linux-kernel - Re: [PATCH] PCI: layerscape: Change back to the default error response behavior

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Date:   Wed, 30 Sep 2020 18:59:11 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Zhiqiang Hou <Zhiqiang.Hou@....com>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <lorenzo.pieralisi@....com>, <robh@...nel.org>,
        <bhelgaas@...gle.com>, <minghuan.Lian@....com>
CC:     <roy.zang@....com>, <mingkai.hu@....com>, <leoyang.li@....com>
Subject: Re: [PATCH] PCI: layerscape: Change back to the default error
 response behavior

Hi Hou,

On 29/09/20 6:43 pm, Zhiqiang Hou wrote:
> From: Hou Zhiqiang <Zhiqiang.Hou@....com>
> 
> In the current error response behavior, it will send a SLVERR response
> to device's internal AXI slave system interface when the PCIe controller
> experiences an erroneous completion (UR, CA and CT) from an external
> completer for its outbound non-posted request, which will result in
> SError and crash the kernel directly.
> This patch change back it to the default behavior to increase the
> robustness of the kernel. In the default behavior, it always sends an
> OKAY response to the internal AXI slave interface when the controller
> gets these erroneous completions. And the AER driver will report and
> try to recover these errors.

I don't think not forwarding any error interrupts is a good idea. Maybe
you could disable it while reading configuration space registers
(vendorID and deviceID) and then enable error forwarding back?

Thanks
Kishon
> 
> Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@....com>
> ---
>  drivers/pci/controller/dwc/pci-layerscape.c | 11 -----------
>  1 file changed, 11 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-layerscape.c b/drivers/pci/controller/dwc/pci-layerscape.c
> index f24f79a70d9a..e92ab8a77046 100644
> --- a/drivers/pci/controller/dwc/pci-layerscape.c
> +++ b/drivers/pci/controller/dwc/pci-layerscape.c
> @@ -30,8 +30,6 @@
>  
>  /* PEX Internal Configuration Registers */
>  #define PCIE_STRFMR1		0x71c /* Symbol Timer & Filter Mask Register1 */
> -#define PCIE_ABSERR		0x8d0 /* Bridge Slave Error Response Register */
> -#define PCIE_ABSERR_SETTING	0x9401 /* Forward error of non-posted request */
>  
>  #define PCIE_IATU_NUM		6
>  
> @@ -123,14 +121,6 @@ static int ls_pcie_link_up(struct dw_pcie *pci)
>  	return 1;
>  }
>  
> -/* Forward error response of outbound non-posted requests */
> -static void ls_pcie_fix_error_response(struct ls_pcie *pcie)
> -{
> -	struct dw_pcie *pci = pcie->pci;
> -
> -	iowrite32(PCIE_ABSERR_SETTING, pci->dbi_base + PCIE_ABSERR);
> -}
> -
>  static int ls_pcie_host_init(struct pcie_port *pp)
>  {
>  	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> @@ -142,7 +132,6 @@ static int ls_pcie_host_init(struct pcie_port *pp)
>  	 * dw_pcie_setup_rc() will reconfigure the outbound windows.
>  	 */
>  	ls_pcie_disable_outbound_atus(pcie);
> -	ls_pcie_fix_error_response(pcie);
>  
>  	dw_pcie_dbi_ro_wr_en(pci);
>  	ls_pcie_clear_multifunction(pcie);
>