Subject: Re: [PATCH 2/3] PCI: layerscape: add suspend/resume for ls1021a

From: Manivannan Sadhasivam <[email-masked]>
Date: Mon, 16 Oct 2023 22:28:24 +0530

On Fri, Sep 15, 2023 at 02:43:05PM -0400, Frank Li wrote:
> ls1021a add suspend/resume support.
> 

Please add what the driver is doing during suspend/resume.

> Signed-off-by: Frank Li <[email-masked]>
> ---
>  drivers/pci/controller/dwc/pci-layerscape.c | 88 ++++++++++++++++++++-
>  1 file changed, 87 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-layerscape.c b/drivers/pci/controller/dwc/pci-layerscape.c
> index 20c48c06e2248..bc5a8ff1a26ce 100644
> --- a/drivers/pci/controller/dwc/pci-layerscape.c
> +++ b/drivers/pci/controller/dwc/pci-layerscape.c
> @@ -35,6 +35,12 @@
>  #define PF_MCR_PTOMR		BIT(0)
>  #define PF_MCR_EXL2S		BIT(1)
>  
> +/* LS1021A PEXn PM Write Control Register */
> +#define SCFG_PEXPMWRCR(idx)	(0x5c + (idx) * 0x64)
> +#define PMXMTTURNOFF		BIT(31)
> +#define SCFG_PEXSFTRSTCR	0x190
> +#define PEXSR(idx)		BIT(idx)
> +
>  #define PCIE_IATU_NUM		6
>  
>  struct ls_pcie_drvdata {
> @@ -48,6 +54,8 @@ struct ls_pcie {
>  	struct dw_pcie *pci;
>  	const struct ls_pcie_drvdata *drvdata;
>  	void __iomem *pf_base;
> +	struct regmap *scfg;
> +	int index;
>  	bool big_endian;
>  };
>  
> @@ -170,13 +178,91 @@ static int ls_pcie_host_init(struct dw_pcie_rp *pp)
>  	return 0;
>  }
>  
> +static void ls1021a_pcie_send_turnoff_msg(struct dw_pcie_rp *pp)
> +{
> +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> +	struct ls_pcie *pcie = to_ls_pcie(pci);
> +	u32 val;
> +
> +	if (!pcie->scfg) {

Can this ever happen?

> +		dev_dbg(pcie->pci->dev, "SYSCFG is NULL\n");
> +		return;
> +	}
> +
> +	/* Send Turn_off message */

"Send PME_Turn_Off message"

> +	regmap_read(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), &val);
> +	val |= PMXMTTURNOFF;
> +	regmap_write(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), val);
> +
> +	/* There are not register to check ACK, so wait PCIE_PME_TO_L2_TIMEOUT_US */

"There is no specific register to check for PME_To_Ack from endpoint. So on the
safe side, wait for PCIE_PME_TO_L2_TIMEOUT_US."

> +	mdelay(PCIE_PME_TO_L2_TIMEOUT_US/1000);
> +
> +	/* Clear Turn_off message */

"PME_Turn_off". But I'm not sure if this is really required. Are you doing it
because the layerspace hw implements the PME_Turn_Off bit as "level triggered"?

> +	regmap_read(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), &val);
> +	val &= ~PMXMTTURNOFF;
> +	regmap_write(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), val);
> +}
> +
> +static void ls1021a_pcie_exit_from_l2(struct dw_pcie_rp *pp)
> +{
> +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> +	struct ls_pcie *pcie = to_ls_pcie(pci);
> +	u32 val;
> +

A comment here would be good.

> +	regmap_read(pcie->scfg, SCFG_PEXSFTRSTCR, &val);
> +	val |= PEXSR(pcie->index);
> +	regmap_write(pcie->scfg, SCFG_PEXSFTRSTCR, val);
> +
> +	regmap_read(pcie->scfg, SCFG_PEXSFTRSTCR, &val);
> +	val &= ~PEXSR(pcie->index);
> +	regmap_write(pcie->scfg, SCFG_PEXSFTRSTCR, val);
> +}
> +
> +static int ls1021a_pcie_host_init(struct dw_pcie_rp *pp)
> +{
> +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> +	struct ls_pcie *pcie = to_ls_pcie(pci);
> +	struct device *dev = pcie->pci->dev;
> +	u32 index[2];
> +	int ret;
> +
> +	ret = ls_pcie_host_init(pp);
> +	if (ret)
> +		return ret;
> +
> +	pcie->scfg = syscon_regmap_lookup_by_phandle(dev->of_node, "fsl,pcie-scfg");
> +	if (IS_ERR(pcie->scfg)) {
> +		ret = PTR_ERR(pcie->scfg);
> +		dev_err(dev, "No syscfg phandle specified\n");
> +		pcie->scfg = NULL;
> +		return ret;
> +	}
> +
> +	ret = of_property_read_u32_array(dev->of_node, "fsl,pcie-scfg", index, 2);
> +	if (ret) {
> +		pcie->scfg = NULL;
> +		return ret;
> +	}
> +
> +	pcie->index = index[1];
> +

The above syscon parsing could be done conditionally during probe itself. There
is no need to do it during host_init() time.

- Mani

> +	return ret;
> +}
> +
>  static const struct dw_pcie_host_ops ls_pcie_host_ops = {
>  	.host_init = ls_pcie_host_init,
>  	.pme_turn_off = ls_pcie_send_turnoff_msg,
>  };
>  
> +static const struct dw_pcie_host_ops ls1021a_pcie_host_ops = {
> +	.host_init = ls1021a_pcie_host_init,
> +	.pme_turn_off = ls1021a_pcie_send_turnoff_msg,
> +};
> +
>  static const struct ls_pcie_drvdata ls1021a_drvdata = {
> -	.pm_support = false,
> +	.pm_support = true,
> +	.ops = &ls1021a_pcie_host_ops,
> +	.exit_from_l2 = ls1021a_pcie_exit_from_l2,
>  };
>  
>  static const struct ls_pcie_drvdata layerscape_drvdata = {
> -- 
> 2.34.1
> 

-- 
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