Hi,
On Fri 11 Sep 20, 09:25, Hamish Martin wrote:
> Some integrated OHCI controller hubs do not expose all ports of the hub
> to pins on the SoC. In some cases the unconnected ports generate
> spurious over-current events. For example the Broadcom 56060/Ranger 2 SoC
> contains a nominally 3 port hub but only the first port is wired.
>
> Default behaviour for ohci-platform driver is to use global over-current
> protection mode (AKA "ganged"). This leads to the spurious over-current
> events affecting all ports in the hub.
>
> We now alter the default to use per-port over-current protection.
This specific patch lead to breaking OHCI on my mom's laptop (whom was about
to buy a new one thinking the hardware had failed). I get no OHCI interrupt at
all and no USB 1 device is ever detected.
I haven't really found a reasonable explanation about why that is, but here
are some notes I was able to collect:
- The issue showed up on 5.8,18 and 5.9.15, which don't include the patch
from this series that sets distrust_firmware = false; This results in the NPS
bit being set via OHCI_QUIRK_HUB_POWER.
- Adding val &= ~RH_A_PSM; (as was done before this change) solves the issue
which is weird because the bit is supposed to be inactive when NPS is set;
- Setting ohci_hcd.distrust_firmware=0 in the cmdline results in not setting
the NPS bit and also solves the issue;
- The initial value of the register at function entry is 0x1001104 (PSM bit
is set, NPS is unset);
- The OHCI controller is the following:
00:03.0 USB controller: Silicon Integrated Systems [SiS] USB 1.1 Controller (rev 0f) (prog-if 10 [OHCI])
Subsystem: ASUSTeK Computer Inc. Device 1aa7
Does that make any sense to you?
I really wonder what a proper fix could be and here are some suggestions:
- Adding a specific quirk to clear the PSM bit for this hardware which seems to
consider the bit regardless of NPS;
- Adding the patch that sets distrust_firmware = false to stable branches;
What do you think?
Cheers,
Paul
> This patch results in the following configuration changes depending
> on quirks:
> - For quirk OHCI_QUIRK_SUPERIO no changes. These systems remain set up
> for ganged power switching and no over-current protection.
> - For quirk OHCI_QUIRK_AMD756 or OHCI_QUIRK_HUB_POWER power switching
> remains at none, while over-current protection is now guaranteed to be
> set to per-port rather than the previous behaviour where it was either
> none or global over-current protection depending on the value at
> function entry.
>
> Suggested-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Hamish Martin <hamish.martin@xxxxxxxxxxxxxxxxxxx>
> ---
>
> Notes:
> Changes in v2:
> - remove clearing of RH_A_PSM in OHCI_QUIRK_HUB_POWER block.
>
> drivers/usb/host/ohci-hcd.c | 16 ++++++++++------
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci-hcd.c
> index dd37e77dae00..2845ea328a06 100644
> --- a/drivers/usb/host/ohci-hcd.c
> +++ b/drivers/usb/host/ohci-hcd.c
> @@ -673,20 +673,24 @@ static int ohci_run (struct ohci_hcd *ohci)
>
> /* handle root hub init quirks ... */
> val = roothub_a (ohci);
> - val &= ~(RH_A_PSM | RH_A_OCPM);
> + /* Configure for per-port over-current protection by default */
> + val &= ~RH_A_NOCP;
> + val |= RH_A_OCPM;
> if (ohci->flags & OHCI_QUIRK_SUPERIO) {
> - /* NSC 87560 and maybe others */
> + /* NSC 87560 and maybe others.
> + * Ganged power switching, no over-current protection.
> + */
> val |= RH_A_NOCP;
> - val &= ~(RH_A_POTPGT | RH_A_NPS);
> - ohci_writel (ohci, val, &ohci->regs->roothub.a);
> + val &= ~(RH_A_POTPGT | RH_A_NPS | RH_A_PSM | RH_A_OCPM);
> } else if ((ohci->flags & OHCI_QUIRK_AMD756) ||
> (ohci->flags & OHCI_QUIRK_HUB_POWER)) {
> /* hub power always on; required for AMD-756 and some
> - * Mac platforms. ganged overcurrent reporting, if any.
> + * Mac platforms.
> */
> val |= RH_A_NPS;
> - ohci_writel (ohci, val, &ohci->regs->roothub.a);
> }
> + ohci_writel(ohci, val, &ohci->regs->roothub.a);
> +
> ohci_writel (ohci, RH_HS_LPSC, &ohci->regs->roothub.status);
> ohci_writel (ohci, (val & RH_A_NPS) ? 0 : RH_B_PPCM,
> &ohci->regs->roothub.b);
> --
> 2.28.0
>
--
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com
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