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Date:   Wed, 23 Aug 2023 13:23:05 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
To:     Frank Li <Frank.li@nxp.com>
Cc:     Lorenzo Pieralisi <lpieralisi@kernel.org>, bhelgaas@google.com,
        devicetree@vger.kernel.org, gustavo.pimentel@synopsys.com,
        helgaas@kernel.org, imx@lists.linux.dev, kw@linux.com,
        leoyang.li@nxp.com, linux-arm-kernel@lists.infradead.org,
        linux-imx@nxp.com, linux-kernel@vger.kernel.org,
        linux-pci@vger.kernel.org, lorenzo.pieralisi@arm.com,
        mani@kernel.org, minghuan.lian@nxp.com, mingkai.hu@nxp.com,
        robh+dt@kernel.org, roy.zang@nxp.com, shawnguo@kernel.org,
        zhiqiang.hou@nxp.com
Subject: Re: [PATCH v12 3/3] PCI: layerscape: Add power management support
 for ls1028a
Message-ID: <20230823075305.GG3737@thinkpad>
References: <20230821184815.2167131-1-Frank.Li@nxp.com>
 <20230821184815.2167131-4-Frank.Li@nxp.com>
 <ZOR5k7B3qRFEjPXR@lpieralisi>
 <ZOTGcLa4audY/cTV@lizhi-Precision-Tower-5810>
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In-Reply-To: <ZOTGcLa4audY/cTV@lizhi-Precision-Tower-5810>
Precedence: bulk

