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Message-ID: <ZUPmqAa6B4nU/F9V@lizhi-Precision-Tower-5810>
Date: Thu, 2 Nov 2023 14:14:46 -0400
From: Frank Li <Frank.li@....com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
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 v3 2/4] PCI: layerscape: Add suspend/resume for ls1021a
On Thu, Nov 02, 2023 at 10:58:09PM +0530, Manivannan Sadhasivam wrote:
> On Tue, Oct 17, 2023 at 03:31:43PM -0400, Frank Li wrote:
> > ls1021a add suspend/resume support.
> >
> > Implement callback ls1021a_pcie_send_turnoff_msg(), which write scfg's
> > SCFG_PEXPMWRCR to issue PME_Turn_off message.
> >
> > Implement ls1021a_pcie_exit_from_l2() to let controller exit L2 state.
> >
>
> I'd like to reword it to better reflect what the patch does:
>
> "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 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."
>
> Although I do have questions on the resume behavior below.
>
> > Signed-off-by: Frank Li <Frank.Li@....com>
> > ---
> >
> > Notes:
> > 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 | 86 ++++++++++++++++++++-
> > 1 file changed, 85 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/controller/dwc/pci-layerscape.c b/drivers/pci/controller/dwc/pci-layerscape.c
> > index aea89926bcc4f..6f47cfe146c44 100644
> > --- a/drivers/pci/controller/dwc/pci-layerscape.c
> > +++ b/drivers/pci/controller/dwc/pci-layerscape.c
> > @@ -35,11 +35,21 @@
> > #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
> >
> > +#define LS_PCIE_DRV_SCFG BIT(0)
> > +
> > struct ls_pcie_drvdata {
> > const u32 pf_off;
> > + const struct dw_pcie_host_ops *ops;
> > int (*exit_from_l2)(struct dw_pcie_rp *pp);
> > + int flags;
>
> Why not "bool scfg_support"?
It will be easy to add new flag if need in future.
>
> > bool pm_support;
> > };
> >
> > @@ -47,6 +57,8 @@ 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 +183,65 @@ 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;
> > +
> > + /* 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 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_read(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), &val);
> > + val &= ~PMXMTTURNOFF;
> > + regmap_write(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), val);
> > +}
> > +
> > +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);
> > + u32 val;
> > +
> > + /* Only way exit from l2 is that do software reset */
>
> So, what does exactly "software reset" mean? Are you resetting the endpoint or
> some specific registers/blocks in the controlleri?
No, it is PCIe controller reset. Not touch endpoint.
>
> Also, what if the link goes to L3 in the case of no VAUX?
I am not exactly sure. it should be related with board design. I supposed
not big difference!
We can improve it when we met it.
>
> > + 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);
> > +
> > + return 0;
> > +}
> > +
> > 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,
> > + .ops = &ls1021a_pcie_host_ops,
> > + .exit_from_l2 = ls1021a_pcie_exit_from_l2,
> > + .flags = LS_PCIE_DRV_SCFG,
> > };
> >
> > static const struct ls_pcie_drvdata layerscape_drvdata = {
> > @@ -205,6 +269,8 @@ 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 +286,7 @@ 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;
> >
> > dbi_base = platform_get_resource_byname(pdev, IORESOURCE_MEM, "regs");
> > pci->dbi_base = devm_pci_remap_cfg_resource(dev, dbi_base);
> > @@ -230,6 +297,23 @@ static int ls_pcie_probe(struct platform_device *pdev)
> >
> > pcie->pf_base = pci->dbi_base + pcie->drvdata->pf_off;
> >
> > + if (pcie->drvdata->flags & LS_PCIE_DRV_SCFG) {
> > +
>
> Remove extra newline.
>
> - Mani
>
> --
> மணிவண்ணன் சதாசிவம்
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