[PATCH v9 08/10] PCI: dwc: ep: Add a generic dw_pcie_ep_linkdown() API to handle LINK_DOWN event

Manivannan Sadhasivam
2024-03-04T09:24:09Z

The PCIe link can go to LINK_DOWN state in one of the following scenarios:

1. Fundamental (PERST#)/hot/warm reset
2. Link transition from L2/L3 to L0

In those cases, LINK_DOWN causes some non-sticky DWC registers to loose the
state (like REBAR, PTM_CAP etc...). So the 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
let's 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.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
drivers/pci/controller/dwc/pcie-designware-ep.c | 111 ++++++++++++++----------
drivers/pci/controller/dwc/pcie-designware.h | 5 ++
2 files changed, 72 insertions(+), 44 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
index 278bdc9b2269..fed4c2936c78 100644
--- a/drivers/pci/controller/dwc/pcie-designware-ep.c
+++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
@@ -14,14 +14,6 @@
#include <linux/pci-epc.h>
#include <linux/pci-epf.h>

-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);
-
void dw_pcie_ep_init_notify(struct dw_pcie_ep *ep)
{
struct pci_epc *epc = ep->epc;
@@ -603,19 +595,56 @@ 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, ptm_cap_base;
+ unsigned int nbars;
+ u32 reg, i;
+
+ 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;
+
+ for (i = 0; i < nbars; i++, offset += PCI_REBAR_CTRL)
+ dw_pcie_writel_dbi(pci, offset + PCI_REBAR_CAP, 0x0);
+ }
+
+ /*
+ * PTM responder capability can be disabled only after disabling
+ * PTM root capability.
+ */
+ if (ptm_cap_base) {
+ dw_pcie_dbi_ro_wr_en(pci);
+ reg = dw_pcie_readl_dbi(pci, ptm_cap_base + PCI_PTM_CAP);
+ reg &= ~PCI_PTM_CAP_ROOT;
+ dw_pcie_writel_dbi(pci, ptm_cap_base + PCI_PTM_CAP, reg);
+
+ reg = dw_pcie_readl_dbi(pci, ptm_cap_base + PCI_PTM_CAP);
+ reg &= ~(PCI_PTM_CAP_RES | PCI_PTM_GRANULARITY_MASK);
+ dw_pcie_writel_dbi(pci, ptm_cap_base + PCI_PTM_CAP, reg);
+ dw_pcie_dbi_ro_wr_dis(pci);
+ }
+
+ dw_pcie_setup(pci);
+ dw_pcie_dbi_ro_wr_dis(pci);
+}
+
int dw_pcie_ep_init_registers(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, ptm_cap_base;
- unsigned int nbars;
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;
@@ -678,38 +707,7 @@ 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;
-
- for (i = 0; i < nbars; i++, offset += PCI_REBAR_CTRL)
- dw_pcie_writel_dbi(pci, offset + PCI_REBAR_CAP, 0x0);
- }
-
- /*
- * PTM responder capability can be disabled only after disabling
- * PTM root capability.
- */
- if (ptm_cap_base) {
- dw_pcie_dbi_ro_wr_en(pci);
- reg = dw_pcie_readl_dbi(pci, ptm_cap_base + PCI_PTM_CAP);
- reg &= ~PCI_PTM_CAP_ROOT;
- dw_pcie_writel_dbi(pci, ptm_cap_base + PCI_PTM_CAP, reg);
-
- reg = dw_pcie_readl_dbi(pci, ptm_cap_base + PCI_PTM_CAP);
- reg &= ~(PCI_PTM_CAP_RES | PCI_PTM_GRANULARITY_MASK);
- dw_pcie_writel_dbi(pci, ptm_cap_base + PCI_PTM_CAP, reg);
- 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;

@@ -720,6 +718,31 @@ int dw_pcie_ep_init_registers(struct dw_pcie_ep *ep)
}
EXPORT_SYMBOL_GPL(dw_pcie_ep_init_registers);

+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);
+
+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);
+
int dw_pcie_ep_init(struct dw_pcie_ep *ep)
{
int ret;
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index f8e5431a207b..152969545b0a 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -668,6 +668,7 @@ 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);
@@ -688,6 +689,10 @@ 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;

--
2.25.1