linux-kernel - Re: [PATCH v3 2/5] PCI: tegra194: Move dw_pcie_ep

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Date:   Tue, 25 Oct 2022 20:02:07 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Vidya Sagar <vidyas@...dia.com>
Cc:     kishon@...nel.org, lpieralisi@...nel.org, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        kw@...ux.com, robh@...nel.org, vigneshr@...com
Subject: Re: [PATCH v3 2/5] PCI: tegra194: Move dw_pcie_ep_linkup() to
 threaded IRQ handler

Hi Vidya,

On Mon, Oct 10, 2022 at 07:53:52PM +0530, Vidya Sagar wrote:
> Hi Mani,
> Thanks for your change. One comment though.
> 
> On 10/6/2022 7:19 PM, Manivannan Sadhasivam wrote:
> > External email: Use caution opening links or attachments
> > 
> > 
> > dw_pcie_ep_linkup() may take more time to execute depending on the EPF
> > driver implementation. Calling this API in the hard IRQ handler is not
> > encouraged since the hard IRQ handlers are supposed to complete quickly.
> > 
> > So move the dw_pcie_ep_linkup() call to threaded IRQ handler.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >   drivers/pci/controller/dwc/pcie-tegra194.c | 8 ++++++--
> >   1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
> > index 1b6b437823d2..6a487f52e1fb 100644
> > --- a/drivers/pci/controller/dwc/pcie-tegra194.c
> > +++ b/drivers/pci/controller/dwc/pcie-tegra194.c
> > @@ -287,6 +287,7 @@ struct tegra_pcie_dw {
> >          struct gpio_desc *pex_refclk_sel_gpiod;
> >          unsigned int pex_rst_irq;
> >          int ep_state;
> > +       long link_status;
> >   };
> > 
> >   static inline struct tegra_pcie_dw *to_tegra_pcie(struct dw_pcie *pci)
> > @@ -450,9 +451,13 @@ static void pex_ep_event_hot_rst_done(struct tegra_pcie_dw *pcie)
> >   static irqreturn_t tegra_pcie_ep_irq_thread(int irq, void *arg)
> >   {
> >          struct tegra_pcie_dw *pcie = arg;
> > +       struct dw_pcie_ep *ep = &pcie->pci.ep;
> >          struct dw_pcie *pci = &pcie->pci;
> >          u32 val, speed;
> > 
> > +       if (test_and_clear_bit(0, &pcie->link_status))
> > +               dw_pcie_ep_linkup(ep);
> > +
> >          speed = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_LNKSTA) &
> >                  PCI_EXP_LNKSTA_CLS;
> >          clk_set_rate(pcie->core_clk, pcie_gen_freq[speed - 1]);
> > @@ -499,7 +504,6 @@ static irqreturn_t tegra_pcie_ep_irq_thread(int irq, void *arg)
> >   static irqreturn_t tegra_pcie_ep_hard_irq(int irq, void *arg)
> >   {
> >          struct tegra_pcie_dw *pcie = arg;
> > -       struct dw_pcie_ep *ep = &pcie->pci.ep;
> >          int spurious = 1;
> >          u32 status_l0, status_l1, link_status;
> > 
> > @@ -515,7 +519,7 @@ static irqreturn_t tegra_pcie_ep_hard_irq(int irq, void *arg)
> >                          link_status = appl_readl(pcie, APPL_LINK_STATUS);
> >                          if (link_status & APPL_LINK_STATUS_RDLH_LINK_UP) {
> >                                  dev_dbg(pcie->dev, "Link is up with Host\n");
> > -                               dw_pcie_ep_linkup(ep);
> > +                               set_bit(0, &pcie->link_status);
> 
> irq thread needs to be woken up at this point. So, please add
> return IRQ_WAKE_THREAD;
> 

Ah, missed that. Will add it in next version.

Thanks,
Mani

> Thanks,
> Vidya Sagar
> 
> >                          }
> >                  }
> > 
> > --
> > 2.25.1
> > 

-- 
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