Re: [PATCH v2 1/4] usb: early: Avoid using DbC if already enabled
From: Jan Beulich <hidden>
Date: 2021-05-17 09:31:57
Also in:
lkml, xen-devel
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
quoted hunk ↗ jump to hunk
Signed-off-by: Connor Davis <redacted> --- 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; }