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

[Bjorn Helgaas]

On Sat, Aug 28, 2021 at 01:14:52AM +0800, 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.

This sounds like good speculation, but of course, it would be better
to have the supporting data.

You say above that this problem affects r8169 on "some platforms."  I
infer that ASPM works fine on other platforms.  It would be extremely
interesting to have some data on both classes, e.g., "lspci -vv"
output for the entire system.

If r8169 ASPM works well on some systems, we *should* be able to make
it work well on *all* systems, because the device can't tell what
system it's in.  All the device can see are the latencies for entry
and exit for link states.

IIUC this patch makes the driver wake up every 1000ms.  If the NIC has
sent or received more than 10 packets in the last 1000ms, it disables
ASPM; otherwise it enables ASPM.

I asked these same questions earlier, but nothing changed, so I won't
raise them again if you don't think they're pertinent.  Some patch
splitting comments below.

> 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@xxxxxxxxxxxxx>
> ---
> 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;
> +	}

This part looks like it should be a separate patch.  I would think
rtl_init_one() could call this once and set a bit in rtl8169_private.
Then rtl_hw_aspm_clkreq_enable() could just return without doing
anything if the bit is not set.

> +}
> +
>  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) {

This part also looks like it should be a separate patch, since it is
strictly concerned with whether the OS can control ASPM and doesn't
seem related to dynamic ASPM.

>  		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);
> +			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;
> -- 
> 2.32.0
>