realtek/r8169_main.c
> @@ -7031,11 +7031,14 @@ static void rtl_init_mac_address(struct rtl8169_private *tp)
> if (!rc)
> goto done;
>
> - rtl_read_mac_address(tp, mac_addr);
> + /* Check first to see if (e.g.) bootloader already programmed
> + * something.
> + */
> + rtl_read_mac_from_reg(tp, mac_addr, MAC0);
> if (is_valid_ether_addr(mac_addr))
> goto done;
>
> - rtl_read_mac_from_reg(tp, mac_addr, MAC0);
> + rtl_read_mac_address(tp, mac_addr);
> if (is_valid_ether_addr(mac_addr))
> goto done;
>
>

\
 
 \ /
  Last update: 2019-11-13 21:31    [W:0.165 / U:6.976 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site