2019-07-05 09:59:51

by Mika Westerberg

[permalink] [raw]
Subject: [PATCH 7/8] thunderbolt: Add support for Intel Ice Lake

The Thunderbolt controller is integrated into the Ice Lake CPU itself
and requires special flows to power it on and off using force power bit
in NHI VSEC registers. Runtime PM (RTD3) and Sx flows also differ from
the discrete solutions. Now the firmware notifies the driver whether
RTD3 entry or exit are possible. The driver is responsible of sending
Go2Sx command through link controller mailbox when system enters Sx
states (suspend-to-mem/disk). Rest of the ICM firwmare flows follow
Titan Ridge.

Signed-off-by: Raanan Avargil <[email protected]>
Signed-off-by: Mika Westerberg <[email protected]>
---
drivers/thunderbolt/icm.c | 151 ++++++++++++++++--
drivers/thunderbolt/nhi.c | 274 ++++++++++++++++++++++++++++++++-
drivers/thunderbolt/nhi.h | 2 +
drivers/thunderbolt/nhi_regs.h | 25 +++
drivers/thunderbolt/switch.c | 2 +
drivers/thunderbolt/tb_msgs.h | 16 +-
include/linux/thunderbolt.h | 2 +
7 files changed, 453 insertions(+), 19 deletions(-)

diff --git a/drivers/thunderbolt/icm.c b/drivers/thunderbolt/icm.c
index 2a56d9478b34..e882e79b32a4 100644
--- a/drivers/thunderbolt/icm.c
+++ b/drivers/thunderbolt/icm.c
@@ -56,16 +56,19 @@
* @max_boot_acl: Maximum number of preboot ACL entries (%0 if not supported)
* @rpm: Does the controller support runtime PM (RTD3)
* @can_upgrade_nvm: Can the NVM firmware be upgrade on this controller
+ * @veto: Is RTD3 veto in effect
* @is_supported: Checks if we can support ICM on this controller
* @cio_reset: Trigger CIO reset
* @get_mode: Read and return the ICM firmware mode (optional)
* @get_route: Find a route string for given switch
* @save_devices: Ask ICM to save devices to ACL when suspending (optional)
* @driver_ready: Send driver ready message to ICM
+ * @set_uuid: Set UUID for the root switch (optional)
* @device_connected: Handle device connected ICM message
* @device_disconnected: Handle device disconnected ICM message
* @xdomain_connected - Handle XDomain connected ICM message
* @xdomain_disconnected - Handle XDomain disconnected ICM message
+ * @rtd3_veto: Handle RTD3 veto notification ICM message
*/
struct icm {
struct mutex request_lock;
@@ -76,6 +79,7 @@ struct icm {
bool safe_mode;
bool rpm;
bool can_upgrade_nvm;
+ bool veto;
bool (*is_supported)(struct tb *tb);
int (*cio_reset)(struct tb *tb);
int (*get_mode)(struct tb *tb);
@@ -84,6 +88,7 @@ struct icm {
int (*driver_ready)(struct tb *tb,
enum tb_security_level *security_level,
size_t *nboot_acl, bool *rpm);
+ void (*set_uuid)(struct tb *tb);
void (*device_connected)(struct tb *tb,
const struct icm_pkg_header *hdr);
void (*device_disconnected)(struct tb *tb,
@@ -92,6 +97,7 @@ struct icm {
const struct icm_pkg_header *hdr);
void (*xdomain_disconnected)(struct tb *tb,
const struct icm_pkg_header *hdr);
+ void (*rtd3_veto)(struct tb *tb, const struct icm_pkg_header *hdr);
};

struct icm_notification {
@@ -519,14 +525,16 @@ static int icm_fr_disconnect_xdomain_paths(struct tb *tb, struct tb_xdomain *xd)
return 0;
}

-static void add_switch(struct tb_switch *parent_sw, u64 route,
- const uuid_t *uuid, const u8 *ep_name,
- size_t ep_name_size, u8 connection_id, u8 connection_key,
- u8 link, u8 depth, enum tb_security_level security_level,
- bool authorized, bool boot)
+static struct tb_switch *add_switch(struct tb_switch *parent_sw, u64 route,
+ const uuid_t *uuid, const u8 *ep_name,
+ size_t ep_name_size, u8 connection_id,
+ u8 connection_key, u8 link, u8 depth,
+ enum tb_security_level security_level,
+ bool authorized, bool boot)
{
const struct intel_vss *vss;
struct tb_switch *sw;
+ int ret;

pm_runtime_get_sync(&parent_sw->dev);

@@ -557,14 +565,18 @@ static void add_switch(struct tb_switch *parent_sw, u64 route,
tb_port_at(route, parent_sw)->remote = tb_upstream_port(sw);
tb_upstream_port(sw)->remote = tb_port_at(route, parent_sw);

- if (tb_switch_add(sw)) {
+ ret = tb_switch_add(sw);
+ if (ret) {
tb_port_at(tb_route(sw), parent_sw)->remote = NULL;
tb_switch_put(sw);
+ sw = ERR_PTR(ret);
}

out:
pm_runtime_mark_last_busy(&parent_sw->dev);
pm_runtime_put_autosuspend(&parent_sw->dev);
+
+ return sw;
}

static void update_switch(struct tb_switch *parent_sw, struct tb_switch *sw,
@@ -1086,7 +1098,8 @@ static int icm_tr_disconnect_xdomain_paths(struct tb *tb, struct tb_xdomain *xd)
}

static void
-icm_tr_device_connected(struct tb *tb, const struct icm_pkg_header *hdr)
+__icm_tr_device_connected(struct tb *tb, const struct icm_pkg_header *hdr,
+ bool force_rtd3)
{
const struct icm_tr_event_device_connected *pkg =
(const struct icm_tr_event_device_connected *)hdr;
@@ -1151,13 +1164,21 @@ icm_tr_device_connected(struct tb *tb, const struct icm_pkg_header *hdr)
return;
}

