linux-kernel - Re: [PATCH v2 2/2] PCI: designware-ep: Fix the access to DBI/iATU registers before enabling controller

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Date:   Thu, 10 Feb 2022 16:34:46 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
Cc:     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>,
        Kishon Vijay Abraham I <kishon@...com>,
        Xiaowei Bao <xiaowei.bao@....com>,
        Om Prakash Singh <omp@...dia.com>,
        Vidya Sagar <vidyas@...dia.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] PCI: designware-ep: Fix the access to DBI/iATU
 registers before enabling controller

On Wed, Sep 01, 2021 at 02:16:01PM +0900, Kunihiko Hayashi wrote:
> The driver using core_init_notifier, e.g. pcie-tegra194.c, runs according
> to the following sequence:
> 
>     probe()
>         dw_pcie_ep_init()
> 
>     bind()
>         dw_pcie_ep_start()
>             enable_irq()
> 
>     (interrupt occurred)
>     handler()
>         [enable controller]
>         dw_pcie_ep_init_complete()
>         dw_pcie_ep_init_notify()
> 
> After receiving an interrupt from RC, the handler enables the controller
> and the controller registers can be accessed.
> So accessing the registers should do in dw_pcie_ep_init_complete().
> 
> Currently dw_pcie_ep_init() has functions dw_iatu_detect() and
> dw_pcie_ep_find_capability() that include accesses to DWC registers.
> As a result, accessing the registers before enabling the controller,
> the access will fail.
> 
> The function dw_pcie_ep_init() shouldn't have any access to DWC registers
> if the controller is enabled after calling bind(). This moves access codes
> to DBI/iATU registers and depending variables from dw_pcie_ep_init() to
> dw_pcie_ep_init_complete().
> 
> Cc: Xiaowei Bao <xiaowei.bao@....com>
> Cc: Vidya Sagar <vidyas@...dia.com>
> Fixes: 6bfc9c3a2c70 ("PCI: designware-ep: Move the function of getting MSI capability forward")
> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
> Acked-by: Om Prakash Singh <omp@...dia.com>
> Reviewed-by: Vidya Sagar <vidyas@...dia.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware-ep.c | 81 +++++++++++++------------
>  1 file changed, 41 insertions(+), 40 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index 998b698..00ce83c 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c

[...]

>  int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>  {
>  	int ret;
> -	void *addr;
> -	u8 func_no;
>  	struct resource *res;
>  	struct pci_epc *epc;
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> @@ -683,7 +721,6 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>  	struct platform_device *pdev = to_platform_device(dev);
>  	struct device_node *np = dev->of_node;
>  	const struct pci_epc_features *epc_features;
> -	struct dw_pcie_ep_func *ep_func;
>  
>  	INIT_LIST_HEAD(&ep->func_list);
>  
> @@ -705,8 +742,6 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>  		}
>  	}
>  
> -	dw_pcie_iatu_detect(pci);
> -
>  	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "addr_space");
>  	if (!res)
>  		return -EINVAL;
> @@ -714,26 +749,6 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>  	ep->phys_base = res->start;
>  	ep->addr_size = resource_size(res);
>  
> -	ep->ib_window_map = devm_kcalloc(dev,
> -					 BITS_TO_LONGS(pci->num_ib_windows),
> -					 sizeof(long),
> -					 GFP_KERNEL);
> -	if (!ep->ib_window_map)
> -		return -ENOMEM;
> -
> -	ep->ob_window_map = devm_kcalloc(dev,
> -					 BITS_TO_LONGS(pci->num_ob_windows),
> -					 sizeof(long),
> -					 GFP_KERNEL);
> -	if (!ep->ob_window_map)
> -		return -ENOMEM;
> -
> -	addr = devm_kcalloc(dev, pci->num_ob_windows, sizeof(phys_addr_t),
> -			    GFP_KERNEL);
> -	if (!addr)
> -		return -ENOMEM;
> -	ep->outbound_addr = addr;
> -
>  	if (pci->link_gen < 1)
>  		pci->link_gen = of_pci_get_max_link_speed(np);
>  
> @@ -750,20 +765,6 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>  	if (ret < 0)
>  		epc->max_functions = 1;
>  
> -	for (func_no = 0; func_no < epc->max_functions; func_no++) {
> -		ep_func = devm_kzalloc(dev, sizeof(*ep_func), GFP_KERNEL);
> -		if (!ep_func)
> -			return -ENOMEM;
> -
> -		ep_func->func_no = func_no;
> -		ep_func->msi_cap = dw_pcie_ep_find_capability(ep, func_no,
> -							      PCI_CAP_ID_MSI);
> -		ep_func->msix_cap = dw_pcie_ep_find_capability(ep, func_no,
> -							       PCI_CAP_ID_MSIX);
> -
> -		list_add_tail(&ep_func->list, &ep->func_list);
> -	}
> -
>  	if (ep->ops->ep_init)
>  		ep->ops->ep_init(ep);

You also need to move ep_init() as it can have DBI access too.

Thanks,
Mani

>  
> -- 
> 2.7.4
>