Re: [PATCH v2 2/5] PCI: iproc: Fix up corrupted PAXC root complex config registers

From: poza
Date: Tue Jun 12 2018 - 08:23:23 EST

On 2018-06-12 13:57, poza@xxxxxxxxxxxxxx wrote:
On 2018-06-12 05:51, Ray Jui wrote:
On certain versions of Broadcom PAXC based root complexes, certain
regions of the configuration space are corrupted. As a result, it
prevents the Linux PCIe stack from traversing the linked list of the
capability registers completely and therefore the root complex is
not advertised as "PCIe capable". This prevents the correct PCIe RID
from being parsed in the kernel PCIe stack. A correct RID is required
for mapping to a stream ID from the SMMU or the device ID from the
GICv3 ITS

This patch fixes up the issue by manually populating the related
PCIe capabilities

Signed-off-by: Ray Jui <rjui@xxxxxxxxxxxx>
---
drivers/pci/host/pcie-iproc.c | 65 +++++++++++++++++++++++++++++++++++++++----
drivers/pci/host/pcie-iproc.h | 3 ++
2 files changed, 62 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/host/pcie-iproc.c b/drivers/pci/host/pcie-iproc.c
index 3c76c5f..680f6b1 100644
--- a/drivers/pci/host/pcie-iproc.c
+++ b/drivers/pci/host/pcie-iproc.c
@@ -85,6 +85,8 @@
#define IMAP_VALID_SHIFT 0
#define IMAP_VALID BIT(IMAP_VALID_SHIFT)

+#define IPROC_PCI_PM_CAP 0x48
+#define IPROC_PCI_PM_CAP_MASK 0xffff
#define IPROC_PCI_EXP_CAP 0xac

#define IPROC_PCIE_REG_INVALID 0xffff
@@ -375,6 +377,17 @@ static const u16 iproc_pcie_reg_paxc_v2[] = {
[IPROC_PCIE_CFG_DATA] = 0x1fc,
};

+/*
+ * List of device IDs of controllers that have corrupted capability list that
+ * require SW fixup
+ */
+static const u16 iproc_pcie_corrupt_cap_did[] = {
+ 0x16cd,
+ 0x16f0,
+ 0xd802,
+ 0xd804
+};
+
static inline struct iproc_pcie *iproc_data(struct pci_bus *bus)
{
struct iproc_pcie *pcie = bus->sysdata;
@@ -495,6 +508,49 @@ static unsigned int iproc_pcie_cfg_retry(void
__iomem *cfg_data_p)
return data;
}

+static void iproc_pcie_fix_cap(struct iproc_pcie *pcie, int where, u32 *val)
+{
+ u32 i, dev_id;
+
+ switch (where & ~0x3) {
+ case PCI_VENDOR_ID:
+ dev_id = *val >> 16;
+
+ /*
+ * Activate fixup for those controllers that have corrupted
+ * capability list registers
+ */
+ for (i = 0; i < ARRAY_SIZE(iproc_pcie_corrupt_cap_did); i++)
+ if (dev_id == iproc_pcie_corrupt_cap_did[i])
+ pcie->fix_paxc_cap = true;

and I think this code will try to fix up every time config space is read.
Does this get corrupted often, randomly ?
Can it not be solved by using one time Quirk ?
and if not Quirk, you dont want to be setting pcie->fix_paxc_cap =
false somewhere

besides, pcie->fix_paxc_cap = true; is set if PCI_VENDOR_ID is read first.
and rest cases stay with the assumption that PCI_VENDOR_ID will be read first.
which is infact read first during enumeration
(that is the assumption code is making), but that is safe assumption
to make I think.


ok I see that Bjorn has suggested to fix it this way instead of Quirks.
will just mark

Reviewed-by: Oza Pawandeep <poza@xxxxxxxxxxxxxx>

+ break;
+
+ case IPROC_PCI_PM_CAP:
+ if (pcie->fix_paxc_cap) {
+ /* advertise PM, force next capability to PCIe */
+ *val &= ~IPROC_PCI_PM_CAP_MASK;
+ *val |= IPROC_PCI_EXP_CAP << 8 | PCI_CAP_ID_PM;
+ }
+ break;
+
+ case IPROC_PCI_EXP_CAP:
+ if (pcie->fix_paxc_cap) {
+ /* advertise root port, version 2, terminate here */
+ *val = (PCI_EXP_TYPE_ROOT_PORT << 4 | 2) << 16 |
+ PCI_CAP_ID_EXP;
+ }
+ break;
+
+ case IPROC_PCI_EXP_CAP + PCI_EXP_RTCTL:
+ /* Don't advertise CRS SV support */
+ *val &= ~(PCI_EXP_RTCAP_CRSVIS << 16);
+ break;
+
+ default:
+ break;
+ }
+}
+
static int iproc_pcie_config_read(struct pci_bus *bus, unsigned int devfn,
int where, int size, u32 *val)
{
@@ -509,13 +565,10 @@ static int iproc_pcie_config_read(struct pci_bus
*bus, unsigned int devfn,
/* root complex access */
if (busno == 0) {
ret = pci_generic_config_read32(bus, devfn, where, size, val);
- if (ret != PCIBIOS_SUCCESSFUL)
- return ret;
+ if (ret == PCIBIOS_SUCCESSFUL)
+ iproc_pcie_fix_cap(pcie, where, val);

- /* Don't advertise CRS SV support */
- if ((where & ~0x3) == IPROC_PCI_EXP_CAP + PCI_EXP_RTCTL)
- *val &= ~(PCI_EXP_RTCAP_CRSVIS << 16);
- return PCIBIOS_SUCCESSFUL;
+ return ret;
}

cfg_data_p = iproc_pcie_map_ep_cfg_reg(pcie, busno, slot, fn, where);
diff --git a/drivers/pci/host/pcie-iproc.h b/drivers/pci/host/pcie-iproc.h
index 814b600..9d5cfee 100644
--- a/drivers/pci/host/pcie-iproc.h
+++ b/drivers/pci/host/pcie-iproc.h
@@ -60,6 +60,8 @@ struct iproc_msi;
* @ep_is_internal: indicates an internal emulated endpoint device is connected
* @has_apb_err_disable: indicates the controller can be configured to prevent
* unsupported request from being forwarded as an APB bus error
+ * @fix_paxc_cap: indicates the controller has corrupted capability list in its
+ * config space registers and requires SW based fixup
*
* @need_ob_cfg: indicates SW needs to configure the outbound mapping window
* @ob: outbound mapping related parameters
@@ -85,6 +87,7 @@ struct iproc_pcie {
int (*map_irq)(const struct pci_dev *, u8, u8);
bool ep_is_internal;
bool has_apb_err_disable;
+ bool fix_paxc_cap;

bool need_ob_cfg;
struct iproc_pcie_ob ob;