- add_switch(parent_sw, route, &pkg->ep_uuid, (const u8 *)pkg->ep_name,
- sizeof(pkg->ep_name), pkg->connection_id,
- 0, 0, 0, security_level, authorized, boot);
+ sw = add_switch(parent_sw, route, &pkg->ep_uuid, (const u8 *)pkg->ep_name,
+ sizeof(pkg->ep_name), pkg->connection_id, 0, 0, 0,
+ security_level, authorized, boot);
+ if (!IS_ERR(sw) && force_rtd3)
+ sw->rpm = true;

tb_switch_put(parent_sw);
}

+static void
+icm_tr_device_connected(struct tb *tb, const struct icm_pkg_header *hdr)
+{
+ __icm_tr_device_connected(tb, hdr, false);
+}
+
static void
icm_tr_device_disconnected(struct tb *tb, const struct icm_pkg_header *hdr)
{
@@ -1468,6 +1489,72 @@ static int icm_ar_set_boot_acl(struct tb *tb, const uuid_t *uuids,
return 0;
}

+static int
+icm_icl_driver_ready(struct tb *tb, enum tb_security_level *security_level,
+ size_t *nboot_acl, bool *rpm)
+{
+ struct icm_tr_pkg_driver_ready_response reply;
+ struct icm_pkg_driver_ready request = {
+ .hdr.code = ICM_DRIVER_READY,
+ };
+ int ret;
+
+ memset(&reply, 0, sizeof(reply));
+ ret = icm_request(tb, &request, sizeof(request), &reply, sizeof(reply),
+ 1, 20000);
+ if (ret)
+ return ret;
+
+ /* Ice Lake always supports RTD3 */
+ if (rpm)
+ *rpm = true;
+
+ return 0;
+}
+
+static void icm_icl_set_uuid(struct tb *tb)
+{
+ struct tb_nhi *nhi = tb->nhi;
+ u32 uuid[4];
+
+ pci_read_config_dword(nhi->pdev, VS_CAP_10, &uuid[0]);
+ pci_read_config_dword(nhi->pdev, VS_CAP_11, &uuid[1]);
+ uuid[2] = 0xffffffff;
+ uuid[3] = 0xffffffff;
+
+ tb->root_switch->uuid = kmemdup(uuid, sizeof(uuid), GFP_KERNEL);
+}
+
+static void
+icm_icl_device_connected(struct tb *tb, const struct icm_pkg_header *hdr)
+{
+ __icm_tr_device_connected(tb, hdr, true);
+}
+
+static void icm_icl_rtd3_veto(struct tb *tb, const struct icm_pkg_header *hdr)
+{
+ const struct icm_icl_event_rtd3_veto *pkg =
+ (const struct icm_icl_event_rtd3_veto *)hdr;
+ struct icm *icm = tb_priv(tb);
+
+ tb_dbg(tb, "ICM rtd3 veto=0x%08x\n", pkg->veto_reason);
+
+ if (pkg->veto_reason) {
+ if (!icm->veto) {
+ icm->veto = true;
+ /* Keep the domain powered while veto is in effect */
+ pm_runtime_get(&tb->dev);
+ }
+ } else {
+ if (icm->veto) {
+ icm->veto = false;
+ /* Allow the domain suspend now */
+ pm_runtime_mark_last_busy(&tb->dev);
+ pm_runtime_put_autosuspend(&tb->dev);
+ }
+ }
+}
+
static void icm_handle_notification(struct work_struct *work)
{
struct icm_notification *n = container_of(work, typeof(*n), work);
@@ -1495,6 +1582,9 @@ static void icm_handle_notification(struct work_struct *work)
case ICM_EVENT_XDOMAIN_DISCONNECTED:
icm->xdomain_disconnected(tb, n->pkg);
break;
+ case ICM_EVENT_RTD3_VETO:
+ icm->rtd3_veto(tb, n->pkg);
+ break;
}
}

@@ -1853,6 +1943,18 @@ static void icm_complete(struct tb *tb)
if (tb->nhi->going_away)
return;

+ /*
+ * If RTD3 was vetoed before we entered system suspend allow it
+ * again now before driver ready is sent. Firmware sends a new RTD3
+ * veto if it is still the case after we have sent it driver ready
+ * command.
+ */
+ if (icm->veto) {
+ icm->veto = false;
+ pm_runtime_mark_last_busy(&tb->dev);
+ pm_runtime_put_autosuspend(&tb->dev);
+ }
+
icm_unplug_children(tb->root_switch);

/*
@@ -1918,6 +2020,9 @@ static int icm_start(struct tb *tb)
tb->root_switch->no_nvm_upgrade = !icm->can_upgrade_nvm;
tb->root_switch->rpm = icm->rpm;

+ if (icm->set_uuid)
+ icm->set_uuid(tb);
+
ret = tb_switch_add(tb->root_switch);
if (ret) {
tb_switch_put(tb->root_switch);
@@ -2002,6 +2107,19 @@ static const struct tb_cm_ops icm_tr_ops = {
.disconnect_xdomain_paths = icm_tr_disconnect_xdomain_paths,
};

+/* Ice Lake */
+static const struct tb_cm_ops icm_icl_ops = {
+ .driver_ready = icm_driver_ready,
+ .start = icm_start,
+ .stop = icm_stop,
+ .complete = icm_complete,
+ .runtime_suspend = icm_runtime_suspend,
+ .runtime_resume = icm_runtime_resume,
+ .handle_event = icm_handle_event,
+ .approve_xdomain_paths = icm_tr_approve_xdomain_paths,
+ .disconnect_xdomain_paths = icm_tr_disconnect_xdomain_paths,
+};
+
struct tb *icm_probe(struct tb_nhi *nhi)
{
struct icm *icm;
@@ -2070,6 +2188,19 @@ struct tb *icm_probe(struct tb_nhi *nhi)
icm->xdomain_disconnected = icm_tr_xdomain_disconnected;
tb->cm_ops = &icm_tr_ops;
break;
+
+ case PCI_DEVICE_ID_INTEL_ICL_NHI0:
+ case PCI_DEVICE_ID_INTEL_ICL_NHI1:
+ icm->is_supported = icm_ar_is_supported;
+ icm->driver_ready = icm_icl_driver_ready;
+ icm->set_uuid = icm_icl_set_uuid;
+ icm->device_connected = icm_icl_device_connected;
+ icm->device_disconnected = icm_tr_device_disconnected;
+ icm->xdomain_connected = icm_tr_xdomain_connected;
+ icm->xdomain_disconnected = icm_tr_xdomain_disconnected;
+ icm->rtd3_veto = icm_icl_rtd3_veto;
+ tb->cm_ops = &icm_icl_ops;
+ break;
}

if (!icm->is_supported || !icm->is_supported(tb)) {
diff --git a/drivers/thunderbolt/nhi.c b/drivers/thunderbolt/nhi.c
index 09242653da67..1af873c8127c 100644
--- a/drivers/thunderbolt/nhi.c
+++ b/drivers/thunderbolt/nhi.c
@@ -16,6 +16,8 @@
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/delay.h>
+#include <linux/property.h>
+#include <linux/suspend.h>

