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From:   Frank Li <Frank.Li@nxp.com>
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Subject: [PATCH v6 1/2] PCI: dwc: Implement general suspend/resume functionality for L2/L3 transitions
Date:   Mon, 31 Jul 2023 15:40:09 -0400
Message-Id: <20230731194010.73016-1-Frank.Li@nxp.com>
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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
handle.

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.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Change from v5 to v6:
- refine commit message
  change according to Manivannan's comments.
  - remove reduncate step dw_pcie_set_dstate()
  - return 0 when .pme_turn_off is zero
  - call host_deinit() in suspend
  - check .host_deinit and .host_init point before call.

Change from v4 to v5:
- Closes: https://lore.kernel.org/oe-kbuild-all/202307211904.zExw4Q8H-lkp@intel.com/
Change from v3 to v4:
- change according to Manivannan's comments.
  I hope I have not missed anything. quite long discuss thread
Change from v2 to v3:
- Basic rewrite whole patch according rob herry suggestion.
  put common function into dwc, so more soc can share the same logic.

 .../pci/controller/dwc/pcie-designware-host.c | 78 +++++++++++++++++++
 drivers/pci/controller/dwc/pcie-designware.h  | 28 +++++++
 2 files changed, 106 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 9952057c8819c..1822c04d370b2 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>
@@ -807,3 +808,80 @@ 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);
+
+	/*
+	 * PCI Express Base Specification Rev 4.0 5.3.3.2.1 PME Synchronization
+	 * Recommands 1ms to 10ms timeout to check L2 ready
+	 */
+	ret = read_poll_timeout(dw_pcie_get_ltssm, val, val == DW_PCIE_LTSSM_L2_IDLE,
+				100, 10000, 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! ret = 0x%x\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..cbba3ed19b3c0 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -288,10 +288,21 @@ enum dw_pcie_core_rst {
 	DW_PCIE_NUM_CORE_RSTS
 };
 
+enum dw_pcie_ltssm {
+	DW_PCIE_LTSSM_UNKNOWN = 0xFFFFFFFF,
+	/* 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,
+};
+
 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 +375,7 @@ 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 +405,7 @@ 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 +443,9 @@ 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 +517,18 @@ 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