netdev - RE: [PATCH] rtw88: pci: Move a mass of jobs in hw IRQ to soft IRQ

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Date:   Fri, 16 Aug 2019 08:06:59 +0000
From:   Tony Chuang <yhchuang@...ltek.com>
To:     Tony Chuang <yhchuang@...ltek.com>,
        Jian-Hong Pan <jian-hong@...lessm.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S . Miller" <davem@...emloft.net>
CC:     "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux@...lessm.com" <linux@...lessm.com>
Subject: RE: [PATCH] rtw88: pci: Move a mass of jobs in hw IRQ to soft IRQ

Hi,

A few more questions below

> > From: Jian-Hong Pan [mailto:jian-hong@...lessm.com]
> >
> > There is a mass of jobs between spin lock and unlock in the hardware
> > IRQ which will occupy much time originally. To make system work more
> > efficiently, this patch moves the jobs to the soft IRQ (bottom half) to
> > reduce the time in hardware IRQ.
> >
> > Signed-off-by: Jian-Hong Pan <jian-hong@...lessm.com>
> > ---
> >  drivers/net/wireless/realtek/rtw88/pci.c | 36 +++++++++++++++++++-----
> >  1 file changed, 29 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/net/wireless/realtek/rtw88/pci.c
> > b/drivers/net/wireless/realtek/rtw88/pci.c
> > index 00ef229552d5..355606b167c6 100644
> > --- a/drivers/net/wireless/realtek/rtw88/pci.c
> > +++ b/drivers/net/wireless/realtek/rtw88/pci.c
> > @@ -866,12 +866,29 @@ static irqreturn_t rtw_pci_interrupt_handler(int
> irq,
> > void *dev)
> >  {
> >  	struct rtw_dev *rtwdev = dev;
> >  	struct rtw_pci *rtwpci = (struct rtw_pci *)rtwdev->priv;
> > -	u32 irq_status[4];
> > +	unsigned long flags;
> >
> > -	spin_lock(&rtwpci->irq_lock);
> > +	spin_lock_irqsave(&rtwpci->irq_lock, flags);

I think you can use 'spin_lock()' here as it's in IRQ context?

> >  	if (!rtwpci->irq_enabled)
> >  		goto out;
> >
> > +	/* disable RTW PCI interrupt to avoid more interrupts before the end of
> > +	 * thread function
> > +	 */
> > +	rtw_pci_disable_interrupt(rtwdev, rtwpci);


Why do we need rtw_pci_disable_interrupt() here.
Have you done any experiment and decided to add this.
If you have can you share your results to me?


> > +out:
> > +	spin_unlock_irqrestore(&rtwpci->irq_lock, flags);

spin_unlock()

> > +
> > +	return IRQ_WAKE_THREAD;
> > +}
> > +
> > +static irqreturn_t rtw_pci_interrupt_threadfn(int irq, void *dev)
> > +{
> > +	struct rtw_dev *rtwdev = dev;
> > +	struct rtw_pci *rtwpci = (struct rtw_pci *)rtwdev->priv;
> > +	unsigned long flags;
> > +	u32 irq_status[4];
> > +
> >  	rtw_pci_irq_recognized(rtwdev, rtwpci, irq_status);
> >
> >  	if (irq_status[0] & IMR_MGNTDOK)
> > @@ -891,8 +908,11 @@ static irqreturn_t rtw_pci_interrupt_handler(int
> irq,
> > void *dev)
> >  	if (irq_status[0] & IMR_ROK)
> >  		rtw_pci_rx_isr(rtwdev, rtwpci, RTW_RX_QUEUE_MPDU);
> >
> > -out:
> > -	spin_unlock(&rtwpci->irq_lock);
> > +	/* all of the jobs for this interrupt have been done */
> > +	spin_lock_irqsave(&rtwpci->irq_lock, flags);
> 
> Shouldn't we protect the ISRs above?
> 
> This patch could actually reduce the time of IRQ.
> But I think I need to further test it with PCI MSI interrupt.
> https://patchwork.kernel.org/patch/11081539/
> 
> Maybe we could drop the "rtw_pci_[enable/disable]_interrupt" when MSI
> Is enabled with this patch.
> 
> > +	if (rtw_flag_check(rtwdev, RTW_FLAG_RUNNING))
> > +		rtw_pci_enable_interrupt(rtwdev, rtwpci);
> > +	spin_unlock_irqrestore(&rtwpci->irq_lock, flags);
> >
> >  	return IRQ_HANDLED;
> >  }
> > @@ -1152,8 +1172,10 @@ static int rtw_pci_probe(struct pci_dev *pdev,
> >  		goto err_destroy_pci;
> >  	}
> >
> > -	ret = request_irq(pdev->irq, &rtw_pci_interrupt_handler,
> > -			  IRQF_SHARED, KBUILD_MODNAME, rtwdev);
> > +	ret = devm_request_threaded_irq(rtwdev->dev, pdev->irq,
> > +					rtw_pci_interrupt_handler,
> > +					rtw_pci_interrupt_threadfn,
> > +					IRQF_SHARED, KBUILD_MODNAME, rtwdev);
> >  	if (ret) {
> >  		ieee80211_unregister_hw(hw);
> >  		goto err_destroy_pci;
> > @@ -1192,7 +1214,7 @@ static void rtw_pci_remove(struct pci_dev
> *pdev)
> >  	rtw_pci_disable_interrupt(rtwdev, rtwpci);
> >  	rtw_pci_destroy(rtwdev, pdev);
> >  	rtw_pci_declaim(rtwdev, pdev);
> > -	free_irq(rtwpci->pdev->irq, rtwdev);
> > +	devm_free_irq(rtwdev->dev, rtwpci->pdev->irq, rtwdev);
> >  	rtw_core_deinit(rtwdev);
> >  	ieee80211_free_hw(hw);
> >  }
> > --
> > 2.20.1
> 
> Yan-Hsuan
> 

Thanks
Yan-Hsuan