#include "nhi.h"
#include "nhi_regs.h"
@@ -38,6 +40,60 @@
#define MSIX_MAX_VECS 16

#define NHI_MAILBOX_TIMEOUT 500 /* ms */
+#define LC_MAILBOX_TIMEOUT 500 /* ms */
+
+enum lc_mailbox_cmd {
+ LC_GO2SX = 0x02,
+ LC_GO2SX_NO_WAKE = 0x03,
+ LC_PREPARE_FOR_RESET = 0x21,
+};
+
+/**
+ * struct tb_nhi_ops - NHI specific optional operations
+ * @force_power: Issue force power for the NHI
+ * @set_ltr: Program LTR requirement values for the NHI
+ * @lc_mailbox_cmd: Send mailbox command to the link controller
+ * @lc_mailbox_cmd_complete: Wait for the previous command to complete
+ */
+struct tb_nhi_ops {
+ int (*force_power)(struct tb_nhi *nhi, bool power);
+ void (*set_ltr)(struct tb_nhi *nhi);
+ void (*lc_mailbox_cmd)(struct tb_nhi *nhi, enum lc_mailbox_cmd cmd);
+ int (*lc_mailbox_cmd_complete)(struct tb_nhi *nhi, int timeout);
+};
+
+static inline int nhi_power_up(struct tb_nhi *nhi)
+{
+ if (nhi->ops && nhi->ops->force_power)
+ return nhi->ops->force_power(nhi, true);
+ return 0;
+}
+
+static inline int nhi_power_down(struct tb_nhi *nhi)
+{
+ if (nhi->ops && nhi->ops->force_power)
+ return nhi->ops->force_power(nhi, false);
+ return 0;
+}
+
+static inline void nhi_set_ltr(struct tb_nhi *nhi)
+{
+ if (nhi->ops && nhi->ops->set_ltr)
+ nhi->ops->set_ltr(nhi);
+}
+
+static inline void lc_mailbox_cmd(struct tb_nhi *nhi, enum lc_mailbox_cmd cmd)
+{
+ if (nhi->ops && nhi->ops->lc_mailbox_cmd)
+ nhi->ops->lc_mailbox_cmd(nhi, cmd);
+}
+
+static inline int lc_mailbox_cmd_complete(struct tb_nhi *nhi, int timeout)
+{
+ if (nhi->ops && nhi->ops->lc_mailbox_cmd_complete)
+ return nhi->ops->lc_mailbox_cmd_complete(nhi, timeout);
+ return 0;
+}

static int ring_interrupt_index(struct tb_ring *ring)
{
@@ -863,12 +919,85 @@ static irqreturn_t nhi_msi(int irq, void *data)
return IRQ_HANDLED;
}

-static int nhi_suspend_noirq(struct device *dev)
+static int nhi_device_connected(struct device *dev, void *data)
+{
+ return tb_is_switch(dev);
+}
+
+static int nhi_suspend_power_down(struct tb *tb)
+{
+ int ret;
+
+ /*
+ * If there is no device connected we need to perform an additional
+ * handshake through LC mailbox and force power down before
+ * entering D3.
+ */
+ ret = device_for_each_child(&tb->root_switch->dev, NULL,
+ nhi_device_connected);
+ if (!ret) {
+ lc_mailbox_cmd(tb->nhi, LC_PREPARE_FOR_RESET);
+ ret = lc_mailbox_cmd_complete(tb->nhi,
+ LC_MAILBOX_TIMEOUT);
+ if (ret)
+ return ret;
+
+ return nhi_power_down(tb->nhi);
+ }
+
+ return 0;
+}
+
+static int __nhi_suspend_noirq(struct device *dev, bool wakeup)
{
struct pci_dev *pdev = to_pci_dev(dev);
struct tb *tb = pci_get_drvdata(pdev);
+ int ret;
+
+ ret = tb_domain_suspend_noirq(tb);
+ if (ret)
+ return ret;
+
+ if (pm_suspend_via_firmware()) {
+ enum lc_mailbox_cmd cmd = wakeup ? LC_GO2SX : LC_GO2SX_NO_WAKE;
+
+ lc_mailbox_cmd(tb->nhi, cmd);
+ ret = lc_mailbox_cmd_complete(tb->nhi, LC_MAILBOX_TIMEOUT);
+ if (ret)
+ return ret;
+ } else {
+ ret = nhi_suspend_power_down(tb);
+ }
+
+ return ret;
+}
+
+static int nhi_suspend_noirq(struct device *dev)
+{
+ return __nhi_suspend_noirq(dev, device_may_wakeup(dev));
+}
+
+static bool nhi_wake_supported(struct pci_dev *pdev)
+{
+ u8 val;
+
+ /*
+ * If power rails are sustainable for wakeup from S4 this
+ * property is set by the BIOS.
+ */
+ if (device_property_read_u8(&pdev->dev, "WAKE_SUPPORTED", &val))
+ return !!val;
+
+ return true;
+}
+
+static int nhi_poweroff_noirq(struct device *dev)
+{
+ struct pci_dev *pdev = to_pci_dev(dev);
+ bool wakeup;

- return tb_domain_suspend_noirq(tb);
+ wakeup = device_may_wakeup(dev) && nhi_wake_supported(pdev);
+ return __nhi_suspend_noirq(dev, wakeup);
}

static void nhi_enable_int_throttling(struct tb_nhi *nhi)
@@ -891,16 +1020,23 @@ static int nhi_resume_noirq(struct device *dev)
{
struct pci_dev *pdev = to_pci_dev(dev);
struct tb *tb = pci_get_drvdata(pdev);
+ int ret;
+
+ ret = nhi_power_up(tb->nhi);
+ if (ret)
+ return ret;

/*
* Check that the device is still there. It may be that the user
* unplugged last device which causes the host controller to go
* away on PCs.
*/
- if (!pci_device_is_present(pdev))
+ if (!pci_device_is_present(pdev)) {
tb->nhi->going_away = true;
- else
+ } else {
+ nhi_set_ltr(tb->nhi);
nhi_enable_int_throttling(tb->nhi);
+ }

return tb_domain_resume_noirq(tb);
}
@@ -933,16 +1069,28 @@ static int nhi_runtime_suspend(struct device *dev)
{
struct pci_dev *pdev = to_pci_dev(dev);
struct tb *tb = pci_get_drvdata(pdev);
+ int ret;

