Commit 867ab111 authored by Manivannan Sadhasivam's avatar Manivannan Sadhasivam Committed by Bjorn Helgaas
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PCI: dwc: ep: Add a generic dw_pcie_ep_linkdown() API to handle Link Down event 

Per PCIe r6.0, sec 5.2, a Link Down event can happen under any of the
following circumstances:

  1. Fundamental/Hot reset
  2. Link disable transmission by upstream component
  3. Moving from L2/L3 to L0

In those cases, Link Down causes some non-sticky DWC registers to lose the
state (like REBAR, etc.), so drivers need to reinitialize them to function
properly once the link comes back again.

This is not a problem for drivers supporting PERST# IRQ, since they can
reinitialize the registers in the PERST# IRQ callback. But for the drivers
not supporting PERST#, there is no way they can reinitialize the registers
other than relying on Link Down IRQ received when the link goes down. So
add a DWC generic API dw_pcie_ep_linkdown() that reinitializes the
non-sticky registers and also notifies the EPF drivers about link going
down.

This API can also be used by the drivers supporting PERST# to handle the
scenario (2) mentioned above.

NOTE: For the sake of code organization, move the dw_pcie_ep_linkup()
definition just above dw_pcie_ep_linkdown().

Link: https://lore.kernel.org/linux-pci/20240430-pci-epf-rework-v4-8-22832d0d456f@linaro.org


Tested-by: default avatarNiklas Cassel <cassel@kernel.org>
Signed-off-by: default avatarManivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: default avatarKrzysztof Wilczyński <kwilczynski@kernel.org>
[bhelgaas: update spec citation]
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: default avatarNiklas Cassel <cassel@kernel.org>
parent e1a4ec1a

drivers/pci/controller/dwc/pcie-designware-ep.c

+68 −35
Original line number Diff line number Diff line
@@ -15,18 +15,6 @@ 
#include <linux/pci-epc.h>

#include <linux/pci-epf.h>



/**

 * dw_pcie_ep_linkup - Notify EPF drivers about Link Up event

 * @ep: DWC EP device

 */

void dw_pcie_ep_linkup(struct dw_pcie_ep *ep)

{

	struct pci_epc *epc = ep->epc;



	pci_epc_linkup(epc);

}

EXPORT_SYMBOL_GPL(dw_pcie_ep_linkup);



/**

 * dw_pcie_ep_init_notify - Notify EPF drivers about EPC initialization complete

 * @ep: DWC EP device
@@ -685,6 +673,34 @@ static unsigned int dw_pcie_ep_find_ext_capability(struct dw_pcie *pci, int cap) 
	return 0;

}



static void dw_pcie_ep_init_non_sticky_registers(struct dw_pcie *pci)

{

	unsigned int offset;

	unsigned int nbars;

	u32 reg, i;



	offset = dw_pcie_ep_find_ext_capability(pci, PCI_EXT_CAP_ID_REBAR);



	dw_pcie_dbi_ro_wr_en(pci);



	if (offset) {

		reg = dw_pcie_readl_dbi(pci, offset + PCI_REBAR_CTRL);

		nbars = (reg & PCI_REBAR_CTRL_NBAR_MASK) >>

			PCI_REBAR_CTRL_NBAR_SHIFT;



		/*

		 * PCIe r6.0, sec 7.8.6.2 require us to support at least one

		 * size in the range from 1 MB to 512 GB. Advertise support

		 * for 1 MB BAR size only.

		 */

		for (i = 0; i < nbars; i++, offset += PCI_REBAR_CTRL)

			dw_pcie_writel_dbi(pci, offset + PCI_REBAR_CAP, 0x0);

	}



	dw_pcie_setup(pci);

	dw_pcie_dbi_ro_wr_dis(pci);

