[PATCH v11 2/3] PCI: dwc: Implement general suspend/resume functionality for L2/L3 transitions

Frank Li
2023-08-09T15:37:32Z

Introduce helper function dw_pcie_get_ltssm() to retrieve SMLH_LTSS_STATE.

Add callback .pme_turn_off and .exit_from_l2 for platform specific PME
handling.

Add common dw_pcie_suspend(resume)_noirq() API to avoid duplicated code
in dwc pci host controller platform driver.

Typical L2 entry workflow/dw_pcie_suspend_noirq()

1. Transmit PME turn off signal to PCI devices and wait for PME_To_Ack.
2. Await link entering L2_IDLE state.

Typical L2 exit workflow/dw_pcie_resume_noirq()

1. Issue exit from L2 command.
2. Reinitialize PCI host.
3. Wait for link to become active.

Acked-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
.../pci/controller/dwc/pcie-designware-host.c | 76 +++++++++++++++++++
drivers/pci/controller/dwc/pcie-designware.h | 29 +++++++
2 files changed, 105 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 9952057c8819c..cdbff11a7d00e 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -8,6 +8,7 @@
* Author: Jingoo Han <jg1.han@samsung.com>
*/

+#include <linux/iopoll.h>
#include <linux/irqchip/chained_irq.h>
#include <linux/irqdomain.h>
#include <linux/msi.h>
@@ -16,6 +17,7 @@
#include <linux/pci_regs.h>
#include <linux/platform_device.h>

+#include "../../pci.h"
#include "pcie-designware.h"

static struct pci_ops dw_pcie_ops;
@@ -807,3 +809,77 @@ int dw_pcie_setup_rc(struct dw_pcie_rp *pp)
return 0;
}
EXPORT_SYMBOL_GPL(dw_pcie_setup_rc);
+
+int dw_pcie_suspend_noirq(struct dw_pcie *pci)
+{
+ u8 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
+ u32 val;
+ int ret;
+
+ /*
+ * If L1SS is supported, then do not put the link into L2 as some
+ * devices such as NVMe expect low resume latency.
+ */
+ if (dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKCTL) & PCI_EXP_LNKCTL_ASPM_L1)
+ return 0;
+
+ if (dw_pcie_get_ltssm(pci) <= DW_PCIE_LTSSM_DETECT_ACT)
+ return 0;
+
+ if (!pci->pp.ops->pme_turn_off)
+ return 0;
+
+ pci->pp.ops->pme_turn_off(&pci->pp);
+
+ ret = read_poll_timeout(dw_pcie_get_ltssm, val, val == DW_PCIE_LTSSM_L2_IDLE,
+ PCIE_PME_TO_L2_TIMEOUT_US/10,
+ PCIE_PME_TO_L2_TIMEOUT_US, false, pci);
+ if (ret) {
+ dev_err(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val);
+ return ret;
+ }
+
+ if (pci->pp.ops->host_deinit)
+ pci->pp.ops->host_deinit(&pci->pp);
+
+ pci->suspended = true;
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dw_pcie_suspend_noirq);
+
+int dw_pcie_resume_noirq(struct dw_pcie *pci)
+{
+ int ret;
+
+ if (!pci->suspended)
+ return 0;
+
+ pci->suspended = false;
+
+ if (!pci->pp.ops->exit_from_l2)
+ return 0;
+
+ pci->pp.ops->exit_from_l2(&pci->pp);
+
+ if (pci->pp.ops->host_init) {
+ ret = pci->pp.ops->host_init(&pci->pp);
+ if (ret) {
+ dev_err(pci->dev, "Host init failed: %d\n", ret);
+ return ret;
+ }
+ }
+
+ dw_pcie_setup_rc(&pci->pp);
+
+ ret = dw_pcie_start_link(pci);
+ if (ret)
+ return ret;
+
+ ret = dw_pcie_wait_for_link(pci);
+ if (ret)
+ return ret;
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dw_pcie_resume_noirq);
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 79713ce075cc1..629bccfa92ddd 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -288,10 +288,22 @@ enum dw_pcie_core_rst {
DW_PCIE_NUM_CORE_RSTS
};

+enum dw_pcie_ltssm {
+ /* Need to align with PCIE_PORT_DEBUG0 bits 0:5 */
+ DW_PCIE_LTSSM_DETECT_QUIET = 0x0,
+ DW_PCIE_LTSSM_DETECT_ACT = 0x1,
+ DW_PCIE_LTSSM_L0 = 0x11,
+ DW_PCIE_LTSSM_L2_IDLE = 0x15,
+
+ DW_PCIE_LTSSM_UNKNOWN = 0xFFFFFFFF,
+};
+
struct dw_pcie_host_ops {
int (*host_init)(struct dw_pcie_rp *pp);
void (*host_deinit)(struct dw_pcie_rp *pp);
int (*msi_host_init)(struct dw_pcie_rp *pp);
+ void (*pme_turn_off)(struct dw_pcie_rp *pp);
+ void (*exit_from_l2)(struct dw_pcie_rp *pp);
};

struct dw_pcie_rp {
@@ -364,6 +376,7 @@ struct dw_pcie_ops {
void (*write_dbi2)(struct dw_pcie *pcie, void __iomem *base, u32 reg,
size_t size, u32 val);
int (*link_up)(struct dw_pcie *pcie);
+ enum dw_pcie_ltssm (*get_ltssm)(struct dw_pcie *pcie);
int (*start_link)(struct dw_pcie *pcie);
void (*stop_link)(struct dw_pcie *pcie);
};
@@ -393,6 +406,7 @@ struct dw_pcie {
struct reset_control_bulk_data app_rsts[DW_PCIE_NUM_APP_RSTS];
struct reset_control_bulk_data core_rsts[DW_PCIE_NUM_CORE_RSTS];
struct gpio_desc *pe_rst;
+ bool suspended;
};

#define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie, pp)
@@ -430,6 +444,9 @@ void dw_pcie_iatu_detect(struct dw_pcie *pci);
int dw_pcie_edma_detect(struct dw_pcie *pci);
void dw_pcie_edma_remove(struct dw_pcie *pci);

+int dw_pcie_suspend_noirq(struct dw_pcie *pci);
+int dw_pcie_resume_noirq(struct dw_pcie *pci);
+
static inline void dw_pcie_writel_dbi(struct dw_pcie *pci, u32 reg, u32 val)
{
dw_pcie_write_dbi(pci, reg, 0x4, val);
@@ -501,6 +518,18 @@ static inline void dw_pcie_stop_link(struct dw_pcie *pci)
pci->ops->stop_link(pci);
}

+static inline enum dw_pcie_ltssm dw_pcie_get_ltssm(struct dw_pcie *pci)
+{
+ u32 val;
+
+ if (pci->ops && pci->ops->get_ltssm)
+ return pci->ops->get_ltssm(pci);
+
+ val = dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG0);
+
+ return (enum dw_pcie_ltssm)FIELD_GET(PORT_LOGIC_LTSSM_STATE_MASK, val);
+}
+
#ifdef CONFIG_PCIE_DW_HOST
irqreturn_t dw_handle_msi_irq(struct dw_pcie_rp *pp);
int dw_pcie_setup_rc(struct dw_pcie_rp *pp);
--
2.34.1