- return tb_domain_runtime_suspend(tb);
+ ret = tb_domain_runtime_suspend(tb);
+ if (ret)
+ return ret;
+
+ return nhi_suspend_power_down(tb);
}

static int nhi_runtime_resume(struct device *dev)
{
struct pci_dev *pdev = to_pci_dev(dev);
struct tb *tb = pci_get_drvdata(pdev);
+ int ret;

+ ret = nhi_power_up(tb->nhi);
+ if (ret)
+ return ret;
+
+ nhi_set_ltr(tb->nhi);
nhi_enable_int_throttling(tb->nhi);
+
return tb_domain_runtime_resume(tb);
}

@@ -970,6 +1118,7 @@ static void nhi_shutdown(struct tb_nhi *nhi)
flush_work(&nhi->interrupt_work);
}
ida_destroy(&nhi->msix_ida);
+ nhi_power_down(nhi);
}

static int nhi_init_msi(struct tb_nhi *nhi)
@@ -1014,12 +1163,27 @@ static int nhi_init_msi(struct tb_nhi *nhi)
return 0;
}

+static bool nhi_imr_valid(struct pci_dev *pdev)
+{
+ u8 val;
+
+ if (!device_property_read_u8(&pdev->dev, "IMR_VALID", &val))
+ return !!val;
+
+ return true;
+}
+
static int nhi_probe(struct pci_dev *pdev, const struct pci_device_id *id)
{
struct tb_nhi *nhi;
struct tb *tb;
int res;

+ if (!nhi_imr_valid(pdev)) {
+ dev_warn(&pdev->dev, "firmware image not valid, aborting\n");
+ return -ENODEV;
+ }
+
res = pcim_enable_device(pdev);
if (res) {
dev_err(&pdev->dev, "cannot enable PCI device, aborting\n");
@@ -1037,6 +1201,7 @@ static int nhi_probe(struct pci_dev *pdev, const struct pci_device_id *id)
return -ENOMEM;

nhi->pdev = pdev;
+ nhi->ops = (const struct tb_nhi_ops *)id->driver_data;
/* cannot fail - table is allocated bin pcim_iomap_regions */
nhi->iobase = pcim_iomap_table(pdev)[0];
nhi->hop_count = ioread32(nhi->iobase + REG_HOP_COUNT) & 0x3ff;
@@ -1080,6 +1245,14 @@ static int nhi_probe(struct pci_dev *pdev, const struct pci_device_id *id)

dev_dbg(&nhi->pdev->dev, "NHI initialized, starting thunderbolt\n");

+ res = nhi_power_up(nhi);
+ if (res) {
+ tb_domain_put(tb);
+ return res;
+ }
+
+ nhi_set_ltr(nhi);
+
res = tb_domain_add(tb);
if (res) {
/*
@@ -1111,6 +1284,7 @@ static void nhi_remove(struct pci_dev *pdev)

tb_domain_remove(tb);
nhi_shutdown(nhi);
+ nhi_power_down(nhi);
}

/*
@@ -1129,12 +1303,98 @@ static const struct dev_pm_ops nhi_pm_ops = {
.restore_noirq = nhi_resume_noirq,
.suspend = nhi_suspend,
.freeze = nhi_suspend,
+ .poweroff_noirq = nhi_poweroff_noirq,
.poweroff = nhi_suspend,
.complete = nhi_complete,
.runtime_suspend = nhi_runtime_suspend,
.runtime_resume = nhi_runtime_resume,
};

+/* Ice Lake specific NHI operations */
+
+static int icl_nhi_force_power(struct tb_nhi *nhi, bool power)
+{
+ u32 vs_cap;
+
+ pci_read_config_dword(nhi->pdev, VS_CAP_22, &vs_cap);
+ if (power) {
+ vs_cap &= ~VS_CAP_22_DMA_DELAY_MASK;
+ vs_cap |= 0x22 << VS_CAP_22_DMA_DELAY_SHIFT;
+ vs_cap |= VS_CAP_22_FORCE_POWER;
+ } else {
+ vs_cap &= ~VS_CAP_22_FORCE_POWER;
+ }
+ pci_write_config_dword(nhi->pdev, VS_CAP_22, vs_cap);
+
+ if (power) {
+ unsigned int retries = 10;
+ u32 val;
+
+ /* Wait until the firmware tells it is up and running */
+ do {
+ pci_read_config_dword(nhi->pdev, VS_CAP_9, &val);
+ if (val & VS_CAP_9_FW_READY)
+ return 0;
+ msleep(250);
+ } while (--retries);
+
+ return -ETIMEDOUT;
+ }
+
+ return 0;
+}
+
+static void icl_nhi_set_ltr(struct tb_nhi *nhi)
+{
+ u32 max_ltr, ltr;
+
+ pci_read_config_dword(nhi->pdev, VS_CAP_16, &max_ltr);
+ max_ltr &= 0xffff;
+ /* Program the same value for both snoop and no-snoop */
+ ltr = max_ltr << 16 | max_ltr;
+ pci_write_config_dword(nhi->pdev, VS_CAP_15, ltr);
+}
+
+static void icl_nhi_lc_mailbox_cmd(struct tb_nhi *nhi, enum lc_mailbox_cmd cmd)
+{
+ u32 data;
+
+ pci_read_config_dword(nhi->pdev, VS_CAP_19, &data);
+ data = (cmd << VS_CAP_19_CMD_SHIFT) & VS_CAP_19_CMD_MASK;
+ pci_write_config_dword(nhi->pdev, VS_CAP_19, data | VS_CAP_19_VALID);
+}
+
+static int icl_nhi_lc_mailbox_cmd_complete(struct tb_nhi *nhi, int timeout)
+{
+ unsigned long end;
+ u32 data;
+
+ if (!timeout)
+ goto clear;
+
+ end = jiffies + msecs_to_jiffies(timeout);
+ do {
+ pci_read_config_dword(nhi->pdev, VS_CAP_18, &data);
+ if (data & VS_CAP_18_DONE)
+ goto clear;
+ msleep(100);
+ } while (time_before(jiffies, end));
+
+ return -ETIMEDOUT;
+
+clear:
+ /* Clear the valid bit */
+ pci_write_config_dword(nhi->pdev, VS_CAP_19, 0);
+ return 0;
+}
+
+static const struct tb_nhi_ops icl_nhi_ops = {
+ .force_power = icl_nhi_force_power,
+ .set_ltr = icl_nhi_set_ltr,
+ .lc_mailbox_cmd = icl_nhi_lc_mailbox_cmd,
+ .lc_mailbox_cmd_complete = icl_nhi_lc_mailbox_cmd_complete,
+};
+
static struct pci_device_id nhi_ids[] = {
/*
* We have to specify class, the TB bridges use the same device and
@@ -1176,6 +1436,10 @@ static struct pci_device_id nhi_ids[] = {
{ PCI_VDEVICE(INTEL, PCI_DEVICE_ID_INTEL_ALPINE_RIDGE_C_USBONLY_NHI) },
{ PCI_VDEVICE(INTEL, PCI_DEVICE_ID_INTEL_TITAN_RIDGE_2C_NHI) },
{ PCI_VDEVICE(INTEL, PCI_DEVICE_ID_INTEL_TITAN_RIDGE_4C_NHI) },
+ { PCI_VDEVICE(INTEL, PCI_DEVICE_ID_INTEL_ICL_NHI0),
+ .driver_data = (kernel_ulong_t)&icl_nhi_ops },
+ { PCI_VDEVICE(INTEL, PCI_DEVICE_ID_INTEL_ICL_NHI1),
+ .driver_data = (kernel_ulong_t)&icl_nhi_ops },