}



/**

 * dw_pcie_ep_init_registers - Initialize DWC EP specific registers

 * @ep: DWC EP device
@@ -699,13 +715,11 @@ int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep) 
	struct dw_pcie_ep_func *ep_func;

	struct device *dev = pci->dev;

	struct pci_epc *epc = ep->epc;

	unsigned int offset, ptm_cap_base;

	unsigned int nbars;

	u32 ptm_cap_base, reg;

	u8 hdr_type;

	u8 func_no;

	int i, ret;

	void *addr;

	u32 reg;

	int ret;



	hdr_type = dw_pcie_readb_dbi(pci, PCI_HEADER_TYPE) &

		   PCI_HEADER_TYPE_MASK;
@@ -768,25 +782,8 @@ int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep) 
	if (ep->ops->init)

		ep->ops->init(ep);



	offset = dw_pcie_ep_find_ext_capability(pci, PCI_EXT_CAP_ID_REBAR);

	ptm_cap_base = dw_pcie_ep_find_ext_capability(pci, PCI_EXT_CAP_ID_PTM);



	dw_pcie_dbi_ro_wr_en(pci);



	if (offset) {

		reg = dw_pcie_readl_dbi(pci, offset + PCI_REBAR_CTRL);

		nbars = (reg & PCI_REBAR_CTRL_NBAR_MASK) >>

			PCI_REBAR_CTRL_NBAR_SHIFT;



		/*

		 * PCIe r6.0, sec 7.8.6.2 require us to support at least one

		 * size in the range from 1 MB to 512 GB. Advertise support

		 * for 1 MB BAR size only.

		 */

		for (i = 0; i < nbars; i++, offset += PCI_REBAR_CTRL)

			dw_pcie_writel_dbi(pci, offset + PCI_REBAR_CAP, BIT(4));

	}



	/*

	 * PTM responder capability can be disabled only after disabling

	 * PTM root capability.
@@ -803,8 +800,7 @@ int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep) 
		dw_pcie_dbi_ro_wr_dis(pci);

	}



	dw_pcie_setup(pci);

	dw_pcie_dbi_ro_wr_dis(pci);

	dw_pcie_ep_init_non_sticky_registers(pci);



	return 0;
@@ -815,6 +811,43 @@ int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep) 
}

EXPORT_SYMBOL_GPL(dw_pcie_ep_init_registers);



/**

 * dw_pcie_ep_linkup - Notify EPF drivers about Link Up event

 * @ep: DWC EP device

 */

void dw_pcie_ep_linkup(struct dw_pcie_ep *ep)

{

	struct pci_epc *epc = ep->epc;



	pci_epc_linkup(epc);

}

EXPORT_SYMBOL_GPL(dw_pcie_ep_linkup);



/**

 * dw_pcie_ep_linkdown - Notify EPF drivers about Link Down event

 * @ep: DWC EP device

 *

 * Non-sticky registers are also initialized before sending the notification to

 * the EPF drivers. This is needed since the registers need to be initialized

 * before the link comes back again.

 */

void dw_pcie_ep_linkdown(struct dw_pcie_ep *ep)

{

	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);

	struct pci_epc *epc = ep->epc;



	/*

	 * Initialize the non-sticky DWC registers as they would've reset post

	 * Link Down. This is specifically needed for drivers not supporting

	 * PERST# as they have no way to reinitialize the registers before the

	 * link comes back again.

	 */

	dw_pcie_ep_init_non_sticky_registers(pci);



	pci_epc_linkdown(epc);

}

EXPORT_SYMBOL_GPL(dw_pcie_ep_linkdown);



/**

 * dw_pcie_ep_init - Initialize the endpoint device

 * @ep: DWC EP device

drivers/pci/controller/dwc/pcie-designware.h

+5 −0
Original line number Diff line number Diff line
@@ -681,6 +681,7 @@ static inline void __iomem *dw_pcie_own_conf_map_bus(struct pci_bus *bus, 


#ifdef CONFIG_PCIE_DW_EP

void dw_pcie_ep_linkup(struct dw_pcie_ep *ep);

void dw_pcie_ep_linkdown(struct dw_pcie_ep *ep);

int dw_pcie_ep_init(struct dw_pcie_ep *ep);

int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep);

void dw_pcie_ep_init_notify(struct dw_pcie_ep *ep);
@@ -701,6 +702,10 @@ static inline void dw_pcie_ep_linkup(struct dw_pcie_ep *ep) 
{

}



static inline void dw_pcie_ep_linkdown(struct dw_pcie_ep *ep)

{

}



static inline int dw_pcie_ep_init(struct dw_pcie_ep *ep)

{

	return 0;