linux-kernel - Re: [PATCH 5/8] PCI: qcom: Do not advertise hotplug capability for IP v2.3.2

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Message-ID: <20230508102505.GA4190@thinkpad>
Date:   Mon, 8 May 2023 15:55:05 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     lpieralisi@...nel.org, kw@...ux.com, bhelgaas@...gle.com,
        robh@...nel.org, andersson@...nel.org, konrad.dybcio@...aro.org,
        linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, steev@...i.org,
        quic_srichara@...cinc.com
Subject: Re: [PATCH 5/8] PCI: qcom: Do not advertise hotplug capability for
 IP v2.3.2

On Sat, May 06, 2023 at 03:04:42PM +0300, Dmitry Baryshkov wrote:
> On 06/05/2023 10:31, Manivannan Sadhasivam wrote:
> > SoCs making use of Qcom PCIe controller IP v2.3.2 do not support hotplug
> > functionality. But the hotplug capability bit is set by default in the
> > hardware. This causes the kernel PCI core to register hotplug service for
> > the controller and send hotplug commands to it. But those commands will
> > timeout generating messages as below during boot and suspend/resume.
> > 
> > [    5.782159] pcieport 0001:00:00.0: pciehp: Timeout on hotplug command 0x03c0 (issued 2020 msec ago)
> > [    5.810161] pcieport 0001:00:00.0: pciehp: Timeout on hotplug command 0x03c0 (issued 2048 msec ago)
> > [    7.838162] pcieport 0001:00:00.0: pciehp: Timeout on hotplug command 0x07c0 (issued 2020 msec ago)
> > [    7.870159] pcieport 0001:00:00.0: pciehp: Timeout on hotplug command 0x07c0 (issued 2052 msec ago)
> > 
> > This not only spams the console output but also induces a delay of a
> > couple of seconds. To fix this issue, let's clear the HPC bit in
> > PCI_EXP_SLTCAP register as a part of the post init sequence to not
> > advertise the hotplug capability for the controller.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >   drivers/pci/controller/dwc/pcie-qcom.c | 10 ++++++++++
> >   1 file changed, 10 insertions(+)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > index 3d5b3ce9e2da..33353be396ec 100644
> > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > @@ -579,6 +579,8 @@ static int qcom_pcie_init_2_3_2(struct qcom_pcie *pcie)
> >   static int qcom_pcie_post_init_2_3_2(struct qcom_pcie *pcie)
> >   {
> > +	struct dw_pcie *pci = pcie->pci;
> > +	u16 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> >   	u32 val;
> >   	/* enable PCIe clocks and resets */
> > @@ -602,6 +604,14 @@ static int qcom_pcie_post_init_2_3_2(struct qcom_pcie *pcie)
> >   	val |= EN;
> >   	writel(val, pcie->parf + PARF_AXI_MSTR_WR_ADDR_HALT_V2);
> > +	dw_pcie_dbi_ro_wr_en(pci);
> > +
> > +	val = readl(pci->dbi_base + offset + PCI_EXP_SLTCAP);
> > +	val &= ~PCI_EXP_SLTCAP_HPC;
> > +	writel(val, pci->dbi_base + offset + PCI_EXP_SLTCAP);
> > +
> > +	dw_pcie_dbi_ro_wr_dis(pci);
> > +
> 
> Seeing this code again and again makes me wonder if we should have a
> separate function for this.
> 

Makes sense!

- Mani

> -- 
> With best wishes
> Dmitry
> 

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