On Tue, Aug 22, 2023 at 10:30:08AM -0400, Frank Li wrote:
> On Tue, Aug 22, 2023 at 11:02:11AM +0200, Lorenzo Pieralisi wrote:
> > On Mon, Aug 21, 2023 at 02:48:15PM -0400, Frank Li wrote:
> > > From: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
> > > 
> > > Add PME_Turn_off/PME_TO_Ack handshake sequence for ls1028a platform. Call
> > > common dwc dw_pcie_suspend(resume)_noirq() function when system enter/exit
> > > suspend state.
> > > 
> > > Acked-by: Manivannan Sadhasivam <mani@kernel.org>
> > > Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
> > > Signed-off-by: Frank Li <Frank.Li@nxp.com>
> > > ---
> > >  drivers/pci/controller/dwc/pci-layerscape.c | 135 ++++++++++++++++++--
> > >  1 file changed, 126 insertions(+), 9 deletions(-)
> > > 
> > > diff --git a/drivers/pci/controller/dwc/pci-layerscape.c b/drivers/pci/controller/dwc/pci-layerscape.c
> > > index ed5fb492fe08..97b8d3329df7 100644
> > > --- a/drivers/pci/controller/dwc/pci-layerscape.c
> > > +++ b/drivers/pci/controller/dwc/pci-layerscape.c
> > > @@ -8,9 +8,11 @@
> > >   * Author: Minghuan Lian <Minghuan.Lian@freescale.com>
> > >   */
> > >  
> > > +#include <linux/delay.h>
> > >  #include <linux/kernel.h>
> > >  #include <linux/interrupt.h>
> > >  #include <linux/init.h>
> > > +#include <linux/iopoll.h>
> > >  #include <linux/of_pci.h>
> > >  #include <linux/of_platform.h>
> > >  #include <linux/of_address.h>
> > > @@ -20,6 +22,7 @@
> > >  #include <linux/mfd/syscon.h>
> > >  #include <linux/regmap.h>
> > >  
> > > +#include "../../pci.h"
> > >  #include "pcie-designware.h"
> > >  
> > >  /* PEX Internal Configuration Registers */
> > > @@ -27,12 +30,26 @@
> > >  #define PCIE_ABSERR		0x8d0 /* Bridge Slave Error Response Register */
> > >  #define PCIE_ABSERR_SETTING	0x9401 /* Forward error of non-posted request */
> > >  
> > > +/* PF Message Command Register */
> > > +#define LS_PCIE_PF_MCR		0x2c
> > > +#define PF_MCR_PTOMR		BIT(0)
> > > +#define PF_MCR_EXL2S		BIT(1)
> > > +
> > >  #define PCIE_IATU_NUM		6
> > >  
> > > +struct ls_pcie_drvdata {
> > > +	const u32 pf_off;
> > > +	bool pm_support;
> > > +};
> > > +
> > >  struct ls_pcie {
> > >  	struct dw_pcie *pci;
> > > +	const struct ls_pcie_drvdata *drvdata;
> > > +	void __iomem *pf_base;
> > > +	bool big_endian;
> > >  };
> > >  
> > > +#define ls_pcie_pf_readl_addr(addr)	ls_pcie_pf_readl(pcie, addr)
> > >  #define to_ls_pcie(x)	dev_get_drvdata((x)->dev)
> > >  
> > >  static bool ls_pcie_is_bridge(struct ls_pcie *pcie)
> > > @@ -73,6 +90,64 @@ static void ls_pcie_fix_error_response(struct ls_pcie *pcie)
> > >  	iowrite32(PCIE_ABSERR_SETTING, pci->dbi_base + PCIE_ABSERR);
> > >  }
> > >  
> > > +static u32 ls_pcie_pf_readl(struct ls_pcie *pcie, u32 off)
> > > +{
> > > +	if (pcie->big_endian)
> > > +		return ioread32be(pcie->pf_base + off);
> > > +
> > > +	return ioread32(pcie->pf_base + off);
> > > +}
> > > +
> > > +static void ls_pcie_pf_writel(struct ls_pcie *pcie, u32 off, u32 val)
> > > +{
> > > +	if (pcie->big_endian)
> > > +		iowrite32be(val, pcie->pf_base + off);
> > > +	else
> > > +		iowrite32(val, pcie->pf_base + off);
> > > +}
> > > +
> > > +static void ls_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;
> > > +	int ret;
> > > +
> > > +	val = ls_pcie_pf_readl(pcie, LS_PCIE_PF_MCR);
> > > +	val |= PF_MCR_PTOMR;
> > > +	ls_pcie_pf_writel(pcie, LS_PCIE_PF_MCR, val);
> > > +
> > > +	ret = readx_poll_timeout(ls_pcie_pf_readl_addr, LS_PCIE_PF_MCR,
> > > +				 val, !(val & PF_MCR_PTOMR),
> > > +				 PCIE_PME_TO_L2_TIMEOUT_US/10,
> > > +				 PCIE_PME_TO_L2_TIMEOUT_US);
> > > +	if (ret)
> > > +		dev_err(pcie->pci->dev, "PME_Turn_off timeout\n");
> > > +}
> > > +
> > > +static void ls_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;
> > > +	int ret;
> > > +
> > > +	/*
> > > +	 * Set PF_MCR_EXL2S bit in LS_PCIE_PF_MCR register for the link
> > > +	 * to exit L2 state.
> > > +	 */
> > > +	val = ls_pcie_pf_readl(pcie, LS_PCIE_PF_MCR);
> > > +	val |= PF_MCR_EXL2S;
> > > +	ls_pcie_pf_writel(pcie, LS_PCIE_PF_MCR, val);
> > > +
> > > +	ret = readx_poll_timeout(ls_pcie_pf_readl_addr, LS_PCIE_PF_MCR,
> > > +				 val, !(val & PF_MCR_EXL2S),
> > > +				 1000,
> > > +				 10000);
> > 
> > I can add a comment myself - please explain how this delay was chosen,
> > any piece of information could be useful for a future developer, let
> > me know and I will add it.
> 
> (This value is coming from exited downstream code. It is really hard to
> find original owner and designer to find the reason).
> 
> How about just add below comments?
> 
> "No specific specification defines this timeout value. The timemout of 10ms
> was chosen by the engineer as a sufficient amount of time to allow the
> hardware to complete its actions."
> 

How about, "L1 exit timeout of 10ms is not defined in the spec, but rather
chosen based on the practical observations."

