From: Connor Davis <connojdavis@gmail.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: Jann Horn <jannh@google.com>, Lee Jones <lee.jones@linaro.org>,
Chunfeng Yun <chunfeng.yun@mediatek.com>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
xen-devel@lists.xenproject.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH v2 1/4] usb: early: Avoid using DbC if already enabled
Date: Mon, 17 May 2021 07:48:52 -0600 [thread overview]
Message-ID: <16400ee4-4406-8b26-10c0-a423b2b1fed0@gmail.com> (raw)
In-Reply-To: <8ccce25a-e3ca-cb30-f6a3-f9243a85a49b@suse.com>
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
next prev parent reply other threads:[~2021-05-17 13:48 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-14 0:56 [PATCH v2 0/4] Support xen-driven USB3 debug capability Connor Davis
2021-05-14 0:56 ` [PATCH v2 1/4] usb: early: Avoid using DbC if already enabled Connor Davis
2021-05-14 0:56 ` [PATCH v2 2/4] xen: Export dbgp functions when CONFIG_XEN_DOM0 is enabled Connor Davis
2021-05-14 14:06 ` Connor Davis
2021-05-14 0:56 ` [PATCH v2 3/4] usb: dbgp: Fix return values for reset prep and startup Connor Davis
2021-05-14 15:33 ` Boris Ostrovsky
2021-05-14 0:56 ` [PATCH v2 4/4] usb: xhci: Notify xen when DbC is unsafe to use Connor Davis
2021-05-17 9:32 ` [PATCH v2 1/4] usb: early: Avoid using DbC if already enabled Jan Beulich
2021-05-17 13:48 ` Connor Davis [this message]
2021-05-17 14:13 ` Jan Beulich
2021-05-17 14:24 ` Connor Davis
2021-05-18 21:50 ` Mathias Nyman
2021-05-14 6:46 ` [PATCH v2 0/4] Support xen-driven USB3 debug capability Greg Kroah-Hartman
2021-05-14 14:07 ` Connor Davis
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