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

[Kishon Vijay Abraham I <kishon@ti.com>]

Hi Kunihiko,

On 01/09/21 10:46 am, 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().

Ideally pci_epc_create() should be the last step by the controller driver before
handing the control to the core EPC framework. Since after this step the EPC
framework can start invoking the epc_ops.

Here more stuff is being added to dw_pcie_ep_init_complete() which is required
for epc_ops and this could result in aborts for platforms which does not add
core_init_notifier.

Thanks,
Kishon

> 
> Cc: Xiaowei Bao <xiaowei.bao@nxp.com>
> Cc: Vidya Sagar <vidyas@nvidia.com>
> Fixes: 6bfc9c3a2c70 ("PCI: designware-ep: Move the function of getting MSI capability forward")
> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
> Acked-by: Om Prakash Singh <omp@nvidia.com>
> Reviewed-by: Vidya Sagar <vidyas@nvidia.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
> @@ -636,16 +636,56 @@ static unsigned int dw_pcie_ep_find_ext_capability(struct dw_pcie *pci, int cap)
>  int dw_pcie_ep_init_complete(struct dw_pcie_ep *ep)
>  {
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> +	struct dw_pcie_ep_func *ep_func;
> +	struct device *dev = pci->dev;
>  	unsigned int offset;
>  	unsigned int nbars;
>  	u8 hdr_type;
> +	u8 func_no;
> +	void *addr;
>  	u32 reg;
>  	int i;
>  
> +	dw_pcie_iatu_detect(pci);
> +
> +	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;
> +
> +	for (func_no = 0; func_no < ep->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);
> +	}
> +
>  	hdr_type = dw_pcie_readb_dbi(pci, PCI_HEADER_TYPE) &
>  		   PCI_HEADER_TYPE_MASK;
>  	if (hdr_type != PCI_HEADER_TYPE_NORMAL) {
> -		dev_err(pci->dev,
> +		dev_err(dev,
>  			"PCIe controller is not set to EP mode (hdr_type:0x%x)!\n",
>  			hdr_type);
>  		return -EIO;
> @@ -674,8 +714,6 @@ EXPORT_SYMBOL_GPL(dw_pcie_ep_init_complete);
>  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);
>  
>