On Tue, Mar 05, 2019 at 06:31:22PM +0100, Stefan Mätje wrote:
> Due to an erratum in some Pericom PCIe-to-PCI bridges in reverse mode the
> retrain link bit needs to be cleared again manually to allow the link
> training to complete successfully.
>
> If it is not cleared manually the link training is continuously restarted
> and all devices below the PCI-to-PCIe bridge can't be accessed any more.
> That means drivers for devices below the bridge will be loaded but won't
> work or even crash because the driver is only reading 0xffff.
>
> See the Pericom Errata Sheet PI7C9X111SLB_errata_rev1.2_102711.pdf for
> details.
>
> Devices known as affected so far are: PI7C9X110, PI7C9X111SL, PI7C9X130
>
> The patch introduces a new flag clear_retrain_link in the struct pci_dev. This
> flag is set in quirk_enable_clear_retrain_link() for the affected devices in
> the pci_fixup_header in quirks.c
>
> The link retraining code is moved to pcie_retrain_link(). This function now
> applies the work around to clear the PCI_EXP_LNKCTL_RL bit again if
> clear_retrain_link bit is set in the pci_dev structure of the link parent
> device.
> + /* Wait for link training end. Break out after waiting for timeout */
> + start_jiffies = jiffies;
> + for (;;) {
> + pcie_capability_read_word(parent, PCI_EXP_LNKSTA, ®16);
> + if (!(reg16 & PCI_EXP_LNKSTA_LT))
> + break;
> + if (time_after(jiffies, start_jiffies + LINK_RETRAIN_TIMEOUT))
> + break;
> + msleep(1);
> + }
I see this is existing code, though two comments (perhaps for future clean up):
- msleep(1) is not guaranteed to be 1 ms at all (in some cases it might be less)
- better to use do {} while (time_before()) loop
> +static void quirk_enable_clear_retrain_link(struct pci_dev *dev)
> +{
> + dev->clear_retrain_link = 1;
> + pci_info(dev, "Enable Pericom link retrain quirk\n");
If some other device would appear with same issue, but from another vendor this
becomes misleading.
I would recommend to refer to an issue the quirk is about, and not the vendor.
> +}
--
With Best Regards,
Andy Shevchenko
