Re: [RFC] [PATCH net-next v4] [PATCH 2/2] r8169: Implement dynamic ASPM mechanism

[Kai-Heng Feng <kai.heng.feng@canonical.com>]

On Tue, Sep 7, 2021 at 2:03 PM Heiner Kallweit <hkallweit1@gmail.com> wrote:
>
> On 27.08.2021 19:14, Kai-Heng Feng wrote:
> > r8169 NICs on some platforms have abysmal speed when ASPM is enabled.
> > Same issue can be observed with older vendor drivers.
> >
> > The issue is however solved by the latest vendor driver. There's a new
> > mechanism, which disables r8169's internal ASPM when the NIC traffic has
> > more than 10 packets, and vice versa. The possible reason for this is
> > likely because the buffer on the chip is too small for its ASPM exit
> > latency.
> >
> > Realtek confirmed that all their PCIe LAN NICs, r8106, r8168 and r8125
> > use dynamic ASPM under Windows. So implement the same mechanism here to
> > resolve the issue.
> >
> > Because ASPM control may not be granted by BIOS while ASPM is enabled,
> > remove aspm_manageable and use pcie_aspm_capable() instead. If BIOS
> > enables ASPM for the device, we want to enable dynamic ASPM on it.
> >
> > In addition, since PCIe ASPM can be switched via sysfs, enable/disable
> > dynamic ASPM accordingly by checking pcie_aspm_enabled().
> >
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> > ---
> > v4:
> >  - Squash two patches
> >  - Remove aspm_manageable and use pcie_aspm_capable()
> >    pcie_aspm_enabled() accordingly
> >
> > v3:
> >  - Use msecs_to_jiffies() for delay time
> >  - Use atomic_t instead of mutex for bh
> >  - Mention the buffer size and ASPM exit latency in commit message
> >
> > v2:
> >  - Use delayed_work instead of timer_list to avoid interrupt context
> >  - Use mutex to serialize packet counter read/write
> >  - Wording change
> >  drivers/net/ethernet/realtek/r8169_main.c | 77 ++++++++++++++++++++---
> >  1 file changed, 69 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> > index 46a6ff9a782d7..97dba8f437b78 100644
> > --- a/drivers/net/ethernet/realtek/r8169_main.c
> > +++ b/drivers/net/ethernet/realtek/r8169_main.c
> > @@ -623,7 +623,10 @@ struct rtl8169_private {
> >       } wk;
> >
> >       unsigned supports_gmii:1;
> > -     unsigned aspm_manageable:1;
> > +     unsigned rtl_aspm_enabled:1;
> > +     struct delayed_work aspm_toggle;
> > +     atomic_t aspm_packet_count;
> > +
> >       dma_addr_t counters_phys_addr;
> >       struct rtl8169_counters *counters;
> >       struct rtl8169_tc_offsets tc_offset;
> > @@ -698,6 +701,20 @@ static bool rtl_is_8168evl_up(struct rtl8169_private *tp)
> >              tp->mac_version <= RTL_GIGA_MAC_VER_53;
> >  }
> >
> > +static int rtl_supports_aspm(struct rtl8169_private *tp)
> > +{
> > +     switch (tp->mac_version) {
> > +     case RTL_GIGA_MAC_VER_02 ... RTL_GIGA_MAC_VER_31:
> > +     case RTL_GIGA_MAC_VER_37:
> > +     case RTL_GIGA_MAC_VER_39:
> > +     case RTL_GIGA_MAC_VER_43:
> > +     case RTL_GIGA_MAC_VER_47:
> > +             return 0;
> > +     default:
> > +             return 1;
> > +     }
>
> Why is this needed now that you have pcie_aspm_capable()?

The black list is copied from vendor driver.
Will remove it in next iteration and hopefully pcie_aspm_capable() is
sufficient.

