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[realtek] Work around hardware bug on RTL8211B

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The RTL8211B seems to have a bug that prevents the link from coming up
unless the MII_MMD_DATA register is cleared.

The Linux kernel driver applies this workaround (in rtl8211b_resume())
only to the specific RTL8211B PHY model, along with a matching
workaround to set bit 9 of MII_MMD_DATA when suspending the PHY.
Since we have no need to ever suspend the PHY, and since writing a
zero ought to be harmless, we just clear the register unconditionally.

Debugged-by: Nikolay Pertsev <nikolay.p@cos.flag.org>
Tested-by: Nikolay Pertsev <nikolay.p@cos.flag.org>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2021-06-22 14:48:10 +01:00
parent 0688114ea6
commit 5622575c5e
2 changed files with 12 additions and 0 deletions
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src/drivers/net/realtek.c
+10
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@@ -420,6 +420,16 @@ static int realtek_phy_reset ( struct realtek_nic *rtl ) {
*/
}
/* Some cards (e.g. RTL8211B) have a hardware errata that
* requires the MII_MMD_DATA register to be cleared before the
* link will come up.
*/
if ( ( rc = mii_write ( &rtl->mii, MII_MMD_DATA, 0 ) ) != 0 ) {
/* Ignore failures, since the register may not be
* present on all PHYs.
*/
}
/* Restart autonegotiation */
if ( ( rc = mii_restart ( &rtl->mii ) ) != 0 ) {
DBGC ( rtl, "REALTEK %p could not restart MII: %s\n",