linux-kernel - Re: [PATCH] PCI: dwc: fix crash seen due to missing ops

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Date:   Wed, 22 Mar 2017 15:47:06 +0000
From:   Joao Pinto <Joao.Pinto@...opsys.com>
To:     Niklas Cassel <niklas.cassel@...s.com>, <bhelgaas@...gle.com>,
        <jingoohan1@...il.com>, <Joao.Pinto@...opsys.com>, <kishon@...com>
CC:     <linux-arm-kernel@...s.com>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Niklas Cassel <niklass@...s.com>
Subject: Re: [PATCH] PCI: dwc: fix crash seen due to missing ops


Hi Niklas,

Às 2:43 PM de 3/21/2017, Niklas Cassel escreveu:
> From: Niklas Cassel <niklas.cassel@...s.com>
> 
> Fix the following crash, seen in dwc/pcie-artpec6.
> 
>   Unable to handle kernel NULL pointer dereference at virtual address 00000004
>   pgd = c0204000
>   [00000004] *pgd=00000000
>   Internal error: Oops: 5 [#1] SMP ARM
>   Modules linked in:
>   CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.11.0-rc3-next-20170321 #1
>   Hardware name: Axis ARTPEC-6 Platform
>   task: db098000 task.stack: db096000
>   PC is at dw_pcie_writel_dbi+0x2c/0xd0
>   ...
> 
> While at it, fix the same problem for pcie-designware-plat.
> 
> Fixes: 442ec4c04d12 ("PCI: dwc: all: Split struct pcie_port into host-only and core structures")
> Signed-off-by: Niklas Cassel <niklas.cassel@...s.com>
> ---
>  drivers/pci/dwc/pcie-artpec6.c         | 4 ++++
>  drivers/pci/dwc/pcie-designware-plat.c | 4 ++++
>  2 files changed, 8 insertions(+)
> 
> diff --git a/drivers/pci/dwc/pcie-artpec6.c b/drivers/pci/dwc/pcie-artpec6.c
> index fcd3ef845883..6d23683c0892 100644
> --- a/drivers/pci/dwc/pcie-artpec6.c
> +++ b/drivers/pci/dwc/pcie-artpec6.c
> @@ -234,6 +234,9 @@ static int artpec6_add_pcie_port(struct artpec6_pcie *artpec6_pcie,
>  	return 0;
>  }
>  
> +static const struct dw_pcie_ops dw_pcie_ops = {
> +};
> +
>  static int artpec6_pcie_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
> @@ -252,6 +255,7 @@ static int artpec6_pcie_probe(struct platform_device *pdev)
>  		return -ENOMEM;
>  
>  	pci->dev = dev;
> +	pci->ops = &dw_pcie_ops;
>  
>  	artpec6_pcie->pci = pci;
>  
> diff --git a/drivers/pci/dwc/pcie-designware-plat.c b/drivers/pci/dwc/pcie-designware-plat.c
> index b6c832ba39dd..f20d494922ab 100644
> --- a/drivers/pci/dwc/pcie-designware-plat.c
> +++ b/drivers/pci/dwc/pcie-designware-plat.c
> @@ -86,6 +86,9 @@ static int dw_plat_add_pcie_port(struct pcie_port *pp,
>  	return 0;
>  }
>  
> +static const struct dw_pcie_ops dw_pcie_ops = {
> +};
> +
>  static int dw_plat_pcie_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
> @@ -103,6 +106,7 @@ static int dw_plat_pcie_probe(struct platform_device *pdev)
>  		return -ENOMEM;
>  
>  	pci->dev = dev;
> +	pci->ops = &dw_pcie_ops;
>  
>  	dw_plat_pcie->pci = pci;
>  
> 

In the case of pcie-designware-plat you have the declaration of pci->ops:
https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/tree/drivers/pci/dwc/pcie-designware-plat.c#n78

and in artpec6 in here:
https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/tree/drivers/pci/dwc/pcie-artpec6.c#n226

Both declarations are made previously of calling dw_pcie_host_init(), so why do
you need this dummy ops in the probe function? I never had that necessity.

Thanks,
Joao

Thanks,