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Message-ID: <20230717164526.GC35455@thinkpad>
Date: Mon, 17 Jul 2023 22:15:26 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Frank Li <Frank.Li@....com>
Cc: helgaas@...nel.org, imx@...ts.linux.dev, bhelgaas@...gle.com,
devicetree@...r.kernel.org, gustavo.pimentel@...opsys.com,
kw@...ux.com, leoyang.li@....com,
linux-arm-kernel@...ts.infradead.org, linux-imx@....com,
linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
lorenzo.pieralisi@....com, minghuan.lian@....com,
mingkai.hu@....com, robh+dt@...nel.org, roy.zang@....com,
shawnguo@...nel.org, zhiqiang.hou@....com
Subject: Re: [PATCH v3 1/2] PCI: dwc: Implement general suspend/resume
functionality for L2/L3 transitions
On Wed, Apr 19, 2023 at 12:41:17PM -0400, Frank Li wrote:
> Introduced helper function dw_pcie_get_ltssm to retrieve SMLH_LTSS_STATE.
> Added API pme_turn_off and exit_from_l2 for managing L2/L3 state transitions.
>
> Typical L2 entry workflow:
>
> 1. Transmit PME turn off signal to PCI devices.
> 2. Await link entering L2_IDLE state.
AFAIK, typical workflow is to wait for PME_To_Ack.
> 3. Transition Root complex to D3 state.
>
> Typical L2 exit workflow:
>
> 1. Transition Root complex to D0 state.
> 2. Issue exit from L2 command.
> 3. Reinitialize PCI host.
> 4. Wait for link to become active.
>
> Signed-off-by: Frank Li <Frank.Li@....com>
> ---
> 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 | 80 +++++++++++++++++++
> drivers/pci/controller/dwc/pcie-designware.h | 28 +++++++
> 2 files changed, 108 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 9952057c8819..ef6869488bde 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@...sung.com>
> */
>
> +#include <linux/iopoll.h>
> #include <linux/irqchip/chained_irq.h>
> #include <linux/irqdomain.h>
> #include <linux/msi.h>
> @@ -807,3 +808,82 @@ int dw_pcie_setup_rc(struct dw_pcie_rp *pp)
> return 0;
> }
> EXPORT_SYMBOL_GPL(dw_pcie_setup_rc);
> +
> +/*
> + * There are for configuring host controllers, which are bridges *to* PCI devices
> + * but are not PCI devices themselves.
None of the functions applicable to the devices. So there is no need for this
comment.
> + */
> +static void dw_pcie_set_dstate(struct dw_pcie *pci, u32 dstate)
Please use pci_power_t defines for dstates.
> +{
> + u8 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_PM);
> + u32 val;
> +
> + val = dw_pcie_readw_dbi(pci, offset + PCI_PM_CTRL);
Please use PCI accessors for accessing spec compliant registers.
> + val &= ~PCI_PM_CTRL_STATE_MASK;
> + val |= dstate;
> + dw_pcie_writew_dbi(pci, offset + PCI_PM_CTRL, val);
> +}
> +
> +int dw_pcie_suspend_noirq(struct dw_pcie *pci)
> +{
> + u32 val;
> + int ret;
> +
> + if (dw_pcie_get_ltssm(pci) <= DW_PCIE_LTSSM_DETECT_ACT)
> + return 0;
> +
> + pci->pp.ops->pme_turn_off(&pci->pp);
You should first check for the existence of the callback before invoking. This
applies to all callbacks in this patch.
> +
> + /*
> + * PCI Express Base Specification Rev 4.0
> + * 5.3.3.2.1 PME Synchronization
> + * Recommand 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);
Is there no way to wait for PME_To_Ack TLP?
> + if (ret) {
> + dev_err(pci->dev, "PCIe link enter L2 timeout! ltssm = 0x%x\n", val);
> + return ret;
> + }
> +
> + dw_pcie_set_dstate(pci, 0x3);
> +
> + 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;
> +
> + dw_pcie_set_dstate(pci, 0x0);
> +
> + pci->pp.ops->exit_from_l2(&pci->pp);
> +
> + /* delay 10 ms to access EP */
Is this delay as part of the DWC spec? If so, please quote the section.
> + mdelay(10);
> +
> + ret = pci->pp.ops->host_init(&pci->pp);
> + if (ret) {
> + dev_err(pci->dev, "ls_pcie_host_init failed! ret = 0x%x\n", ret);
s/ls_pcie_host_init/Host init
> + return ret;
> + }
> +
> + dw_pcie_setup_rc(&pci->pp);
> +
Don't you need to configure iATU?
> + ret = dw_pcie_wait_for_link(pci);
Don't you need to start the link beforehand?
> + if (ret) {
> + dev_err(pci->dev, "wait link up timeout! ret = 0x%x\n", ret);
dw_pcie_wait_for_link() itself prints error message on failure. So no need to do
the same here.
- Mani
> + 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 79713ce075cc..effb07a506e4 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 align PCIE_PORT_DEBUG0 bit0:5 */
> + 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
>
--
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