linux-kernel - Re: [PATCH v2 2/2] PCI: qcom: Restrict pci transactions after pci suspend

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Message-ID: <20220704045415.GC6560@thinkpad>
Date:   Mon, 4 Jul 2022 10:24:15 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc:     helgaas@...nel.org, linux-pci@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_vbadigan@...cinc.com, quic_hemantk@...cinc.com,
        quic_nitegupt@...cinc.com, quic_skananth@...cinc.com,
        quic_ramkri@...cinc.com, swboyd@...omium.org,
        dmitry.baryshkov@...aro.org, Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stanimir Varbanov <svarbanov@...sol.com>
Subject: Re: [PATCH v2 2/2] PCI: qcom: Restrict pci transactions after pci
 suspend

On Wed, Jun 29, 2022 at 03:03:34PM +0530, Krishna chaitanya chundru wrote:
> If the endpoint device state is D0 and irq's are not freed, then
> kernel try to mask interrupts by writing in to the vector
> table (for MSIX interrupts) and config space (for MSI's).
> 
> These transactions are initiated after clocks are getting disabled
> as part of PM suspend call. Due to it, these transactions are
> resulting in un-clocked access and eventual to crashes.
> 
> So added a logic in qcom driver to restrict the unclocked access.
> And updated the logic to check the link state before masking
> or unmasking the interrupts.
> 

No other PCI driver is doing the DBI access restriction. So this makes me feel
that the fix is somewhere else.

I'll dig into it and come back.

Thanks,
Mani

> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware-host.c | 14 +++++++--
>  drivers/pci/controller/dwc/pcie-qcom.c            | 35 +++++++++++++++++++++--
>  2 files changed, 45 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 2fa86f3..2a46b40 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -29,13 +29,23 @@ static void dw_msi_ack_irq(struct irq_data *d)
>  
>  static void dw_msi_mask_irq(struct irq_data *d)
>  {
> -	pci_msi_mask_irq(d);
> +	struct pcie_port *pp = irq_data_get_irq_chip_data(d->parent_data);
> +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> +
> +	if (dw_pcie_link_up(pci))
> +		pci_msi_mask_irq(d);
> +
>  	irq_chip_mask_parent(d);
>  }
>  
>  static void dw_msi_unmask_irq(struct irq_data *d)
>  {
> -	pci_msi_unmask_irq(d);
> +	struct pcie_port *pp = irq_data_get_irq_chip_data(d->parent_data);
> +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> +
> +	if (dw_pcie_link_up(pci))
> +		pci_msi_unmask_irq(d);
> +
>  	irq_chip_unmask_parent(d);
>  }
>  
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 8e9ef37..227bc24a 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -1331,12 +1331,41 @@ static int qcom_pcie_disable_clks_2_7_0(struct qcom_pcie *pcie)
>  	return 0;
>  }
>  
> +static u32 qcom_pcie_read_dbi(struct dw_pcie *pci, void __iomem *base,
> +				u32 reg, size_t size)
> +{
> +	struct qcom_pcie *pcie = to_qcom_pcie(pci);
> +	u32 val;
> +
> +	if (pcie->is_suspended)
> +		return PCIBIOS_BAD_REGISTER_NUMBER;
> +
> +	dw_pcie_read(base + reg, size, &val);
> +	return val;
> +}
> +
> +static void qcom_pcie_write_dbi(struct dw_pcie *pci, void __iomem *base,
> +					u32 reg, size_t size, u32 val)
> +{
> +	struct qcom_pcie *pcie = to_qcom_pcie(pci);
> +
> +	if (pcie->is_suspended)
> +		return;
> +
> +	dw_pcie_write(base + reg, size, val);
> +}
>  
>  static int qcom_pcie_link_up(struct dw_pcie *pci)
>  {
> -	u16 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> -	u16 val = readw(pci->dbi_base + offset + PCI_EXP_LNKSTA);
> +	struct qcom_pcie *pcie = to_qcom_pcie(pci);
> +	u16 offset;
> +	u16 val;
> +
> +	if (pcie->is_suspended)
> +		return false;
>  
> +	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> +	val = readw(pci->dbi_base + offset + PCI_EXP_LNKSTA);
>  	return !!(val & PCI_EXP_LNKSTA_DLLLA);
>  }
>  
> @@ -1580,6 +1609,8 @@ static const struct qcom_pcie_cfg sc7280_cfg = {
>  static const struct dw_pcie_ops dw_pcie_ops = {
>  	.link_up = qcom_pcie_link_up,
>  	.start_link = qcom_pcie_start_link,
> +	.read_dbi = qcom_pcie_read_dbi,
> +	.write_dbi = qcom_pcie_write_dbi,
>  };
>  
>  static int qcom_pcie_probe(struct platform_device *pdev)
> -- 
> 2.7.4
> 

-- 
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