{ 0,}
};
diff --git a/drivers/thunderbolt/nhi.h b/drivers/thunderbolt/nhi.h
index 1b5d47ecd3ed..dad691d1b704 100644
--- a/drivers/thunderbolt/nhi.h
+++ b/drivers/thunderbolt/nhi.h
@@ -51,5 +51,7 @@ enum nhi_fw_mode nhi_mailbox_mode(struct tb_nhi *nhi);
#define PCI_DEVICE_ID_INTEL_TITAN_RIDGE_4C_BRIDGE 0x15ea
#define PCI_DEVICE_ID_INTEL_TITAN_RIDGE_4C_NHI 0x15eb
#define PCI_DEVICE_ID_INTEL_TITAN_RIDGE_DD_BRIDGE 0x15ef
+#define PCI_DEVICE_ID_INTEL_ICL_NHI1 0x8a0d
+#define PCI_DEVICE_ID_INTEL_ICL_NHI0 0x8a17

#endif
diff --git a/drivers/thunderbolt/nhi_regs.h b/drivers/thunderbolt/nhi_regs.h
index a60bd98c1d04..8754e7dd63d5 100644
--- a/drivers/thunderbolt/nhi_regs.h
+++ b/drivers/thunderbolt/nhi_regs.h
@@ -124,4 +124,29 @@ struct ring_desc {
#define REG_FW_STS_ICM_EN_INVERT BIT(1)
#define REG_FW_STS_ICM_EN BIT(0)

+/* ICL NHI VSEC registers */
+
+/* FW ready */
+#define VS_CAP_9 0xc8
+#define VS_CAP_9_FW_READY BIT(31)
+/* UUID */
+#define VS_CAP_10 0xcc
+#define VS_CAP_11 0xd0
+/* LTR */
+#define VS_CAP_15 0xe0
+#define VS_CAP_16 0xe4
+/* TBT2PCIe */
+#define VS_CAP_18 0xec
+#define VS_CAP_18_DONE BIT(0)
+/* PCIe2TBT */
+#define VS_CAP_19 0xf0
+#define VS_CAP_19_VALID BIT(0)
+#define VS_CAP_19_CMD_SHIFT 1
+#define VS_CAP_19_CMD_MASK GENMASK(7, 1)
+/* Force power */
+#define VS_CAP_22 0xfc
+#define VS_CAP_22_FORCE_POWER BIT(1)
+#define VS_CAP_22_DMA_DELAY_MASK GENMASK(31, 24)
+#define VS_CAP_22_DMA_DELAY_SHIFT 24
+
#endif
diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index e318e9714a38..b896aa78fa9f 100644
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -1470,6 +1470,8 @@ static int tb_switch_get_generation(struct tb_switch *sw)
case PCI_DEVICE_ID_INTEL_TITAN_RIDGE_2C_BRIDGE:
case PCI_DEVICE_ID_INTEL_TITAN_RIDGE_4C_BRIDGE:
case PCI_DEVICE_ID_INTEL_TITAN_RIDGE_DD_BRIDGE:
+ case PCI_DEVICE_ID_INTEL_ICL_NHI0:
+ case PCI_DEVICE_ID_INTEL_ICL_NHI1:
return 3;

default:
diff --git a/drivers/thunderbolt/tb_msgs.h b/drivers/thunderbolt/tb_msgs.h
index afbe1d29bb03..4b641e4ee0c5 100644
--- a/drivers/thunderbolt/tb_msgs.h
+++ b/drivers/thunderbolt/tb_msgs.h
@@ -104,10 +104,11 @@ enum icm_pkg_code {
};

enum icm_event_code {
- ICM_EVENT_DEVICE_CONNECTED = 3,
- ICM_EVENT_DEVICE_DISCONNECTED = 4,
- ICM_EVENT_XDOMAIN_CONNECTED = 6,
- ICM_EVENT_XDOMAIN_DISCONNECTED = 7,
+ ICM_EVENT_DEVICE_CONNECTED = 0x3,
+ ICM_EVENT_DEVICE_DISCONNECTED = 0x4,
+ ICM_EVENT_XDOMAIN_CONNECTED = 0x6,
+ ICM_EVENT_XDOMAIN_DISCONNECTED = 0x7,
+ ICM_EVENT_RTD3_VETO = 0xa,
};

struct icm_pkg_header {
@@ -463,6 +464,13 @@ struct icm_tr_pkg_disconnect_xdomain_response {
uuid_t remote_uuid;
};

