Messages in this thread | | | Subject | Re: [PATCH v2 1/4] usb: early: Avoid using DbC if already enabled | From | Connor Davis <> | Date | Mon, 17 May 2021 07:48:52 -0600 |
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On 5/17/21 3:32 AM, Jan Beulich wrote: > On 14.05.2021 02:56, Connor Davis wrote: >> Check if the debug capability is enabled in early_xdbc_parse_parameter, >> and if it is, return with an error. This avoids collisions with whatever >> enabled the DbC prior to linux starting. > Doesn't this go too far and prevent use even if firmware (perhaps > mistakenly) left it enabled? > > Jan
Yes, but how is one supposed to distinguish the broken firmware and non-broken
firmware cases?
> >> Signed-off-by: Connor Davis <connojdavis@gmail.com> >> --- >> drivers/usb/early/xhci-dbc.c | 10 ++++++++++ >> 1 file changed, 10 insertions(+) >> >> diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c >> index be4ecbabdd58..ca67fddc2d36 100644 >> --- a/drivers/usb/early/xhci-dbc.c >> +++ b/drivers/usb/early/xhci-dbc.c >> @@ -642,6 +642,16 @@ int __init early_xdbc_parse_parameter(char *s) >> } >> xdbc.xdbc_reg = (struct xdbc_regs __iomem *)(xdbc.xhci_base + offset); >> >> + if (readl(&xdbc.xdbc_reg->control) & CTRL_DBC_ENABLE) { >> + pr_notice("xhci debug capability already in use\n"); >> + early_iounmap(xdbc.xhci_base, xdbc.xhci_length); >> + xdbc.xdbc_reg = NULL; >> + xdbc.xhci_base = NULL; >> + xdbc.xhci_length = 0; >> + >> + return -ENODEV; >> + } >> + >> return 0; >> } >> >> Thanks,
Connor
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