- Mani

> > 
> > > +	if (ret)
> > > +		dev_err(pcie->pci->dev, "L2 exit timeout\n");
> > > +}
> > > +
> > >  static int ls_pcie_host_init(struct dw_pcie_rp *pp)
> > >  {
> > >  	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> > > @@ -91,18 +166,27 @@ static int ls_pcie_host_init(struct dw_pcie_rp *pp)
> > >  
> > >  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 ls_pcie_drvdata ls1021a_drvdata = {
> > 
> > I suggest adding .pm_support = false explicitly here, I can
> > do it myself.
> > 
> > Thanks,
> > Lorenzo
> 
> Thanks!
> 
> > 
> > > +};
> > > +
> > > +static const struct ls_pcie_drvdata layerscape_drvdata = {
> > > +	.pf_off = 0xc0000,
> > > +	.pm_support = true,
> > >  };
> > >  
> > >  static const struct of_device_id ls_pcie_of_match[] = {
> > > -	{ .compatible = "fsl,ls1012a-pcie", },
> > > -	{ .compatible = "fsl,ls1021a-pcie", },
> > > -	{ .compatible = "fsl,ls1028a-pcie", },
> > > -	{ .compatible = "fsl,ls1043a-pcie", },
> > > -	{ .compatible = "fsl,ls1046a-pcie", },
> > > -	{ .compatible = "fsl,ls2080a-pcie", },
> > > -	{ .compatible = "fsl,ls2085a-pcie", },
> > > -	{ .compatible = "fsl,ls2088a-pcie", },
> > > -	{ .compatible = "fsl,ls1088a-pcie", },
> > > +	{ .compatible = "fsl,ls1012a-pcie", .data = &layerscape_drvdata },
> > > +	{ .compatible = "fsl,ls1021a-pcie", .data = &ls1021a_drvdata },
> > > +	{ .compatible = "fsl,ls1028a-pcie", .data = &layerscape_drvdata },
> > > +	{ .compatible = "fsl,ls1043a-pcie", .data = &ls1021a_drvdata },
> > > +	{ .compatible = "fsl,ls1046a-pcie", .data = &layerscape_drvdata },
> > > +	{ .compatible = "fsl,ls2080a-pcie", .data = &layerscape_drvdata },
> > > +	{ .compatible = "fsl,ls2085a-pcie", .data = &layerscape_drvdata },
> > > +	{ .compatible = "fsl,ls2088a-pcie", .data = &layerscape_drvdata },
> > > +	{ .compatible = "fsl,ls1088a-pcie", .data = &layerscape_drvdata },
> > >  	{ },
> > >  };
> > >  
> > > @@ -121,6 +205,8 @@ static int ls_pcie_probe(struct platform_device *pdev)
> > >  	if (!pci)
> > >  		return -ENOMEM;
> > >  
> > > +	pcie->drvdata = of_device_get_match_data(dev);
> > > +
> > >  	pci->dev = dev;
> > >  	pci->pp.ops = &ls_pcie_host_ops;
> > >  
> > > @@ -131,6 +217,10 @@ static int ls_pcie_probe(struct platform_device *pdev)
> > >  	if (IS_ERR(pci->dbi_base))
> > >  		return PTR_ERR(pci->dbi_base);
> > >  
> > > +	pcie->big_endian = of_property_read_bool(dev->of_node, "big-endian");
> > > +
> > > +	pcie->pf_base = pci->dbi_base + pcie->drvdata->pf_off;
> > > +
> > >  	if (!ls_pcie_is_bridge(pcie))
> > >  		return -ENODEV;
> > >  
> > > @@ -139,12 +229,39 @@ static int ls_pcie_probe(struct platform_device *pdev)
> > >  	return dw_pcie_host_init(&pci->pp);
> > >  }
> > >  
> > > +static int ls_pcie_suspend_noirq(struct device *dev)
> > > +{
> > > +	struct ls_pcie *pcie = dev_get_drvdata(dev);
> > > +
> > > +	if (!pcie->drvdata->pm_support)
> > > +		return 0;
> > > +
> > > +	return dw_pcie_suspend_noirq(pcie->pci);
> > > +}
> > > +
> > > +static int ls_pcie_resume_noirq(struct device *dev)
> > > +{
> > > +	struct ls_pcie *pcie = dev_get_drvdata(dev);
> > > +
> > > +	if (!pcie->drvdata->pm_support)
> > > +		return 0;
> > > +
> > > +	ls_pcie_exit_from_l2(&pcie->pci->pp);
> > > +
> > > +	return dw_pcie_resume_noirq(pcie->pci);
> > > +}
> > > +
> > > +static const struct dev_pm_ops ls_pcie_pm_ops = {
> > > +	NOIRQ_SYSTEM_SLEEP_PM_OPS(ls_pcie_suspend_noirq, ls_pcie_resume_noirq)
> > > +};
> > > +
> > >  static struct platform_driver ls_pcie_driver = {
> > >  	.probe = ls_pcie_probe,
> > >  	.driver = {
> > >  		.name = "layerscape-pcie",
> > >  		.of_match_table = ls_pcie_of_match,
> > >  		.suppress_bind_attrs = true,
> > > +		.pm = &ls_pcie_pm_ops,
> > >  	},
> > >  };
> > >  builtin_platform_driver(ls_pcie_driver);
> > > -- 
> > > 2.34.1
> > > 

-- 
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