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Date: Fri, 31 May 2024 12:14:18 -0400
From: Frank Li <Frank.li@nxp.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Richard Zhu <hongxing.zhu@nxp.com>,
	Lucas Stach <l.stach@pengutronix.de>,
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	Jason Gunthorpe <jgg@ziepe.ca>,
	Alyssa Rosenzweig <alyssa@rosenzweig.io>,
	Marc Zyngier <maz@kernel.org>
Subject: Re: [PATCH v5 08/12] PCI: imx6: Config look up table(LUT) to support
 MSI ITS and IOMMU for i.MX95
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References: <20240528-pci2_upstream-v5-8-750aa7edb8e2@nxp.com>
 <20240530230832.GA474962@bhelgaas>
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On Thu, May 30, 2024 at 06:08:32PM -0500, Bjorn Helgaas wrote:
> [+cc IOMMU and pcie-apple.c folks for comment]
> 
> On Tue, May 28, 2024 at 03:39:21PM -0400, Frank Li wrote:
> > For the i.MX95, configuration of a LUT is necessary to convert Bus Device
> > Function (BDF) to stream IDs, which are utilized by both IOMMU and ITS.
> > This involves examining the msi-map and smmu-map to ensure consistent
> > mapping of PCI BDF to the same stream IDs. Subsequently, LUT-related
> > registers are configured. In the absence of an msi-map, the built-in MSI
> > controller is utilized as a fallback.
> > 
> > Additionally, register a PCI bus notifier to trigger imx_pcie_add_device()
> > upon the appearance of a new PCI device and when the bus is an iMX6 PCI
> > controller. This function configures the correct LUT based on Device Tree
> > Settings (DTS).
> 
> This scheme is pretty similar to apple_pcie_bus_notifier().  If we
> have to do this, I wish it were *more* similar, i.e., copy the
> function names, bitmap tracking, code structure, etc.

Actually, I refer apple_pcie_bus_notifier(). I can't direct use apple's
implement because in imx95 have difference PCI host controller, another one
is PCI ECAM netc controller. At lease function name should be similar with
apple. 

> 
> I don't really know how stream IDs work, but I assume they are used on
> most or all arm64 platforms, so I'm a little surprised that of all the
> PCI host drivers used on arm64, only pcie-apple.c and pci-imx6.c need
> this notifier.  
> 
> There's this path, which is pretty generic and does at least the
> of_map_id() part of what you're doing in imx_pcie_add_device():
> 
>     __driver_probe_device
>       really_probe
>         pci_dma_configure                       # pci_bus_type.dma_configure
>           of_dma_configure
>             of_dma_configure_id
>               of_iommu_configure
>                 of_pci_iommu_init
>                   of_iommu_configure_dev_id
>                     of_map_id
>                     of_iommu_xlate
>                       ops = iommu_ops_from_fwnode
>                       iommu_fwspec_init
>                       ops->of_xlate(dev, iommu_spec)
> 
> Maybe this needs to be extended somehow with a hook to do the
> device-specific work like updating the LUT?  Just speculating here,
> the IOMMU folks will know how this is expected to work.

Let me do more study. But I think ITS also need stream ID, not sure if
only hook IOMMU can work. Some configuration, IOMMU have not enabled. but
ITS need it.

Ideally, pci system can provide a hook function to host bridge when new
device add and remove.

