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To:     Kai-Heng Feng <kai.heng.feng@canonical.com>, nic_swsd@realtek.com
Cc:     "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        "open list:8169 10/100/1000 GIGABIT ETHERNET DRIVER" 
        <netdev@vger.kernel.org>, open list <linux-kernel@vger.kernel.org>
References: <20210812155341.817031-1-kai.heng.feng@canonical.com>
From:   Heiner Kallweit <hkallweit1@gmail.com>
Subject: Re: [PATCH v2 1/2] r8169: Implement dynamic ASPM mechanism
Message-ID: <631a47b7-f068-7770-65f4-bdfedc4b7d6c@gmail.com>
Date:   Fri, 13 Aug 2021 08:48:56 +0200
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On 12.08.2021 17:53, 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.
> 
> Realtek confirmed that all their PCIe LAN NICs, r8106, r8168 and r8125

As we have Realtek in this mail thread:
Typically hw issues affect 1-3 chip versions only. The ASPM problems seem
to have been existing for at least 15 years now, in every chip version.
It seems that even the new RTL8125 chip generation still has broken ASPM.
Why was this never fixed? ASPM not considered to be relevant? HW design
too broken?

> use dynamic ASPM under Windows. So implement the same mechanism here to
> resolve the issue.
> 
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> ---
> 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 | 45 +++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
> 
> diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> index c7af5bc3b8af..7ab2e841dc69 100644
> --- a/drivers/net/ethernet/realtek/r8169_main.c
> +++ b/drivers/net/ethernet/realtek/r8169_main.c
> @@ -624,6 +624,11 @@ struct rtl8169_private {
>  
>  	unsigned supports_gmii:1;
>  	unsigned aspm_manageable:1;
> +	unsigned aspm_enabled:1;
> +	struct delayed_work aspm_toggle;
> +	struct mutex aspm_mutex;
> +	u32 aspm_packet_count;
> +
>  	dma_addr_t counters_phys_addr;
>  	struct rtl8169_counters *counters;
>  	struct rtl8169_tc_offsets tc_offset;
> @@ -2671,6 +2676,8 @@ static void rtl_hw_aspm_clkreq_enable(struct rtl8169_private *tp, bool enable)
>  		RTL_W8(tp, Config5, RTL_R8(tp, Config5) & ~ASPM_en);
>  	}
>  
> +	tp->aspm_enabled = enable;
> +
>  	udelay(10);
>  }
>  
> @@ -4408,6 +4415,9 @@ static void rtl_tx(struct net_device *dev, struct rtl8169_private *tp,
>  
>  	dirty_tx = tp->dirty_tx;
>  
> +	mutex_lock(&tp->aspm_mutex);
> +	tp->aspm_packet_count += tp->cur_tx - dirty_tx;
> +	mutex_unlock(&tp->aspm_mutex);
>  	while (READ_ONCE(tp->cur_tx) != dirty_tx) {
>  		unsigned int entry = dirty_tx % NUM_TX_DESC;
>  		u32 status;
> @@ -4552,6 +4562,10 @@ static int rtl_rx(struct net_device *dev, struct rtl8169_private *tp, int budget
>  		rtl8169_mark_to_asic(desc);
>  	}
>  
> +	mutex_lock(&tp->aspm_mutex);
> +	tp->aspm_packet_count += count;
> +	mutex_unlock(&tp->aspm_mutex);
> +
>  	return count;
>  }
>  
> @@ -4659,8 +4673,33 @@ 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);
> +	bool enable;
> +
> +	mutex_lock(&tp->aspm_mutex);
> +	enable = tp->aspm_packet_count <= ASPM_PACKET_THRESHOLD;
> +	tp->aspm_packet_count = 0;
> +	mutex_unlock(&tp->aspm_mutex);
> +
> +	if (tp->aspm_enabled != enable) {
> +		rtl_unlock_config_regs(tp);
> +		rtl_hw_aspm_clkreq_enable(tp, enable);
> +		rtl_lock_config_regs(tp);
> +	}
> +
> +	schedule_delayed_work(&tp->aspm_toggle, 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);
>  
> @@ -4687,6 +4726,8 @@ static void rtl8169_up(struct rtl8169_private *tp)
>  	rtl_reset_work(tp);
>  
>  	phy_start(tp->phydev);
> +
> +	schedule_delayed_work(&tp->aspm_toggle, ASPM_TOGGLE_INTERVAL);
>  }
>  
>  static int rtl8169_close(struct net_device *dev)
> @@ -5347,6 +5388,10 @@ 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);
> +
> +	mutex_init(&tp->aspm_mutex);
> +
>  	rtl_init_mac_address(tp);
>  
>  	dev->ethtool_ops = &rtl8169_ethtool_ops;
>