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Message-ID: <20231130164323.GT3043@thinkpad>
Date: Thu, 30 Nov 2023 22:13:23 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Frank Li <Frank.Li@....com>
Cc: bhelgaas@...gle.com, imx@...ts.linux.dev, kw@...ux.com,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-pci@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
lpieralisi@...nel.org, minghuan.Lian@....com, mingkai.hu@....com,
robh@...nel.org, roy.zang@....com
Subject: Re: [PATCH v4 2/4] PCI: layerscape: Add suspend/resume for ls1021a
On Wed, Nov 29, 2023 at 04:44:10PM -0500, Frank Li wrote:
> ls1021a add suspend/resume support.
>
"Add suspend/resume support for Layerscape LS1021a"
> In the suspend path, PME_Turn_Off message is sent to the endpoint to
> transition the link to L2/L3_Ready state. In this SoC, there is no way to
> check if the controller has received the PME_To_Ack from the endpoint or
> not. So to be on the safer side, the driver just waits for
> PCIE_PME_TO_L2_TIMEOUT_US before asserting the SoC specific PMXMTTURNOFF
> bit to complete the PME_Turn_Off handshake. This link would then enter
"Then the link would enter L2/L3 state depending on the VAUX supply."
> L2/L3 state depending on the VAUX supply.
>
> In the resume path, the link is brought back from L2 to L0 by doing a
> software reset.
>
> Signed-off-by: Frank Li <Frank.Li@....com>
Couple of comments below. But the patch is looking good now. Thanks for the
update.
> ---
>
> Notes:
> Change from v3 to v4
> - update commit message.
> - it is reset a glue logic part for PCI controller.
> - use regmap_write_bits() to reduce code change.
>
> Change from v2 to v3
> - update according to mani's feedback
> change from v1 to v2
> - change subject 'a' to 'A'
>
> drivers/pci/controller/dwc/pci-layerscape.c | 83 ++++++++++++++++++++-
> 1 file changed, 82 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/controller/dwc/pci-layerscape.c b/drivers/pci/controller/dwc/pci-layerscape.c
> index aea89926bcc4f..42bca2c3b5c3e 100644
> --- a/drivers/pci/controller/dwc/pci-layerscape.c
> +++ b/drivers/pci/controller/dwc/pci-layerscape.c
> @@ -35,11 +35,19 @@
> #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 {
> const u32 pf_off;
> + const struct dw_pcie_host_ops *ops;
> int (*exit_from_l2)(struct dw_pcie_rp *pp);
> + bool scfg_support;
> bool pm_support;
> };
>
> @@ -47,6 +55,8 @@ 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;
> };
>
> @@ -171,13 +181,65 @@ static int ls_pcie_host_init(struct dw_pcie_rp *pp)
> return 0;
> }
>
> +static void scfg_pcie_send_turnoff_msg(struct regmap *scfg, u32 reg, u32 mask)
> +{
> + /* Send PME_Turn_Off message */
> + regmap_write_bits(scfg, reg, mask, mask);
> +
> + /*
> + * 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);
> +
> + /*
> + * Layerscape hardware reference manual recommends clearing the PMXMTTURNOFF bit
> + * to complete the PME_Turn_Off handshake.
> + */
> + regmap_write_bits(scfg, reg, mask, 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);
> +
> + scfg_pcie_send_turnoff_msg(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), PMXMTTURNOFF);
> +}
> +
> +static int scfg_pcie_exit_from_l2(struct regmap *scfg, u32 reg, u32 mask)
> +{
> + /* Only way exit from l2 is that do software reset */
"Only way exit from L2 is by doing a software reset of the controller"
I really hope that the reset is not a global controller reset i.e., not
resetting all CSRs.
> + regmap_write_bits(scfg, reg, mask, mask);
> +
No need of a newline.
> + regmap_write_bits(scfg, reg, mask, 0);
> +
> + return 0;
> +}
> +
> +static int 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);
> +
> + return scfg_pcie_exit_from_l2(pcie->scfg, SCFG_PEXSFTRSTCR, PEXSR(pcie->index));
> +}
> +
> 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 = ls_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,
> + .scfg_support = true,
> + .ops = &ls1021a_pcie_host_ops,
> + .exit_from_l2 = ls1021a_pcie_exit_from_l2,
> };
>
> static const struct ls_pcie_drvdata layerscape_drvdata = {
> @@ -205,6 +267,8 @@ static int ls_pcie_probe(struct platform_device *pdev)
> struct dw_pcie *pci;
> struct ls_pcie *pcie;
> struct resource *dbi_base;
> + u32 index[2];
> + int ret;
>
> pcie = devm_kzalloc(dev, sizeof(*pcie), GFP_KERNEL);
> if (!pcie)
> @@ -220,6 +284,7 @@ static int ls_pcie_probe(struct platform_device *pdev)
> pci->pp.ops = &ls_pcie_host_ops;
>
> pcie->pci = pci;
> + pci->pp.ops = pcie->drvdata->ops ? pcie->drvdata->ops : &ls_pcie_host_ops;
pp.ops is already assigned to &ls_pcie_host_ops above. But I think for
consistency, you should pass ls_pcie_host_ops to the "ops" member of
layerscape_drvdata and just use:
pci->pp.ops = pcie->drvdata->ops;
It looks a lot cleaner.
>
> dbi_base = platform_get_resource_byname(pdev, IORESOURCE_MEM, "regs");
> pci->dbi_base = devm_pci_remap_cfg_resource(dev, dbi_base);
> @@ -230,6 +295,22 @@ static int ls_pcie_probe(struct platform_device *pdev)
>
> pcie->pf_base = pci->dbi_base + pcie->drvdata->pf_off;
>
> + if (pcie->drvdata->scfg_support) {
> + pcie->scfg = syscon_regmap_lookup_by_phandle(dev->of_node, "fsl,pcie-scfg");
> + if (IS_ERR(pcie->scfg)) {
> + dev_err(dev, "No syscfg phandle specified\n");
> + return PTR_ERR(pcie->scfg);
> + }
> +
> + ret = of_property_read_u32_array(dev->of_node, "fsl,pcie-scfg", index, 2);
> + if (ret) {
> + pcie->scfg = NULL;
No need to set it to NULL in the case of probe failure.
- Mani
--
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