Re: [PATCH v3 2/2] PCI: cadence: Add debugfs property to provide LTSSM status of the PCIe link

From: Manivannan Sadhasivam

Date: Wed May 06 2026 - 11:45:13 EST

On Mon, Apr 06, 2026 at 06:32:37PM +0800, Hans Zhang wrote:
> Add the debugfs property to provide a view of the current link's LTSSM
> status from the Root Port device.
>
> Test example:
> # cat /sys/kernel/debug/cdns_pcie_a0c0000.pcie/ltssm_status
> L0_STATE (0x29)
>
> Signed-off-by: Hans Zhang <18255117159@xxxxxxx>
> ---
> Documentation/ABI/testing/debugfs-cdns-pcie | 5 +
> drivers/pci/controller/cadence/Kconfig | 9 +
> drivers/pci/controller/cadence/Makefile | 1 +
> drivers/pci/controller/cadence/pci-sky1.c | 3 +
> .../controller/cadence/pcie-cadence-debugfs.c | 215 ++++++++++++++++++
> .../pci/controller/cadence/pcie-cadence-ep.c | 3 +
> .../cadence/pcie-cadence-host-hpa.c | 8 +-
> .../controller/cadence/pcie-cadence-host.c | 9 +-
> drivers/pci/controller/cadence/pcie-cadence.h | 145 ++++++++++++
> 9 files changed, 396 insertions(+), 2 deletions(-)
> create mode 100644 Documentation/ABI/testing/debugfs-cdns-pcie
> create mode 100644 drivers/pci/controller/cadence/pcie-cadence-debugfs.c
>
> diff --git a/Documentation/ABI/testing/debugfs-cdns-pcie b/Documentation/ABI/testing/debugfs-cdns-pcie
> new file mode 100644
> index 000000000000..659ad2ab70e4
> --- /dev/null
> +++ b/Documentation/ABI/testing/debugfs-cdns-pcie
> @@ -0,0 +1,5 @@
> +What: /sys/kernel/debug/cdns_pcie_<dev>/ltssm_status
> +Date: March 2026
> +Contact: Hans Zhang <18255117159@xxxxxxx>
> +Description: (RO) Read will return the current PCIe LTSSM state in both
> + string and raw value.
> diff --git a/drivers/pci/controller/cadence/Kconfig b/drivers/pci/controller/cadence/Kconfig
> index 9e651d545973..b277c5f6e196 100644
> --- a/drivers/pci/controller/cadence/Kconfig
> +++ b/drivers/pci/controller/cadence/Kconfig
> @@ -6,6 +6,15 @@ menu "Cadence-based PCIe controllers"
> config PCIE_CADENCE
> tristate
>
> +config PCIE_CADENCE_DEBUGFS
> + bool "Cadence PCIe debugfs entries"

Why not tristate?

> + depends on DEBUG_FS
> + depends on PCIE_CADENCE_HOST || PCIE_CADENCE_EP
> + help
> + Say Y here to enable debugfs entries for the PCIe controller. These
> + entries provide various debug features related to the controller and
> + the LTSSM status of link can be displayed.
> +
> config PCIE_CADENCE_HOST
> tristate
> depends on OF
> diff --git a/drivers/pci/controller/cadence/Makefile b/drivers/pci/controller/cadence/Makefile
> index b8ec1cecfaa8..2cdc4617e0c2 100644
> --- a/drivers/pci/controller/cadence/Makefile
> +++ b/drivers/pci/controller/cadence/Makefile
> @@ -4,6 +4,7 @@ pcie-cadence-host-mod-y := pcie-cadence-host-common.o pcie-cadence-host.o pcie-c
> pcie-cadence-ep-mod-y := pcie-cadence-ep.o
>
> obj-$(CONFIG_PCIE_CADENCE) = pcie-cadence-mod.o
> +obj-$(CONFIG_PCIE_CADENCE_DEBUGFS) += pcie-cadence-debugfs.o
> obj-$(CONFIG_PCIE_CADENCE_HOST) += pcie-cadence-host-mod.o
> obj-$(CONFIG_PCIE_CADENCE_EP) += pcie-cadence-ep-mod.o
> obj-$(CONFIG_PCIE_CADENCE_PLAT) += pcie-cadence-plat.o
> diff --git a/drivers/pci/controller/cadence/pci-sky1.c b/drivers/pci/controller/cadence/pci-sky1.c
> index e1f4a98e2ab6..093f20466339 100644
> --- a/drivers/pci/controller/cadence/pci-sky1.c
> +++ b/drivers/pci/controller/cadence/pci-sky1.c
> @@ -221,7 +221,10 @@ MODULE_DEVICE_TABLE(of, of_sky1_pcie_match);
> static void sky1_pcie_remove(struct platform_device *pdev)
> {
> struct sky1_pcie *pcie = platform_get_drvdata(pdev);
> + struct cdns_pcie_rc *rc;
>
> + rc = container_of(pcie->cdns_pcie, struct cdns_pcie_rc, pcie);
> + cdns_pcie_debugfs_deinit(&rc->pcie);

