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PCI: dwc: ep: Add a generic dw_pcie_ep_linkdown() API to handle Link Down event

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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: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
[bhelgaas: update spec citation]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Niklas Cassel <cassel@kernel.org>
This commit is contained in:
Manivannan Sadhasivam 2024-04-30 11:43:49 +05:30 committed by Bjorn Helgaas
parent e1a4ec1a95
commit 867ab111b2
2 changed files with 73 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

103
drivers/pci/controller/dwc/pcie-designware-ep.c
View File

@ -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 @@ err_remove_edma:
}
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

5
drivers/pci/controller/dwc/pcie-designware.h
View File

@ -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;