netdev - Re: [PATCH v8 RESEND 6/6] r8169: Disable ASPM while doing NAPI poll

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Date:   Tue, 21 Feb 2023 12:08:54 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>, nic_swsd@...ltek.com,
        bhelgaas@...gle.com
Cc:     koba.ko@...onical.com, acelan.kao@...onical.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, sathyanarayanan.kuppuswamy@...ux.intel.com,
        vidyas@...dia.com, rafael.j.wysocki@...el.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH v8 RESEND 6/6] r8169: Disable ASPM while doing NAPI poll

On 21.02.2023 03:38, Kai-Heng Feng wrote:
> NAPI poll of Realtek NICs don't seem to perform well ASPM is enabled.
> The vendor driver uses a mechanism called "dynamic ASPM" to toggle ASPM
> based on the packet number in given time period.
> 
> Instead of implementing "dynamic ASPM", use a more straightforward way
> by disabling ASPM during NAPI poll, as a similar approach was
> implemented to solve slow performance on Realtek wireless NIC, see
> commit 24f5e38a13b5 ("rtw88: Disable PCIe ASPM while doing NAPI poll on
> 8821CE").
> 
> Since NAPI poll should be handled as fast as possible, also remove the
> delay in rtl_hw_aspm_clkreq_enable() which was added by commit
> 94235460f9ea ("r8169: Align ASPM/CLKREQ setting function with vendor
> driver").
> 
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> ---
> v8:
>  - New patch.
> 
>  drivers/net/ethernet/realtek/r8169_main.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> index 897f90b48bba6..4d4a802346ae3 100644
> --- a/drivers/net/ethernet/realtek/r8169_main.c
> +++ b/drivers/net/ethernet/realtek/r8169_main.c
> @@ -2711,8 +2711,6 @@ static void rtl_hw_aspm_clkreq_enable(struct rtl8169_private *tp, bool enable)
>  		RTL_W8(tp, Config2, RTL_R8(tp, Config2) & ~ClkReqEn);
>  		RTL_W8(tp, Config5, RTL_R8(tp, Config5) & ~ASPM_en);
>  	}
> -
> -	udelay(10);
>  }
>  
>  static void rtl_set_fifo_size(struct rtl8169_private *tp, u16 rx_stat,
> @@ -4577,6 +4575,12 @@ static int rtl8169_poll(struct napi_struct *napi, int budget)
>  	struct net_device *dev = tp->dev;
>  	int work_done;
>  
> +	if (tp->aspm_manageable) {
> +		rtl_unlock_config_regs(tp);

NAPI poll runs in softirq context (except for threaded NAPI).
Therefore you should use a spinlock instead of a mutex.

> +		rtl_hw_aspm_clkreq_enable(tp, false);
> +		rtl_lock_config_regs(tp);
> +	}
> +
>  	rtl_tx(dev, tp, budget);
>  
>  	work_done = rtl_rx(dev, tp, budget);
> @@ -4584,6 +4588,12 @@ static int rtl8169_poll(struct napi_struct *napi, int budget)
>  	if (work_done < budget && napi_complete_done(napi, work_done))
>  		rtl_irq_enable(tp);
>  
> +	if (tp->aspm_manageable) {
> +		rtl_unlock_config_regs(tp);
> +		rtl_hw_aspm_clkreq_enable(tp, true);
> +		rtl_lock_config_regs(tp);

Why not moving lock/unlock into rtl_hw_aspm_clkreq_enable()?

> +	}
> +
>  	return work_done;
>  }
>