linux-kernel - Re: [PATCH 1/5 V4] PCI: define a function to check and wait till port finish DPC handling

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Message-ID: <CAHp75Vc_7RRtYv0HzqXqZO=hbN+tSFirxakJGkA1qYXZt676ZQ@mail.gmail.com>
Date:   Sun, 27 Sep 2020 12:05:26 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Ethan Zhao <haifeng.zhao@...el.com>,
        Dave Hansen <dave.hansen@...el.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, Oliver <oohall@...il.com>,
        ruscur@...sell.cc, Lukas Wunner <lukas@...ner.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Stuart Hayes <stuart.w.hayes@...il.com>,
        Alexandru Gagniuc <mr.nuke.me@...il.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        linux-pci <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        pei.p.jia@...el.com, ashok.raj@...ux.intel.com,
        Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Joe Perches <joe@...ches.com>
Subject: Re: [PATCH 1/5 V4] PCI: define a function to check and wait till port
 finish DPC handling

On Sun, Sep 27, 2020 at 11:33 AM Ethan Zhao <haifeng.zhao@...el.com> wrote:
>
> Once root port DPC capability is enabled and triggered, at the beginning
> of DPC is triggered, the DPC status bits are set by hardware and then
> sends DPC/DLLSC/PDC interrupts to OS DPC and pciehp drivers, it will
> take the port and software DPC interrupt handler 10ms to 50ms (test data
> on ICS(Ice Lake SP platform, see
> https://en.wikichip.org/wiki/intel/microarchitectures/ice_lake_(server)
> & stable 5.9-rc6) to complete the DPC containment procedure
> till the DPC status is cleared at the end of the DPC interrupt handler.
>
> We use this function to check if the root port is in DPC handling status
> and wait till the hardware and software completed the procedure.
>
> Signed-off-by: Ethan Zhao <haifeng.zhao@...el.com>
> Tested-by: Wen Jin <wen.jin@...el.com>
> Tested-by: Shanshan Zhang <ShanshanX.Zhang@...el.com>

> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

I haven't given you this tag. Where did you get it from?
(Dave, that's the case where we need to push the [internal review] process)

> Reviewed-by: Christoph Hellwig <hch@...radead.org>
> ---
> changes:
>  V2：align ICS code name to public doc.
>  V3: no change.
>  V4: response to Christoph's (Christoph Hellwig <hch@...radead.org>)
>      tip, move pci_wait_port_outdpc() to DPC driver and its declaration
>      to pci.h.
>
>  drivers/pci/pci.h      |  2 ++
>  drivers/pci/pcie/dpc.c | 27 +++++++++++++++++++++++++++
>  2 files changed, 29 insertions(+)
>
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index fa12f7cbc1a0..8fdb0d823d5a 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -455,10 +455,12 @@ void pci_restore_dpc_state(struct pci_dev *dev);
>  void pci_dpc_init(struct pci_dev *pdev);
>  void dpc_process_error(struct pci_dev *pdev);
>  pci_ers_result_t dpc_reset_link(struct pci_dev *pdev);
> +bool pci_wait_port_outdpc(struct pci_dev *pdev);
>  #else
>  static inline void pci_save_dpc_state(struct pci_dev *dev) {}
>  static inline void pci_restore_dpc_state(struct pci_dev *dev) {}
>  static inline void pci_dpc_init(struct pci_dev *pdev) {}
> +inline bool pci_wait_port_outdpc(struct pci_dev *pdev) { return false; }
>  #endif
>
>  #ifdef CONFIG_PCI_ATS
> diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
> index daa9a4153776..2e0e091ce923 100644
> --- a/drivers/pci/pcie/dpc.c
> +++ b/drivers/pci/pcie/dpc.c
> @@ -71,6 +71,33 @@ void pci_restore_dpc_state(struct pci_dev *dev)
>         pci_write_config_word(dev, dev->dpc_cap + PCI_EXP_DPC_CTL, *cap);
>  }
>
> +bool pci_wait_port_outdpc(struct pci_dev *pdev)
> +{
> +       u16 cap = pdev->dpc_cap, status;
> +       u16 loop = 0;
> +
> +       if (!cap) {
> +               pci_WARN_ONCE(pdev, !cap, "No DPC capability initiated\n");
> +               return false;
> +       }
> +       pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status);
> +       pci_dbg(pdev, "DPC status %x, cap %x\n", status, cap);
> +
> +       while (status & PCI_EXP_DPC_STATUS_TRIGGER && loop < 100) {
> +               msleep(10);
> +               loop++;
> +               pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status);
> +       }
> +
> +       if (!(status & PCI_EXP_DPC_STATUS_TRIGGER)) {
> +               pci_dbg(pdev, "Out of DPC %x, cost %d ms\n", status, loop*10);
> +               return true;
> +       }
> +
> +       pci_dbg(pdev, "Timeout to wait port out of DPC status\n");
> +       return false;
> +}
> +
>  static int dpc_wait_rp_inactive(struct pci_dev *pdev)
>  {
>         unsigned long timeout = jiffies + HZ;
> --
> 2.18.4
>


-- 
With Best Regards,
Andy Shevchenko