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SubjectRe: [PATCH v2 1/4] usb: early: Avoid using DbC if already enabled
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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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