+/* Ice Lake messages */
+
+struct icm_icl_event_rtd3_veto {
+ struct icm_pkg_header hdr;
+ u32 veto_reason;
+};
+
/* XDomain messages */

struct tb_xdomain_header {
diff --git a/include/linux/thunderbolt.h b/include/linux/thunderbolt.h
index 2d7e012db03f..ece782ef5466 100644
--- a/include/linux/thunderbolt.h
+++ b/include/linux/thunderbolt.h
@@ -429,6 +429,7 @@ static inline struct tb_xdomain *tb_service_parent(struct tb_service *svc)
* @lock: Must be held during ring creation/destruction. Is acquired by
* interrupt_work when dispatching interrupts to individual rings.
* @pdev: Pointer to the PCI device
+ * @ops: NHI specific optional ops
* @iobase: MMIO space of the NHI
* @tx_rings: All Tx rings available on this host controller
* @rx_rings: All Rx rings available on this host controller
@@ -442,6 +443,7 @@ static inline struct tb_xdomain *tb_service_parent(struct tb_service *svc)
struct tb_nhi {
spinlock_t lock;
struct pci_dev *pdev;
+ const struct tb_nhi_ops *ops;
void __iomem *iobase;
struct tb_ring **tx_rings;
struct tb_ring **rx_rings;
--
2.20.1


2019-07-05 14:49:16

by Yehezkel Bernat

[permalink] [raw]
Subject: Re: [PATCH 7/8] thunderbolt: Add support for Intel Ice Lake

On Fri, Jul 5, 2019 at 12:58 PM Mika Westerberg
<[email protected]> wrote:
>
> +static void icm_icl_rtd3_veto(struct tb *tb, const struct icm_pkg_header *hdr)
> +{
> + const struct icm_icl_event_rtd3_veto *pkg =
> + (const struct icm_icl_event_rtd3_veto *)hdr;
> + struct icm *icm = tb_priv(tb);
> +
> + tb_dbg(tb, "ICM rtd3 veto=0x%08x\n", pkg->veto_reason);
> +
> + if (pkg->veto_reason) {
> + if (!icm->veto) {
> + icm->veto = true;
> + /* Keep the domain powered while veto is in effect */
> + pm_runtime_get(&tb->dev);
> + }
> + } else {
> + if (icm->veto) {
> + icm->veto = false;
> + /* Allow the domain suspend now */
> + pm_runtime_mark_last_busy(&tb->dev);
> + pm_runtime_put_autosuspend(&tb->dev);

Handling the removal of the veto is duplicated below. Worth introducing as a
helper function?

> + }
> + }
> +}
> +

...

> @@ -1853,6 +1943,18 @@ static void icm_complete(struct tb *tb)
> if (tb->nhi->going_away)
> return;
>
> + /*
> + * If RTD3 was vetoed before we entered system suspend allow it
> + * again now before driver ready is sent. Firmware sends a new RTD3
> + * veto if it is still the case after we have sent it driver ready
> + * command.
> + */
> + if (icm->veto) {
> + icm->veto = false;
> + pm_runtime_mark_last_busy(&tb->dev);
> + pm_runtime_put_autosuspend(&tb->dev);
> + }
> +

Here is the duplication.


> +static int nhi_suspend_power_down(struct tb *tb)
> +{
> + int ret;
> +
> + /*
> + * If there is no device connected we need to perform an additional
> + * handshake through LC mailbox and force power down before
> + * entering D3.
> + */
> + ret = device_for_each_child(&tb->root_switch->dev, NULL,
> + nhi_device_connected);
> + if (!ret) {
> + lc_mailbox_cmd(tb->nhi, LC_PREPARE_FOR_RESET);
> + ret = lc_mailbox_cmd_complete(tb->nhi,
> + LC_MAILBOX_TIMEOUT);
> + if (ret)
> + return ret;
> +
> + return nhi_power_down(tb->nhi);

Just to be sure: unforce power is done only if no device is connected?
My understanding of the comment above was that unforce power should be done
anyway (so it should be outside of this if block), and the difference between
the cases is only about the additional LC mailbox message. I guess I misread it.

> + }
> +
> + return 0;
> +}
> +

2019-07-05 14:53:44

by Mika Westerberg

[permalink] [raw]
Subject: Re: [PATCH 7/8] thunderbolt: Add support for Intel Ice Lake

On Fri, Jul 05, 2019 at 05:44:01PM +0300, Yehezkel Bernat wrote:
> On Fri, Jul 5, 2019 at 12:58 PM Mika Westerberg
> <[email protected]> wrote:
> >
> > +static void icm_icl_rtd3_veto(struct tb *tb, const struct icm_pkg_header *hdr)
> > +{
> > + const struct icm_icl_event_rtd3_veto *pkg =
> > + (const struct icm_icl_event_rtd3_veto *)hdr;
> > + struct icm *icm = tb_priv(tb);
> > +
> > + tb_dbg(tb, "ICM rtd3 veto=0x%08x\n", pkg->veto_reason);
> > +
> > + if (pkg->veto_reason) {
> > + if (!icm->veto) {
> > + icm->veto = true;
> > + /* Keep the domain powered while veto is in effect */
> > + pm_runtime_get(&tb->dev);
> > + }
> > + } else {
> > + if (icm->veto) {
> > + icm->veto = false;
> > + /* Allow the domain suspend now */
> > + pm_runtime_mark_last_busy(&tb->dev);
> > + pm_runtime_put_autosuspend(&tb->dev);
>
> Handling the removal of the veto is duplicated below. Worth introducing as a
> helper function?
>
> > + }
> > + }
> > +}
> > +
>
> ...
>
> > @@ -1853,6 +1943,18 @@ static void icm_complete(struct tb *tb)
> > if (tb->nhi->going_away)
> > return;
> >
> > + /*
> > + * If RTD3 was vetoed before we entered system suspend allow it
> > + * again now before driver ready is sent. Firmware sends a new RTD3
> > + * veto if it is still the case after we have sent it driver ready
> > + * command.
> > + */
> > + if (icm->veto) {
> > + icm->veto = false;
> > + pm_runtime_mark_last_busy(&tb->dev);
> > + pm_runtime_put_autosuspend(&tb->dev);
> > + }
> > +
>
> Here is the duplication.

Indeed, I'll put it to a helper function.

> > +static int nhi_suspend_power_down(struct tb *tb)
> > +{
> > + int ret;
> > +
> > + /*
> > + * If there is no device connected we need to perform an additional
> > + * handshake through LC mailbox and force power down before
> > + * entering D3.
> > + */
> > + ret = device_for_each_child(&tb->root_switch->dev, NULL,
> > + nhi_device_connected);
> > + if (!ret) {
> > + lc_mailbox_cmd(tb->nhi, LC_PREPARE_FOR_RESET);
> > + ret = lc_mailbox_cmd_complete(tb->nhi,
> > + LC_MAILBOX_TIMEOUT);
> > + if (ret)
> > + return ret;
> > +
> > + return nhi_power_down(tb->nhi);
>
> Just to be sure: unforce power is done only if no device is connected?
> My understanding of the comment above was that unforce power should be done
> anyway (so it should be outside of this if block), and the difference between
> the cases is only about the additional LC mailbox message. I guess I misread it.

nhi_power_down() should be only called if no device was connected so it
should be in correct place. I can try to clarify the comment a bit,
though.