You are calling cdns_pcie_debugfs_init() from pcie-cadence-host-hpa.c driver. So
you should call cdns_pcie_debugfs_deinit() there only in an exported API.

> pci_ecam_free(pcie->cfg);
> }
>
> diff --git a/drivers/pci/controller/cadence/pcie-cadence-debugfs.c b/drivers/pci/controller/cadence/pcie-cadence-debugfs.c
> new file mode 100644
> index 000000000000..d83007ae218e
> --- /dev/null
> +++ b/drivers/pci/controller/cadence/pcie-cadence-debugfs.c
> @@ -0,0 +1,215 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Cadence PCIe controller debugfs driver
> + *
> + * Copyright (C) 2026 Hans Zhang <18255117159@xxxxxxx>
> + * Author: Hans Zhang <18255117159@xxxxxxx>

Since copyright belongs to you, there is no need to mention 'Author'.

> + */
> +
> +#include <linux/debugfs.h>
> +
> +#include "pcie-cadence.h"
> +
> +#define CDNS_DEBUGFS_BUF_MAX 128
> +#define CDNS_PCIE_LGA_LTSSM_STATUS_MASK GENMASK(29, 24)
> +#define CDNS_PCIE_HPA_LTSSM_STATUS_MASK GENMASK(27, 20)
> +
> +static const char *cdns_pcie_ltssm_status_string(enum cdns_pcie_ltssm ltssm)
> +{
> + const char *str;
> +
> + switch (ltssm) {
> +#define CDNS_PCIE_LTSSM_NAME(n) case n: str = #n; break
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DETECT_QUIET);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DETECT_QUIET_ENTRY);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DETECT_ACTIVE);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DETECT_ACTIVE_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DETECT_ACTIVE_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DETECT_ACTIVE_3);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RCVR_DETECTED_ST);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RCVR_DETECTED_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_ACTIVE);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_ACTIVE_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_ACTIVE_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_ACTIVE_3);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_COMPLIANCE);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_COMPLIANCE_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_CONFIG);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_CONFIG_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_CONFIG_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LW_START_RC);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LW_START_RC_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LW_START_RC_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LW_ACC_RC);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LANENUM_WAIT_RC);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LANENUM_WAIT_RC_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LANENUM_ACC_RC);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LW_START_EP);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LW_START_EP_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LW_START_EP_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LW_ACC_EP);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LANENUM_WAIT_EP);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LANENUM_WAIT_EP_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LANENUM_ACC_EP);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_LANENUM_ACC_EP_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DUMMY_STATE_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_COMPLETE);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_COMPLETE_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_COMPLETE_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_IDLE);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_CONFIG_IDLE_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DUMMY_STATE_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DUMMY_STATE_3);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DUMMY_STATE_4);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L0_STATE);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_RCVR_LOCK);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_RCVR_LOCK_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_RCVR_CFG);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_RCVR_CFG_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_IDLE);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_IDLE_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DISABLE_LINK);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DISABLE_LINK_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DISABLE_LINK_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DISABLE_LINK_3);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DISABLE_LINK_4);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DISABLE_LINK_5);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DISABLE_LINK_6);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_DISABLE_LINK_7);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_HOT_RESET);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_HOT_RESET_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_HOT_RESET_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_HOT_RESET_3);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L0S_ENTRY);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L0S_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L0S_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L0S_3);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