Tony Chuang <yhchuang@xxxxxxxxxxx> 於 2019年8月16日 週五 下午4:07寫道： > > Hi, > > A few more questions below > > > > From: Jian-Hong Pan [mailto:jian-hong@xxxxxxxxxxxx] > > > > > > 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@xxxxxxxxxxxx> > > > --- > > > 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? Ah! You are right! The interrupts are already disabled in the interrupt handler. So, there is no need to disable more once. I can tweak it. > > > 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? I got this idea "Avoid back to back interrupt" from Intel WiFi's driver. https://elixir.bootlin.com/linux/v5.3-rc4/source/drivers/net/wireless/intel/iwlwifi/pcie/rx.c#L2071 So, I disable rtw_pci interrupt here in first half IRQ. (Re-enable in bottom half) > > > > +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); Then, re-enable rtw_pci interrupt here in bottom half of the IRQ. Here is the place where Intel WiFi re-enable interrupts. https://elixir.bootlin.com/linux/v5.3-rc4/source/drivers/net/wireless/intel/iwlwifi/pcie/rx.c#L1959 Now, we can go back to the question "Shouldn't we protect the ISRs above?" 1. What does the lock: rtwpci->irq_lock protect for? According to the code, seems only rtw_pci interrupt's state which is enabled or not. 2. How about the ISRs you mentioned? This part will only be executed if there is a fresh rtw_pci interrupt. The first half already disabled rtw_pci interrupt, so there is no more fresh rtw_pci interrupt until rtw_pci interrupt is enabled again. Therefor, the rtwpci->irq_lock only wraps the rtw_pci interrupt enablement. If there is any more entry that I missed and will interfere, please let me know. Thank you Jian-Hong Pan
