Re: [PATCH v6 1/2] PCI: dwc: Implement general suspend/resume functionality for L2/L3 transitions

[Manivannan Sadhasivam]

On Mon, Jul 31, 2023 at 03:40:09PM -0400, Frank Li wrote:
> 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.

s/handle/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.
> 
> Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
> ---
> 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@xxxxxxxxx/
> 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@xxxxxxxxxxx>
>   */
>  
> +#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

Rev 4.0 Section 5.3.3.2.1

> +	 * Recommands 1ms to 10ms timeout to check L2 ready

Recommends

Also add a full stop at the end of line.

> +	 */
> +	ret = read_poll_timeout(dw_pcie_get_ltssm, val, val == DW_PCIE_LTSSM_L2_IDLE,
> +				100, 10000, false, pci);

sleep_us value should be 1000 for 1ms.

> +	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);

Why do you want to print "ret" in hex?

How about,

dev_err(pci->dev, "Host init failed: %d\n", ret);

Rest looks good!

- Mani

> +			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
> 

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