Re: [PATCH V1] PCI: designware-ep: Fix DBI access before core init

[Vidya Sagar <vidyas@nvidia.com>]

On 7/7/2022 9:30 PM, Bjorn Helgaas wrote:
> External email: Use caution opening links or attachments
> 
> 
> [+cc Serge]
> 
> On Thu, Jul 07, 2022 at 02:39:08PM +0530, Vidya Sagar wrote:
>> Hi,
>> Anyone has review comments for this change?
>> Without this change, Tegra194's endpoint mode is effectively broken.
> 
> Did Tegra194 endpoint mode ever work, or has this always been broken.
> Wondering if there's a Fixes: or stable tag we should add.  Also cc'd
> Serge since he's been doing similar work on dwc.

Yes. The endpoint mode of Tegra194 did work particularly after the 
commit ac37dde72177 ("PCI: dwc: Add API to notify core initialization 
completion")
There are many changes that got merged after this and hence couldn't 
really point to one change to quote in Fixes: tag.

Thanks & Regards,
Vidya Sagar

> 
>> On 6/22/2022 9:31 AM, Vidya Sagar wrote:
>>> Platforms that cannot support their core initialization without the
>>> reference clock from the host, implement the feature 'core_init_notifier'
>>> to indicate the DesignWare sub-system about when their core is getting
>>> initialized. Any accesses to the core (Ex:- DBI) would result in system
>>> hang in such systems (Ex:- tegra194). This patch moves any access to the
>>> core to dw_pcie_ep_init_complete() API which is effectively called only
>>> after the core initialization.
>>>
>>> Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
>>> ---
>>>    .../pci/controller/dwc/pcie-designware-ep.c   | 88 +++++++++++--------
>>>    1 file changed, 49 insertions(+), 39 deletions(-)
>>>
>>> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
>>> index 0eda8236c125..9feec720175f 100644
>>> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
>>> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
>>> @@ -639,9 +639,14 @@ 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;
>>> +   struct pci_epc *epc = ep->epc;
>>>      unsigned int offset;
>>>      unsigned int nbars;
>>>      u8 hdr_type;
>>> +   u8 func_no;
>>> +   void *addr;
>>>      u32 reg;
>>>      int i;
>>> @@ -654,6 +659,42 @@ int dw_pcie_ep_init_complete(struct dw_pcie_ep *ep)
>>>              return -EIO;
>>>      }
>>> +   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 < 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);
>>> +   }
>>> +
>>>      offset = dw_pcie_ep_find_ext_capability(pci, PCI_EXT_CAP_ID_REBAR);
>>>      dw_pcie_dbi_ro_wr_en(pci);
>>> @@ -677,8 +718,6 @@ 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);
>>> @@ -686,7 +725,6 @@ 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);
>>> @@ -708,8 +746,6 @@ 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;
>>> @@ -717,26 +753,6 @@ 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);
>>> @@ -753,20 +769,6 @@ 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);
>>> @@ -790,6 +792,14 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>>>                      return 0;
>>>      }
>>> +   /*
>>> +    * NOTE:- Avoid accessing the hardware (Ex:- DBI space) before this
>>> +    * step as platforms that implement 'core_init_notifier' feature may
>>> +    * not have the hardware ready (i.e. core initialized) for access
>>> +    * (Ex: tegra194). Any hardware access on such platforms result
>>> +    * in system hard hang.
>>> +    */
>>> +
>>>      return dw_pcie_ep_init_complete(ep);
>>>    }
>>>    EXPORT_SYMBOL_GPL(dw_pcie_ep_init);
>>>