L0S_4);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L0S_5);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_WAIT_FOR_LINK_TX);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_TX_FTS_ENTRY);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_TX_FTS_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_TX_FTS_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_TX_ELEC_IDLE_ST);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_TX_ELEC_IDLE_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_TX_ELEC_IDLE_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_TX_ELEC_IDLE_3);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_SPEED);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_SPEED_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_SPEED_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_SPEED_3);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_COMPLIANCE_GEN23);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_COMPLIANCE_GEN23_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_COMPLIANCE_GEN23_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_COMPLIANCE_GEN23_3);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_COMPLIANCE_GEN23_4);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_COMPLIANCE_GEN23_5);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_COMPLIANCE_GEN23_6);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_COMPLIANCE_GEN23_7);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_POLLING_COMPLIANCE_GEN23_8);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_SLAVE_ENTRY);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_SLAVE_ENTRY_FROM_RECOVERY);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_SLAVE_EXIT_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_SLAVE_EXIT);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_SLAVE_GEN2_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_SLAVE_GEN2_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_SLAVE_GEN2_3);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_SLAVE_GEN2_4);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_SLAVE_GEN2_5);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_SLAVE_ACTIVE);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L1_ENTRY);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L1_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L1_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L1_3);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L1_4);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L1_IDLE);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L1_EXIT);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L2_ENTRY);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L2_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L2_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L2_3);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L2_4);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L2_5);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_L2_IDLE);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_MASTER_ENTRY);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_MASTER_ENTRY_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_MASTER_ENTRY_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_MASTER_ENTRY_3);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_MASTER_ENTRY_4);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_MASTER_ENTRY_5);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_MASTER_ENTRY_FROM_RECOVERY);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_MASTER_ACTIVE);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_MASTER_EXIT);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_MASTER_EXIT_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_LOOPBACK_MASTER_EXIT_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_EQUALIZATION_PHASE0);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_EQUALIZATION_PHASE1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_EQUALIZATION_PHASE2_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_EQUALIZATION_PHASE2_2);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_EQUALIZATION_PHASE3_1);
> + CDNS_PCIE_LTSSM_NAME(CDNS_PCIE_LTSSM_RECOVERY_EQUALIZATION_PHASE3_2);
> + default:
> + str = "CDNS_PCIE_LTSSM_UNKNOWN";
> + break;
> + }
> +
> + return str + strlen("CDNS_PCIE_LTSSM_");
> +}
> +
> +static int ltssm_status_show(struct seq_file *s, void *v)
> +{
> + struct cdns_pcie *pci = s->private;
> + enum cdns_pcie_ltssm ltssm;
> + u32 reg;
> +
> + if (pci->is_hpa) {
> + reg = cdns_pcie_hpa_readl(pci, REG_BANK_IP_REG,
> + CDNS_PCIE_HPA_PHY_DBG_STS_REG0);
> + ltssm = FIELD_GET(CDNS_PCIE_HPA_LTSSM_STATUS_MASK, reg);
> + } else {
> + reg = cdns_pcie_readl(pci, CDNS_PCIE_LM_BASE);
> + ltssm = FIELD_GET(CDNS_PCIE_LGA_LTSSM_STATUS_MASK, reg);
> + }
> +
> + seq_printf(s, "%s (0x%02x)\n", cdns_pcie_ltssm_status_string(ltssm), ltssm);
> +
> + return 0;
> +}
> +
> +static int ltssm_status_open(struct inode *inode, struct file *file)
> +{
> + return single_open(file, ltssm_status_show, inode->i_private);
> +}
> +
> +static const struct file_operations cdns_pcie_ltssm_status_ops = {
> + .open = ltssm_status_open,
> + .read = seq_read,
> +};

Sashiko pointed out that you could use DEFINE_SHOW_ATTRIBUTE() to simplify the
code here.

- Mani

--
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