[edk2-devel] [PATCH 1/2] Silicon/Broadcom/BcmGenetDxe: Delay for linkup in transmit
Ard Biesheuvel
ardb at kernel.org
Mon May 10 17:32:32 UTC 2021
On Mon, 10 May 2021 at 19:26, Jeremy Linton <jeremy.linton at arm.com> wrote:
>
> Hi,
>
> On 5/10/21 11:56 AM, Ard Biesheuvel wrote:
> > On Thu, 15 Apr 2021 at 21:22, Jeremy Linton <jeremy.linton at arm.com> wrote:
> >>
> >> Under normal circumstances GenetSimpleNetworkTransmit won't be
> >> called unless the rest of the network stack detects the link is
> >> up. So, during normal operation when the adapter is initialized
> >> the link naturally transitions to link up, and then is ready for
> >> activity later in the boot sequence. If that hasn't happened by
> >> the time PXE runs then it will itself wait for the link.
> >>
> >> OTOH, the normal distro PXE sequence involves PXE loading shim
> >> which in turn loads grub, which tries to read machine specific
> >> configs, modules, and grub.cfg in order to prepare the boot menu.
> >> Then, once a grub selection is picked, it might try to load the
> >> kernel+initrd.
> >>
> >> In this sequence the network stack is shutdown and restarted
> >> multiple times. Grub though, starts up, notices its been network
> >> booted, reads saved network parameters and immediately tries to
> >> transmit data assuming the link is still up.
> >>
> >> When that happens grub will print "couldn't send network packet"
> >> and if that lasts long enough it fails to load grub.cfg and the
> >> user gets dropped to the grub prompt because no one in the path
> >> bothers to assure the link state has transitioned back up.
> >>
> >
> > This is an excellent problem description. Could we dedicate a couple
> > of paragraphs to the solution as well? Especially given that 'wait for
> > random # of seconds' seems to be the taken approach here, which seems
> > a bit sloppy to me, given that we should be able to detect whether the
> > link is up, no?
>
> Isn't that what GenericPhyUpdateConfig is doing? Checking for linkup,
> and updating the phy state? So once the link goes up, it return
> EFI_SUCCESS and the loop terminates.
>
OK. Could you dedicate some prose to this logic in the commit log please?
> I was actually a bit concerned that the 10s wasn't enough since AFAIK a
> large part of the delay is the remote side.
>
The remote side of what? The Ethernet cable?
>
>
> >
> >
> >
> >> For reference: https://github.com/pftf/RPi4/issues/113
> >>
> >> Signed-off-by: Jeremy Linton <jeremy.linton at arm.com>
> >> ---
> >> .../Drivers/Net/BcmGenetDxe/SimpleNetwork.c | 24 ++++++++++++++++++++--
> >> 1 file changed, 22 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/SimpleNetwork.c b/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/SimpleNetwork.c
> >> index 1bda18f157..29c76d8495 100644
> >> --- a/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/SimpleNetwork.c
> >> +++ b/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/SimpleNetwork.c
> >> @@ -13,6 +13,7 @@
> >> #include <Library/DebugLib.h>
> >> #include <Library/DmaLib.h>
> >> #include <Library/NetLib.h>
> >> +#include <Library/UefiBootServicesTableLib.h>
> >> #include <Protocol/SimpleNetwork.h>
> >>
> >> #include "BcmGenetDxe.h"
> >> @@ -590,9 +591,28 @@ GenetSimpleNetworkTransmit (
> >>
> >> if (!Genet->SnpMode.MediaPresent) {
> >> //
> >> - // Don't bother transmitting if there's no link.
> >> + // We should only really get here if the link was up
> >> + // and is now down due to a stop/shutdown sequence, and
> >> + // the app (grub) doesn't bother to check link state
> >> + // because it was up a moment before.
> >> + // Lets wait a bit for the link to resume, rather than
> >> + // failing to send. In the case of grub it works either way
> >> + // but we can't be sure that is universally true, and
> >> + // hanging for a couple seconds is nicer than a screen of
> >> + // grub send failure messages.
> >> //
> >> - return EFI_NOT_READY;
> >> + int retries = 1000;
> >> + DEBUG ((DEBUG_INFO, "%a: Waiting 10s for link\n", __FUNCTION__));
> >> + do {
> >> + gBS->Stall (10000);
> >> + Status = GenericPhyUpdateConfig (&Genet->Phy);
> >> + } while (EFI_ERROR (Status) && retries--);
> >> + if (EFI_ERROR (Status)) {
> >> + DEBUG ((DEBUG_ERROR, "%a: no link\n", __FUNCTION__));
> >> + return EFI_NOT_READY;
> >> + } else {
> >> + Genet->SnpMode.MediaPresent = TRUE;
> >> + }
> >> }
> >>
> >> if (HeaderSize != 0) {
> >> --
> >> 2.13.7
> >>
> >>
> >>
> >>
> >>
> >>
>
-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#74905): https://edk2.groups.io/g/devel/message/74905
Mute This Topic: https://groups.io/mt/82125863/1813853
Group Owner: devel+owner at edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [edk2-devel-archive at redhat.com]
-=-=-=-=-=-=-=-=-=-=-=-
More information about the edk2-devel-archive
mailing list