[PATCH v3 10/12] PCI: rockchip-ep: Improve link training

Damien Le Moal
2024-10-07T04:12:43Z

The Rockchip rk339 technical reference manual describe the endpoint mode
link training process clearly and states that:
Insure link training completion and success by observing link_st field
in PCIe Client BASIC_STATUS1 register change to 2'b11. If both side
support PCIe Gen2 speed, re-train can be Initiated by asserting the
Retrain Link field in Link Control and Status Register. The software
should insure the BASIC_STATUS0[negotiated_speed] changes to "1", that
indicates re-train to Gen2 successfully.
This procedure is very similar to what is done for the root-port mode in
rockchip_pcie_host_init_port().

Implement this link training procedure for the endpoint mode as well.
Given that the rk3399 SoC does not have an interrupt signaling link
status changes, training is implemented as a delayed work which is
rescheduled until the link training completes or the endpoint controller
is stopped. The link training work is first scheduled in
rockchip_pcie_ep_start() when the endpoint function is started. Link
training completion is signaled to the function using pci_epc_linkup().
Accordingly, the linkup_notifier field of the rockchip pci_epc_features
structure is changed to true.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
---
drivers/pci/controller/pcie-rockchip-ep.c | 79 ++++++++++++++++++++++-
drivers/pci/controller/pcie-rockchip.h | 11 ++++
2 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pcie-rockchip-ep.c b/drivers/pci/controller/pcie-rockchip-ep.c
index a801e040bcad..af50432525b4 100644
--- a/drivers/pci/controller/pcie-rockchip-ep.c
+++ b/drivers/pci/controller/pcie-rockchip-ep.c
@@ -16,6 +16,8 @@
#include <linux/platform_device.h>
#include <linux/pci-epf.h>
#include <linux/sizes.h>
+#include <linux/workqueue.h>
+#include <linux/iopoll.h>

#include "pcie-rockchip.h"

@@ -48,6 +50,7 @@ struct rockchip_pcie_ep {
u64 irq_pci_addr;
u8 irq_pci_fn;
u8 irq_pending;
+ struct delayed_work link_training;
};

static void rockchip_pcie_clear_ep_ob_atu(struct rockchip_pcie *rockchip,
@@ -465,6 +468,8 @@ static int rockchip_pcie_ep_start(struct pci_epc *epc)
PCIE_CLIENT_CONF_ENABLE,
PCIE_CLIENT_CONFIG);

+ schedule_delayed_work(&ep->link_training, 0);
+
return 0;
}

@@ -473,6 +478,8 @@ static void rockchip_pcie_ep_stop(struct pci_epc *epc)
struct rockchip_pcie_ep *ep = epc_get_drvdata(epc);
struct rockchip_pcie *rockchip = &ep->rockchip;

+ cancel_delayed_work_sync(&ep->link_training);
+
/* Stop link training and disable configuration */
rockchip_pcie_write(rockchip,
PCIE_CLIENT_CONF_DISABLE |
@@ -480,8 +487,77 @@ static void rockchip_pcie_ep_stop(struct pci_epc *epc)
PCIE_CLIENT_CONFIG);
}

+static void rockchip_pcie_ep_retrain_link(struct rockchip_pcie *rockchip)
+{
+ u32 status;
+
+ status = rockchip_pcie_read(rockchip, PCIE_EP_CONFIG_LCS);
+ status |= PCI_EXP_LNKCTL_RL;
+ rockchip_pcie_write(rockchip, status, PCIE_EP_CONFIG_LCS);
+}
+
+static bool rockchip_pcie_ep_link_up(struct rockchip_pcie *rockchip)
+{
+ u32 val = rockchip_pcie_read(rockchip, PCIE_CLIENT_BASIC_STATUS1);
+
+ return PCIE_LINK_UP(val);
+}
+
+static void rockchip_pcie_ep_link_training(struct work_struct *work)
+{
+ struct rockchip_pcie_ep *ep =
+ container_of(work, struct rockchip_pcie_ep, link_training.work);
+ struct rockchip_pcie *rockchip = &ep->rockchip;
+ struct device *dev = rockchip->dev;
+ u32 val;
+ int ret;
+
+ /* Enable Gen1 training and wait for its completion */
+ ret = readl_poll_timeout(rockchip->apb_base + PCIE_CORE_CTRL,
+ val, PCIE_LINK_TRAINING_DONE(val), 50,
+ LINK_TRAIN_TIMEOUT);
+ if (ret)
+ goto again;
+
+ /* Make sure that the link is up */
+ ret = readl_poll_timeout(rockchip->apb_base + PCIE_CLIENT_BASIC_STATUS1,
+ val, PCIE_LINK_UP(val), 50,
+ LINK_TRAIN_TIMEOUT);
+ if (ret)
+ goto again;
+
+ /* Check the current speed */
+ val = rockchip_pcie_read(rockchip, PCIE_CORE_CTRL);
+ if (!PCIE_LINK_IS_GEN2(val) && rockchip->link_gen == 2) {
+ /* Enable retrain for gen2 */
+ rockchip_pcie_ep_retrain_link(rockchip);
+ readl_poll_timeout(rockchip->apb_base + PCIE_CORE_CTRL,
+ val, PCIE_LINK_IS_GEN2(val), 50,
+ LINK_TRAIN_TIMEOUT);
+ }
+
+ /* Check again that the link is up */
+ if (!rockchip_pcie_ep_link_up(rockchip))
+ goto again;
+
+ val = rockchip_pcie_read(rockchip, PCIE_CLIENT_BASIC_STATUS0);
+ dev_info(dev,
+ "Link UP (Negociated speed: %sGT/s, width: x%lu)\n",
+ (val & PCIE_CLIENT_NEG_LINK_SPEED) ? "5" : "2.5",
+ ((val & PCIE_CLIENT_NEG_LINK_WIDTH_MASK) >>
+ PCIE_CLIENT_NEG_LINK_WIDTH_SHIFT) << 1);
+
+ /* Notify the function */
+ pci_epc_linkup(ep->epc);
+
+ return;
+
+again:
+ schedule_delayed_work(&ep->link_training, msecs_to_jiffies(5));
+}
+
static const struct pci_epc_features rockchip_pcie_epc_features = {
- .linkup_notifier = false,
+ .linkup_notifier = true,
.msi_capable = true,
.msix_capable = false,
.align = ROCKCHIP_PCIE_AT_SIZE_ALIGN,
@@ -642,6 +718,7 @@ static int rockchip_pcie_ep_probe(struct platform_device *pdev)
rockchip = &ep->rockchip;
rockchip->is_rc = false;
rockchip->dev = dev;
+ INIT_DELAYED_WORK(&ep->link_training, rockchip_pcie_ep_link_training);

