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Date:   Mon, 21 Aug 2023 10:21:05 +0200
From:   Lorenzo Pieralisi <lpieralisi@kernel.org>
To:     Frank Li <Frank.li@nxp.com>, manivannan.sadhasivam@linaro.org
Cc:     helgaas@kernel.org, bhelgaas@google.com,
        devicetree@vger.kernel.org, gustavo.pimentel@synopsys.com,
        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 v11 3/3] PCI: layerscape: Add power management support
 for ls1028a
Message-ID: <ZOMecaueyN3cutUH@lpieralisi>
References: <20230809153540.834653-1-Frank.Li@nxp.com>
 <20230809153540.834653-4-Frank.Li@nxp.com>
 <ZNzrgr3a13vm6Yqi@lpieralisi>
 <ZN6iarqhryMHmwLh@lizhi-Precision-Tower-5810>
MIME-Version: 1.0
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Content-Disposition: inline
In-Reply-To: <ZN6iarqhryMHmwLh@lizhi-Precision-Tower-5810>
Precedence: bulk

On Thu, Aug 17, 2023 at 06:42:50PM -0400, Frank Li wrote:
> On Wed, Aug 16, 2023 at 05:30:10PM +0200, Lorenzo Pieralisi wrote:
> > On Wed, Aug 09, 2023 at 11:35:40AM -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 | 130 ++++++++++++++++++--
> > >  1 file changed, 121 insertions(+), 9 deletions(-)
> > > 
> > > diff --git a/drivers/pci/controller/dwc/pci-layerscape.c b/drivers/pci/controller/dwc/pci-layerscape.c
> > > index ed5fb492fe084..b49f654335fd7 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 +90,60 @@ 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;
> > > +
> > > +	val = ls_pcie_pf_readl(pcie, LS_PCIE_PF_MCR);
> > > +	val |= PF_MCR_EXL2S;
> > > +	ls_pcie_pf_writel(pcie, LS_PCIE_PF_MCR, val);
> > 
> > What is this write transaction generating in HW ?
> 
> I don't think send anything to to pci bus because it was called before
> host init.
> 
> The spec of ls1028 is not clear enough.
> 
> `EXL2S: exit l2 state command. when set to 1, an L2 exit command is
> generated. The bit is self clearing. Once the bit is set. SW needs to wait
> for the bit to selfclear before sending a new command'
> 
> > 
> > Why is it needed ? Shouldn't L2 exit happen automatically
> > in HW ?
> 
> I tried remove this, PCI can't resume. I think this is specific for ls1028
> chip to clear internal logic.

Well, if you don't even know what this does how can you write a sane
device driver ?

Can you ask designers a more detailed description please ?

> > > +
> > > +	ret = readx_poll_timeout(ls_pcie_pf_readl_addr, LS_PCIE_PF_MCR,
> > > +				 val, !(val & PF_MCR_EXL2S),
> > > +				 PCIE_PME_TO_L2_TIMEOUT_US/10,
> > > +			PCIE_PME_TO_L2_TIMEOUT_US);
> > 
> > And why is the timeout value the same used for the PME_turn_off message ?
> 
> I think No spec define it, just reused it. use PCIE_PME_TO_L2_TIMEOUT_US
> may cause confuse. What's do you prefered? Just use number,such as 10ms.

This delay value is misleading, it is not good to reuse a value for
a delay that is most certainly controller specific.

From this discussion I would say that having pme_turn_off() and
exit_from_l2() hooks is generalizing something we don't know yet
it is needed for all DWC based controllers.

It is probably worth keeping the layerscape specific changes in
the layerscape driver and from there call the "generic" DWC
suspend/resume functions:

dw_pcie_suspend_noirq()
dw_pcie_resume_noirq()

rather than adding hooks that we barely know what they are needed for.

Mani, what do you think ?

Thanks,
Lorenzo

> 
> > 
> > Thanks,
> > Lorenzo
> > 
> > > +	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 +162,28 @@ 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,
> > > +	.exit_from_l2 = ls_pcie_exit_from_l2,
> > > +};
> > > +
> > > +static const struct ls_pcie_drvdata ls1021a_drvdata = {
> > > +};
> > > +
> > > +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 +202,8 @@ 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 +214,10 @@ 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 +226,37 @@ 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;
> > > +
> > > +	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
> > >