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Date:   Fri, 15 Jul 2022 16:39:58 -0500
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc:     kishon@ti.com, bhelgaas@google.com, robh@kernel.org,
        lorenzo.pieralisi@arm.com, kw@linux.com, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Kunihiko Hayashi <hayashi.kunihiko@socionext.com>,
        Om Prakash Singh <omp@nvidia.com>,
        Vidya Sagar <vidyas@nvidia.com>
Subject: Re: [PATCH] PCI: designware-ep: Move DBI access to init_complete if
 notifier is used
Message-ID: <20220715213958.GA1192967@bhelgaas>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220330060515.22328-1-manivannan.sadhasivam@linaro.org>
Precedence: bulk

On Wed, Mar 30, 2022 at 11:35:15AM +0530, Manivannan Sadhasivam wrote:
> For controllers supporting the CORE_INIT notifier, the resources are
> supposed to be enabled in the init_complete function. Currently,
> these controllers are enabling the resources during probe time due to
> the DBI access happens in dw_pcie_ep_init().
> 
> This creates the dependency with the host PCIe controller since the
> resource enablement like PHY depends on host PCIe to be up. For the
> standalone endpoint usecase, this would never work. So let's move all DBI
> access to init_complete function if CORE_INIT notifier is used. For the
> controllers those doesn't support this notifier, this change is a NO-OP.
> 
> Cc: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
> Cc: Om Prakash Singh <omp@nvidia.com>
> Cc: Vidya Sagar <vidyas@nvidia.com>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> ---
>  .../pci/controller/dwc/pcie-designware-ep.c   | 138 ++++++++++++------
>  drivers/pci/controller/dwc/pcie-designware.h  |   1 +
>  2 files changed, 94 insertions(+), 45 deletions(-)

Sorry this got missed.  Seems like there are two patches to solve the
same problem:

  1) This patch, and
  2) Vidya's patch (https://lore.kernel.org/linux-pci/20220622040133.31058-1-vidyas@nvidia.com/)

I don't know much about dwc or this issue, but if these patches are
functionally equivalent, I think Vidya's is a little more attractive
because:

  - It's smaller (49 insertions(+), 39 deletions(-)).

  - "core_init_notifier" looks like sort of a corner-case feature and
    Vidya's patch doesn't depend on it so it seems more maintainable.

  - It's more straightforward to read -- it basically just moves
    things from dw_pcie_ep_init() to dw_pcie_ep_init_complete(), which
    is exactly the sort of thing I expect if we're doing something out
    of order.

> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index 0eda8236c125..fb2bf4bf5ba0 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -636,6 +636,63 @@ static unsigned int dw_pcie_ep_find_ext_capability(struct dw_pcie *pci, int cap)
>  	return 0;
>  }
>  
> +static int dw_pcie_iatu_config(struct dw_pcie_ep *ep)
> +{
> +	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> +	struct device *dev = pci->dev;
> +	void *addr;
> +
> +	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;
> +
> +	return 0;
> +}
> +
> +static int dw_pcie_ep_func_init(struct dw_pcie_ep *ep)
> +{
> +	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> +	struct dw_pcie_ep_func *ep_func;
> +	struct pci_epc *epc = ep->epc;
> +	struct device *dev = pci->dev;
> +	u8 func_no;
> +
> +	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);
> +	}
> +
> +	return 0;
> +}
> +
>  int dw_pcie_ep_init_complete(struct dw_pcie_ep *ep)
>  {
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> @@ -643,7 +700,22 @@ int dw_pcie_ep_init_complete(struct dw_pcie_ep *ep)
>  	unsigned int nbars;
>  	u8 hdr_type;
>  	u32 reg;
> -	int i;
> +	int ret, i;
> +
> +	if (ep->core_init_notifier) {
> +		ret = dw_pcie_iatu_config(ep);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	if (ep->core_init_notifier) {
> +		ret = dw_pcie_ep_func_init(ep);
> +		if (ret)
> +			return ret;
> +
> +		if (ep->ops->ep_init)
> +			ep->ops->ep_init(ep);
> +	}
>  
>  	hdr_type = dw_pcie_readb_dbi(pci, PCI_HEADER_TYPE) &
>  		   PCI_HEADER_TYPE_MASK;
> @@ -677,8 +749,6 @@ 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 +756,12 @@ 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;
> +
> +	if (ep->ops->get_features) {
> +		epc_features = ep->ops->get_features(ep);
> +		if (epc_features->core_init_notifier)
> +			ep->core_init_notifier = true;
> +	}
>  
>  	INIT_LIST_HEAD(&ep->func_list);
>  
> @@ -708,7 +783,11 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>  		}
>  	}
>  
> -	dw_pcie_iatu_detect(pci);
> +	if (!ep->core_init_notifier) {
> +		ret = dw_pcie_iatu_config(ep);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "addr_space");
>  	if (!res)
> @@ -717,26 +796,6 @@ 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);
>  
> @@ -753,23 +812,15 @@ 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);
> +	if (!ep->core_init_notifier) {
> +		ret = dw_pcie_ep_func_init(ep);
> +		if (ret)
> +			return ret;
>  
> -		list_add_tail(&ep_func->list, &ep->func_list);
> +		if (ep->ops->ep_init)
> +			ep->ops->ep_init(ep);
>  	}
>  
> -	if (ep->ops->ep_init)
> -		ep->ops->ep_init(ep);
> -
>  	ret = pci_epc_mem_init(epc, ep->phys_base, ep->addr_size,
>  			       ep->page_size);
>  	if (ret < 0) {
> @@ -784,12 +835,9 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>  		return -ENOMEM;
>  	}
>  
> -	if (ep->ops->get_features) {
> -		epc_features = ep->ops->get_features(ep);
> -		if (epc_features->core_init_notifier)
> -			return 0;
> -	}
> +	if (!ep->core_init_notifier)
> +		return dw_pcie_ep_init_complete(ep);
>  
> -	return dw_pcie_ep_init_complete(ep);
> +	return 0;
>  }
>  EXPORT_SYMBOL_GPL(dw_pcie_ep_init);
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 7d6e9b7576be..aadb14159df7 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -242,6 +242,7 @@ struct dw_pcie_ep {
>  	void __iomem		*msi_mem;
>  	phys_addr_t		msi_mem_phys;
>  	struct pci_epf_bar	*epf_bar[PCI_STD_NUM_BARS];
> +	bool			core_init_notifier;
>  };
>  
>  struct dw_pcie_ops {
> -- 
> 2.25.1
>