>
> > +}
> > +
> >  static bool rtl_supports_eee(struct rtl8169_private *tp)
> >  {
> >       return tp->mac_version >= RTL_GIGA_MAC_VER_34 &&
> > @@ -2699,8 +2716,15 @@ static void rtl_enable_exit_l1(struct rtl8169_private *tp)
> >
> >  static void rtl_hw_aspm_clkreq_enable(struct rtl8169_private *tp, bool enable)
> >  {
> > +     struct pci_dev *pdev = tp->pci_dev;
> > +
> > +     if (!pcie_aspm_enabled(pdev) && enable)
> > +             return;
> > +
> > +     tp->rtl_aspm_enabled = enable;
> > +
> >       /* Don't enable ASPM in the chip if OS can't control ASPM */
> > -     if (enable && tp->aspm_manageable) {
> > +     if (enable) {
> >               RTL_W8(tp, Config5, RTL_R8(tp, Config5) | ASPM_en);
> >               RTL_W8(tp, Config2, RTL_R8(tp, Config2) | ClkReqEn);
> >       } else {
> > @@ -4440,6 +4464,7 @@ static void rtl_tx(struct net_device *dev, struct rtl8169_private *tp,
> >
> >       dirty_tx = tp->dirty_tx;
> >
> > +     atomic_add(tp->cur_tx - dirty_tx, &tp->aspm_packet_count);
> >       while (READ_ONCE(tp->cur_tx) != dirty_tx) {
> >               unsigned int entry = dirty_tx % NUM_TX_DESC;
> >               u32 status;
> > @@ -4584,6 +4609,8 @@ static int rtl_rx(struct net_device *dev, struct rtl8169_private *tp, int budget
> >               rtl8169_mark_to_asic(desc);
> >       }
> >
> > +     atomic_add(count, &tp->aspm_packet_count);
> > +
> >       return count;
> >  }
> >
> > @@ -4691,8 +4718,39 @@ static int r8169_phy_connect(struct rtl8169_private *tp)
> >       return 0;
> >  }
> >
> > +#define ASPM_PACKET_THRESHOLD 10
> > +#define ASPM_TOGGLE_INTERVAL 1000
> > +
> > +static void rtl8169_aspm_toggle(struct work_struct *work)
> > +{
> > +     struct rtl8169_private *tp = container_of(work, struct rtl8169_private,
> > +                                               aspm_toggle.work);
> > +     int packet_count;
> > +     bool enable;
> > +
> > +     packet_count = atomic_xchg(&tp->aspm_packet_count, 0);
> > +
> > +     if (pcie_aspm_enabled(tp->pci_dev)) {
> > +             enable = packet_count <= ASPM_PACKET_THRESHOLD;
> > +
> > +             if (tp->rtl_aspm_enabled != enable) {
> > +                     rtl_unlock_config_regs(tp);
>
> This looks racy. Another unlock_config_regs/do_something/lock_config_regs
> can run in parallel. And if such a parallel lock_config_regs is executed
> exactly here, then rtl_hw_aspm_clkreq_enable() may fail.

Yes this is racy.
Will add a lock to prevent the race.

Kai-Heng

>
> > +                     rtl_hw_aspm_clkreq_enable(tp, enable);
> > +                     rtl_lock_config_regs(tp);
> > +             }
> > +     } else if (tp->rtl_aspm_enabled) {
> > +             rtl_unlock_config_regs(tp);
> > +             rtl_hw_aspm_clkreq_enable(tp, false);
> > +             rtl_lock_config_regs(tp);
> > +     }
> > +
> > +     schedule_delayed_work(&tp->aspm_toggle, msecs_to_jiffies(ASPM_TOGGLE_INTERVAL));
> > +}
> > +
> >  static void rtl8169_down(struct rtl8169_private *tp)
> >  {
> > +     cancel_delayed_work_sync(&tp->aspm_toggle);
> > +
> >       /* Clear all task flags */
> >       bitmap_zero(tp->wk.flags, RTL_FLAG_MAX);
> >
> > @@ -4719,6 +4777,11 @@ static void rtl8169_up(struct rtl8169_private *tp)
> >       rtl_reset_work(tp);
> >
> >       phy_start(tp->phydev);
> > +
> > +     /* pcie_aspm_capable may change after system resume */
> > +     if (pcie_aspm_support_enabled() && pcie_aspm_capable(tp->pci_dev) &&
> > +         rtl_supports_aspm(tp))
> > +             schedule_delayed_work(&tp->aspm_toggle, 0);
> >  }
> >
> >  static int rtl8169_close(struct net_device *dev)
> > @@ -5306,12 +5369,6 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
> >       if (rc)
> >               return rc;
> >
> > -     /* Disable ASPM L1 as that cause random device stop working
> > -      * problems as well as full system hangs for some PCIe devices users.
> > -      */
> > -     rc = pci_disable_link_state(pdev, PCIE_LINK_STATE_L1);
> > -     tp->aspm_manageable = !rc;
> > -
> >       /* enable device (incl. PCI PM wakeup and hotplug setup) */
> >       rc = pcim_enable_device(pdev);
> >       if (rc < 0) {
> > @@ -5378,6 +5435,10 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
> >
> >       INIT_WORK(&tp->wk.work, rtl_task);
> >
> > +     INIT_DELAYED_WORK(&tp->aspm_toggle, rtl8169_aspm_toggle);
> > +
> > +     atomic_set(&tp->aspm_packet_count, 0);
> > +
> >       rtl_init_mac_address(tp);
> >
> >       dev->ethtool_ops = &rtl8169_ethtool_ops;
> >
>