2019-07-05 15:04:48

by Yehezkel Bernat

[permalink] [raw]
Subject: Re: [PATCH 7/8] thunderbolt: Add support for Intel Ice Lake

On Fri, Jul 5, 2019 at 5:51 PM Mika Westerberg
<[email protected]> wrote:
>
> > > +static int nhi_suspend_power_down(struct tb *tb)
> > > +{
> > > + int ret;
> > > +
> > > + /*
> > > + * If there is no device connected we need to perform an additional
> > > + * handshake through LC mailbox and force power down before
> > > + * entering D3.
> > > + */
> > > + ret = device_for_each_child(&tb->root_switch->dev, NULL,
> > > + nhi_device_connected);
> > > + if (!ret) {
> > > + lc_mailbox_cmd(tb->nhi, LC_PREPARE_FOR_RESET);
> > > + ret = lc_mailbox_cmd_complete(tb->nhi,
> > > + LC_MAILBOX_TIMEOUT);
> > > + if (ret)
> > > + return ret;
> > > +
> > > + return nhi_power_down(tb->nhi);
> >
> > Just to be sure: unforce power is done only if no device is connected?
> > My understanding of the comment above was that unforce power should be done
> > anyway (so it should be outside of this if block), and the difference between
> > the cases is only about the additional LC mailbox message. I guess I misread it.
>
> nhi_power_down() should be only called if no device was connected so it
> should be in correct place. I can try to clarify the comment a bit,
> though.

Maybe adding the word "both" ("to perform both an additional") will make it
clearer. Maybe removing the "additional" (which to my ears sounds like "an
additional operation besides the normal one, to unforce power") is enough.
Again, your call. I'm not sure it's strictly needed, maybe it's just me.

Thanks!

2019-08-04 18:26:38

by Lukas Wunner

[permalink] [raw]
Subject: Re: [PATCH 7/8] thunderbolt: Add support for Intel Ice Lake

On Fri, Jul 05, 2019 at 12:57:59PM +0300, Mika Westerberg wrote:
> @@ -891,16 +1020,23 @@ static int nhi_resume_noirq(struct device *dev)
> {
> struct pci_dev *pdev = to_pci_dev(dev);
> struct tb *tb = pci_get_drvdata(pdev);
> + int ret;
> +
> + ret = nhi_power_up(tb->nhi);

Some general thoughts:

You're enabling Force Power during the resume_noirq phase of the NHI.

If TBT devices were already connected before system sleep, the PCI core
walks down the hierarchy during resume_noirq, puts each device into D0 and
restores config space. For this to work, the NHI must have set up tunnels
to attached devices. But it can hardly do that until Force Power is
enabled. Yet I cannot see any provision here which causes the hotplug
bridges to wait for the NHI to finish its resume_noirq phase.

Don't you need that?

On Macs we have quirk_apple_wait_for_thunderbolt() to resolve this issue.

And a commit has been rotting on my development branch for years
which replaces quirk_apple_wait_for_thunderbolt() with device links:

https://github.com/l1k/linux/commit/8cbb1d589660


Also, you recently posted a patch stating that on Ice Lake, the NHI and
hotplug bridges share an ACPI Power Resource:

https://patchwork.kernel.org/patch/11015233/

How does that relate to the Force Power and Go2Sx dance implemented in
the present patch? Does the ACPI Power Resource toggle the same Force
Power and Go2Sx registers as this patch here? Or is that an additional
power management mechanism? If Force Power is off on the NHI, are the
hotplug bridges' config and mmio spaces accessible? All of this should
be documented in code comments or at least the commit message.


There's a quirk for Macs with Cactus Ridge to perform a Go2Sx dance
during the suspend_noirq phase, quirk_apple_poweroff_thunderbolt().
Can this be reimplemented using the infrastructure you're adding
in this patch?


On Macs with Thunderbolt 1 and 2, there are ACPI methods to toggle
Force Power in the NHI's namespace. However disabling Force Power
not only cuts power to the NHI but also to the integrated PCIe switch.
For this reason, I've implemented power management on these Macs using
a struct dev_pm_domain which is assigned to the upstream bridge of
the integrated PCIe switch. That way, power isn't cut until the
Thunderbolt controller's top-most device in the hierarchy is runtime
suspended:

https://github.com/l1k/linux/commit/4db7f0b1f5c9

I'm wondering if it would make sense to similarly assign a dev_pm_domain
to the NHI on Ice Lake.


One thing that bothers me a bit with the present patch is that nhi.c
is cluttered up with code specific to Ice Lake. That doesn't seem
sustainable going forward as I expect we'll have to add plenty of
other quirks once USB4 chipsets become available. Ideally the file
should contain only (or mostly) generic code and quirks should be
contained in separate files which need not be compiled in on
unrelated arches. That's why in the above-linked commit to add
Apple-specific power management, I put all the code in a pm_apple.c
and nhi.c only calls tb_pm_apple_init() / _fini(), which become
empty inline stubs if CONFIG_ACPI or CONFIG_PM isn't enabled.


> --- a/drivers/thunderbolt/nhi.c
> +++ b/drivers/thunderbolt/nhi.c
> @@ -38,6 +40,60 @@
> #define MSIX_MAX_VECS 16
>
> #define NHI_MAILBOX_TIMEOUT 500 /* ms */
> +#define LC_MAILBOX_TIMEOUT 500 /* ms */
> +
> +enum lc_mailbox_cmd {
> + LC_GO2SX = 0x02,
> + LC_GO2SX_NO_WAKE = 0x03,
> + LC_PREPARE_FOR_RESET = 0x21,
> +};

Shouldn't these live together with the other LC macros in tb_regs.h?


> + ret = device_for_each_child(&tb->root_switch->dev, NULL,
> + nhi_device_connected);
> + if (!ret) {
> + lc_mailbox_cmd(tb->nhi, LC_PREPARE_FOR_RESET);
> + ret = lc_mailbox_cmd_complete(tb->nhi,
> + LC_MAILBOX_TIMEOUT);
> + if (ret)
> + return ret;
> +
> + return nhi_power_down(tb->nhi);
> + }
> +
> + return 0;
> +}

Why not:

if (ret)
return 0;

and that way reduce the indentation of the code in your if-block by 1 tab?