epc = devm_pci_epc_create(dev, &rockchip_pcie_epc_ops);
if (IS_ERR(epc)) {
diff --git a/drivers/pci/controller/pcie-rockchip.h b/drivers/pci/controller/pcie-rockchip.h
index 0263f158ee8d..3963b7097a91 100644
--- a/drivers/pci/controller/pcie-rockchip.h
+++ b/drivers/pci/controller/pcie-rockchip.h
@@ -26,6 +26,7 @@
#define MAX_LANE_NUM 4
#define MAX_REGION_LIMIT 32
#define MIN_EP_APERTURE 28
+#define LINK_TRAIN_TIMEOUT (5000 * USEC_PER_MSEC)

#define PCIE_CLIENT_BASE 0x0
#define PCIE_CLIENT_CONFIG (PCIE_CLIENT_BASE + 0x00)
@@ -50,6 +51,10 @@
#define PCIE_CLIENT_DEBUG_LTSSM_MASK GENMASK(5, 0)
#define PCIE_CLIENT_DEBUG_LTSSM_L1 0x18
#define PCIE_CLIENT_DEBUG_LTSSM_L2 0x19
+#define PCIE_CLIENT_BASIC_STATUS0 (PCIE_CLIENT_BASE + 0x44)
+#define PCIE_CLIENT_NEG_LINK_WIDTH_MASK GENMASK(7, 6)
+#define PCIE_CLIENT_NEG_LINK_WIDTH_SHIFT 6
+#define PCIE_CLIENT_NEG_LINK_SPEED BIT(5)
#define PCIE_CLIENT_BASIC_STATUS1 (PCIE_CLIENT_BASE + 0x48)
#define PCIE_CLIENT_LINK_STATUS_UP 0x00300000
#define PCIE_CLIENT_LINK_STATUS_MASK 0x00300000
@@ -87,6 +92,8 @@

#define PCIE_CORE_CTRL_MGMT_BASE 0x900000
#define PCIE_CORE_CTRL (PCIE_CORE_CTRL_MGMT_BASE + 0x000)
+#define PCIE_CORE_PL_CONF_LS_MASK 0x00000001
+#define PCIE_CORE_PL_CONF_LS_READY 0x00000001
#define PCIE_CORE_PL_CONF_SPEED_5G 0x00000008
#define PCIE_CORE_PL_CONF_SPEED_MASK 0x00000018
#define PCIE_CORE_PL_CONF_LANE_MASK 0x00000006
@@ -144,6 +151,7 @@
#define PCIE_RC_CONFIG_BASE 0xa00000
#define PCIE_EP_CONFIG_BASE 0xa00000
#define PCIE_EP_CONFIG_DID_VID (PCIE_EP_CONFIG_BASE + 0x00)
+#define PCIE_EP_CONFIG_LCS (PCIE_EP_CONFIG_BASE + 0xd0)
#define PCIE_RC_CONFIG_RID_CCR (PCIE_RC_CONFIG_BASE + 0x08)
#define PCIE_RC_CONFIG_DCR (PCIE_RC_CONFIG_BASE + 0xc4)
#define PCIE_RC_CONFIG_DCR_CSPL_SHIFT 18
@@ -155,6 +163,7 @@
#define PCIE_RC_CONFIG_LINK_CAP (PCIE_RC_CONFIG_BASE + 0xcc)
#define PCIE_RC_CONFIG_LINK_CAP_L0S BIT(10)
#define PCIE_RC_CONFIG_LCS (PCIE_RC_CONFIG_BASE + 0xd0)
+#define PCIE_EP_CONFIG_LCS (PCIE_EP_CONFIG_BASE + 0xd0)
#define PCIE_RC_CONFIG_L1_SUBSTATE_CTRL2 (PCIE_RC_CONFIG_BASE + 0x90c)
#define PCIE_RC_CONFIG_THP_CAP (PCIE_RC_CONFIG_BASE + 0x274)
#define PCIE_RC_CONFIG_THP_CAP_NEXT_MASK GENMASK(31, 20)
@@ -192,6 +201,8 @@
#define ROCKCHIP_VENDOR_ID 0x1d87
#define PCIE_LINK_IS_L2(x) \
(((x) & PCIE_CLIENT_DEBUG_LTSSM_MASK) == PCIE_CLIENT_DEBUG_LTSSM_L2)
+#define PCIE_LINK_TRAINING_DONE(x) \
+ (((x) & PCIE_CORE_PL_CONF_LS_MASK) == PCIE_CORE_PL_CONF_LS_READY)
#define PCIE_LINK_UP(x) \
(((x) & PCIE_CLIENT_LINK_STATUS_MASK) == PCIE_CLIENT_LINK_STATUS_UP)
#define PCIE_LINK_IS_GEN2(x) \
--
2.46.2