Re: [PATCH v2 02/15] PCI: rcar-gen4: Check live link status in link_up()
From: Marek Vasut
Date: Sat Oct 03 2026 - 16:04:47 EST
On 10/3/26 8:29 PM, Marek Vasut wrote:
On 9/28/26 6:52 PM, Koichiro Den wrote:
rcar_gen4_pcie_link_up() checks link state using SMLH_LINK_UP and
RDLH_LINK_UP in PCIEINTSTS0. However, these bits do not reflect the live
link state. On an R-Car S4, after taking down the endpoint, a link-down
interrupt saw PCIEINTSTS0 = 0x20a000c5 with both bits still set. Even
after resetting the controller with the LTSSM back in Polling, they read
0xa000c5, still set.
As a result, dw_pcie_link_up() keeps reporting the link as up after it
has gone down. That defeats the check in dw_pcie_other_conf_map_bus(),
which is supposed to stop config accesses to downstream devices while
the link is down, so such accesses go out on the dead link and stall the
host. It also makes the callback useless for the link-down recovery
added later, which has to wait for the link to actually come back after
resetting the controller.
Keep the APP link-up event check from Figure 104.5 of the R-Car S4
reference manual, but also require PORT_DEBUG1 to report the link up and
not in training. The callback then rejects a downed link even if the APP
link-up events remain latched.
Clear the APP latches before enabling LTSSM to discard events from a
previous start, and only read them in .link_up(). RC startup uses
dw_pcie_wait_for_link() to poll the combined condition.
Fixes: 0d0c551011df ("PCI: rcar-gen4: Add R-Car Gen4 PCIe controller support for host mode")
Suggested-by: Marek Vasut <marek.vasut+renesas@xxxxxxxxxxx>
Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
I apologize for the late reply.
Reviewed-by: Marek Vasut <marek.vasut+renesas@xxxxxxxxxxx>
Tested-by: Marek Vasut <marek.vasut+renesas@xxxxxxxxxxx> # R-Car V4H
Since next 20261002 now contains commit
f29719b5064c ("PCI: dwc: Align register macros with Synopsys documentation")
This will need the following slight adjustment:
"s@PCIE_PORT_DEBUG@PORT_LINK_DEBUG@g"
"
- val = dw_pcie_readl_dbi(dw, PCIE_PORT_DEBUG1);
- return (val & PCIE_PORT_DEBUG1_LINK_UP) &&
- !(val & PCIE_PORT_DEBUG1_LINK_IN_TRAINING);
+ val = dw_pcie_readl_dbi(dw, PORT_LINK_DEBUG1);
+ return (val & PORT_LINK_DEBUG1_LINK_UP) &&
+ !(val & PORT_LINK_DEBUG1_LINK_IN_TRAINING);
"
A small nitpick, would the following change make sense to reduce duplication a bit ?
diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index c726aa71c830c..52bdb1fcc2db2 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -817,17 +817,23 @@ int dw_pcie_wait_for_link(struct dw_pcie *pci)
}
EXPORT_SYMBOL_GPL(dw_pcie_wait_for_link);
-bool dw_pcie_link_up(struct dw_pcie *pci)
+bool dw_pcie_link_up_debug_check(struct dw_pcie *pci)
{
u32 val;
- if (pci->ops && pci->ops->link_up)
- return pci->ops->link_up(pci);
-
val = dw_pcie_readl_dbi(pci, PORT_LINK_DEBUG1);
return ((val & PORT_LINK_DEBUG1_LINK_UP) &&
(!(val & PORT_LINK_DEBUG1_LINK_IN_TRAINING)));
}
+EXPORT_SYMBOL_GPL(dw_pcie_link_up_debug_check);
+
+bool dw_pcie_link_up(struct dw_pcie *pci)
+{
+ if (pci->ops && pci->ops->link_up)
+ return pci->ops->link_up(pci);
+
+ return dw_pcie_link_up_debug_check(pci);
+}
EXPORT_SYMBOL_GPL(dw_pcie_link_up);
void dw_pcie_upconfig_setup(struct dw_pcie *pci)
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 4199324882800..2ce61709b58c2 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -618,6 +618,7 @@ int dw_pcie_write(void __iomem *addr, int size, u32 val);
u32 dw_pcie_read_dbi(struct dw_pcie *pci, u32 reg, size_t size);
void dw_pcie_write_dbi(struct dw_pcie *pci, u32 reg, size_t size, u32 val);
void dw_pcie_write_dbi2(struct dw_pcie *pci, u32 reg, size_t size, u32 val);
+bool dw_pcie_link_up_debug_check(struct dw_pcie *pci);
bool dw_pcie_link_up(struct dw_pcie *pci);
void dw_pcie_upconfig_setup(struct dw_pcie *pci);
int dw_pcie_wait_for_link(struct dw_pcie *pci);
diff --git a/drivers/pci/controller/dwc/pcie-rcar-gen4.c b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
index dbc0115885afc..b2ed1a329c418 100644
--- a/drivers/pci/controller/dwc/pcie-rcar-gen4.c
+++ b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
@@ -127,9 +127,7 @@ static bool rcar_gen4_pcie_link_up(struct dw_pcie *dw)
return false;
/* The APP link-up events remain latched after the link goes down. */
- val = dw_pcie_readl_dbi(dw, PORT_LINK_DEBUG1);
- return (val & PORT_LINK_DEBUG1_LINK_UP) &&
- !(val & PORT_LINK_DEBUG1_LINK_IN_TRAINING);
+ return dw_pcie_link_up_debug_check(dw);
}
/*