Thanks,

Lukas

2019-08-05 14:17:34

by Mika Westerberg

[permalink] [raw]
Subject: Re: [PATCH 7/8] thunderbolt: Add support for Intel Ice Lake

On Sun, Aug 04, 2019 at 08:25:10PM +0200, Lukas Wunner wrote:
> On Fri, Jul 05, 2019 at 12:57:59PM +0300, Mika Westerberg wrote:
> > @@ -891,16 +1020,23 @@ static int nhi_resume_noirq(struct device *dev)
> > {
> > struct pci_dev *pdev = to_pci_dev(dev);
> > struct tb *tb = pci_get_drvdata(pdev);
> > + int ret;
> > +
> > + ret = nhi_power_up(tb->nhi);
>
> Some general thoughts:
>
> You're enabling Force Power during the resume_noirq phase of the NHI.
>
> If TBT devices were already connected before system sleep, the PCI core
> walks down the hierarchy during resume_noirq, puts each device into D0 and
> restores config space. For this to work, the NHI must have set up tunnels
> to attached devices. But it can hardly do that until Force Power is
> enabled. Yet I cannot see any provision here which causes the hotplug
> bridges to wait for the NHI to finish its resume_noirq phase.
>
> Don't you need that?

For the FW CM we don't because there is some magic ASL as part of the
ACPI power resources (shared between root ports and NHI) that causes the
firmware to establish tunnels as part of _ON() method.

> On Macs we have quirk_apple_wait_for_thunderbolt() to resolve this issue.
>
> And a commit has been rotting on my development branch for years
> which replaces quirk_apple_wait_for_thunderbolt() with device links:
>
> https://github.com/l1k/linux/commit/8cbb1d589660
>
>
> Also, you recently posted a patch stating that on Ice Lake, the NHI and
> hotplug bridges share an ACPI Power Resource:
>
> https://patchwork.kernel.org/patch/11015233/
>
> How does that relate to the Force Power and Go2Sx dance implemented in
> the present patch? Does the ACPI Power Resource toggle the same Force
> Power and Go2Sx registers as this patch here? Or is that an additional
> power management mechanism?

It is an additional mechanism (but I think it also touches force power
at some point). Force power here is not the same as with the discrete
chips. AFAIK it pretty much only loads and starts the firmware whereas
in discrete it actually controls power to the chip.

> If Force Power is off on the NHI, are the hotplug bridges' config and
> mmio spaces accessible?

Yes, they are all accessible.

> All of this should be documented in code comments or at least the
> commit message.

Will do.

> There's a quirk for Macs with Cactus Ridge to perform a Go2Sx dance
> during the suspend_noirq phase, quirk_apple_poweroff_thunderbolt().
> Can this be reimplemented using the infrastructure you're adding
> in this patch?

It might be possible to implement ->force_power for Cactus Ridge and do
the ACPI magic there instead. I'll try and see what it looks like.

> On Macs with Thunderbolt 1 and 2, there are ACPI methods to toggle
> Force Power in the NHI's namespace. However disabling Force Power
> not only cuts power to the NHI but also to the integrated PCIe switch.
> For this reason, I've implemented power management on these Macs using
> a struct dev_pm_domain which is assigned to the upstream bridge of
> the integrated PCIe switch. That way, power isn't cut until the
> Thunderbolt controller's top-most device in the hierarchy is runtime
> suspended:
>
> https://github.com/l1k/linux/commit/4db7f0b1f5c9
>
> I'm wondering if it would make sense to similarly assign a dev_pm_domain
> to the NHI on Ice Lake.

Using PM domain here does not feel right to me. The force power thing
here is not really about power (but I'm calling it that because that's
the what we use internally) so I think it should be part of normal
driver flows.

> One thing that bothers me a bit with the present patch is that nhi.c
> is cluttered up with code specific to Ice Lake. That doesn't seem
> sustainable going forward as I expect we'll have to add plenty of
> other quirks once USB4 chipsets become available. Ideally the file
> should contain only (or mostly) generic code and quirks should be
> contained in separate files which need not be compiled in on
> unrelated arches.

I originally intented to have ICL support in icm.c but I realized that
the same steps are most likely needed on Apple systems as well (I don't
have any so can't tell if that's really the case) and since these flows
are for the NHI I figured that's the correct place for it.

I agree with you that moving chip specific things to separate files
makes sense (such as icl.c and so on) in the long run to keep the driver
maintainable.

> That's why in the above-linked commit to add
> Apple-specific power management, I put all the code in a pm_apple.c
> and nhi.c only calls tb_pm_apple_init() / _fini(), which become
> empty inline stubs if CONFIG_ACPI or CONFIG_PM isn't enabled.
>
>
> > --- a/drivers/thunderbolt/nhi.c
> > +++ b/drivers/thunderbolt/nhi.c
> > @@ -38,6 +40,60 @@
> > #define MSIX_MAX_VECS 16
> >
> > #define NHI_MAILBOX_TIMEOUT 500 /* ms */
> > +#define LC_MAILBOX_TIMEOUT 500 /* ms */
> > +
> > +enum lc_mailbox_cmd {
> > + LC_GO2SX = 0x02,
> > + LC_GO2SX_NO_WAKE = 0x03,
> > + LC_PREPARE_FOR_RESET = 0x21,
> > +};
>
> Shouldn't these live together with the other LC macros in tb_regs.h?

I've used tb_regs.h to keep registers and definitions that belong to
Thunderbolt fabric. The other LC macros are there because they are used
to access LC over TBT.

Here we access it through NHI and only use it in nhi.c.

No strong feelings moving it to tb_regs.h if you still think that's
more suitable.

> > + ret = device_for_each_child(&tb->root_switch->dev, NULL,
> > + nhi_device_connected);
> > + if (!ret) {
> > + lc_mailbox_cmd(tb->nhi, LC_PREPARE_FOR_RESET);
> > + ret = lc_mailbox_cmd_complete(tb->nhi,
> > + LC_MAILBOX_TIMEOUT);
> > + if (ret)
> > + return ret;
> > +
> > + return nhi_power_down(tb->nhi);
> > + }
> > +
> > + return 0;
> > +}
>
> Why not:
>
> if (ret)
> return 0;
>
> and that way reduce the indentation of the code in your if-block by 1 tab?

Indeed. Will do.