Frank

> 
> Some typos and minor comments below.
> 
> > Signed-off-by: Frank Li <Frank.Li@nxp.com>
> > ---
> >  drivers/pci/controller/dwc/pci-imx6.c | 175 +++++++++++++++++++++++++++++++++-
> >  1 file changed, 174 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> > index 29309ad0e352b..8ecc00049e20b 100644
> > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > @@ -54,6 +54,22 @@
> >  #define IMX95_PE0_GEN_CTRL_3			0x1058
> >  #define IMX95_PCIE_LTSSM_EN			BIT(0)
> >  
> > +#define IMX95_PE0_LUT_ACSCTRL			0x1008
> > +#define IMX95_PEO_LUT_RWA			BIT(16)
> > +#define IMX95_PE0_LUT_ENLOC			GENMASK(4, 0)
> > +
> > +#define IMX95_PE0_LUT_DATA1			0x100c
> > +#define IMX95_PE0_LUT_VLD			BIT(31)
> > +#define IMX95_PE0_LUT_DAC_ID			GENMASK(10, 8)
> > +#define IMX95_PE0_LUT_STREAM_ID			GENMASK(5, 0)
> > +
> > +#define IMX95_PE0_LUT_DATA2			0x1010
> > +#define IMX95_PE0_LUT_REQID			GENMASK(31, 16)
> > +#define IMX95_PE0_LUT_MASK			GENMASK(15, 0)
> > +
> > +#define IMX95_SID_MASK				GENMASK(5, 0)
> > +#define IMX95_MAX_LUT				32
> > +
> >  #define to_imx_pcie(x)	dev_get_drvdata((x)->dev)
> >  
> >  enum imx_pcie_variants {
> > @@ -79,6 +95,7 @@ enum imx_pcie_variants {
> >  #define IMX_PCIE_FLAG_HAS_PHY_RESET		BIT(5)
> >  #define IMX_PCIE_FLAG_HAS_SERDES		BIT(6)
> >  #define IMX_PCIE_FLAG_SUPPORT_64BIT		BIT(7)
> > +#define IMX_PCIE_FLAG_MONITOR_DEV		BIT(8)
> >  
> >  #define imx_check_flag(pci, val)     (pci->drvdata->flags & val)
> >  
> > @@ -132,6 +149,8 @@ struct imx_pcie {
> >  	struct device		*pd_pcie_phy;
> >  	struct phy		*phy;
> >  	const struct imx_pcie_drvdata *drvdata;
> > +
> > +	struct mutex		lock;
> >  };
> >  
> >  /* Parameters for the waiting for PCIe PHY PLL to lock on i.MX7 */
> > @@ -215,6 +234,66 @@ static int imx95_pcie_init_phy(struct imx_pcie *imx_pcie)
> >  	return 0;
> >  }
> >  
> > +static int imx_pcie_config_lut(struct imx_pcie *imx_pcie, u16 reqid, u8 sid)
> > +{
> > +	struct dw_pcie *pci = imx_pcie->pci;
> > +	struct device *dev = pci->dev;
> > +	u32 data1, data2;
> > +	int i;
> > +
> > +	if (sid >= 64) {
> > +		dev_err(dev, "Invalid SID for index %d\n", sid);
> > +		return -EINVAL;
> > +	}
> > +
> > +	guard(mutex)(&imx_pcie->lock);
> > +
> > +	for (i = 0; i < IMX95_MAX_LUT; i++) {
> > +		regmap_write(imx_pcie->iomuxc_gpr, IMX95_PE0_LUT_ACSCTRL, IMX95_PEO_LUT_RWA | i);
> > +
> > +		regmap_read(imx_pcie->iomuxc_gpr, IMX95_PE0_LUT_DATA1, &data1);
> > +		if (data1 & IMX95_PE0_LUT_VLD)
> > +			continue;
> > +
> > +		data1 = FIELD_PREP(IMX95_PE0_LUT_DAC_ID, 0);
> > +		data1 |= FIELD_PREP(IMX95_PE0_LUT_STREAM_ID, sid);
> > +		data1 |= IMX95_PE0_LUT_VLD;
> > +
> > +		regmap_write(imx_pcie->iomuxc_gpr, IMX95_PE0_LUT_DATA1, data1);
> > +
> > +		data2 = 0xffff;
> > +		data2 |= FIELD_PREP(IMX95_PE0_LUT_REQID, reqid);
> > +
> > +		regmap_write(imx_pcie->iomuxc_gpr, IMX95_PE0_LUT_DATA2, data2);
> > +
> > +		regmap_write(imx_pcie->iomuxc_gpr, IMX95_PE0_LUT_ACSCTRL, i);
> > +
> > +		return 0;
> > +	}
> > +
> > +	dev_err(dev, "All lut already used\n");
> > +	return -EINVAL;
> > +}
> > +
> > +static void imx_pcie_remove_lut(struct imx_pcie *imx_pcie, u16 reqid)
> > +{
> > +	u32 data2 = 0;
> > +	int i;
> > +
> > +	guard(mutex)(&imx_pcie->lock);
> > +
> > +	for (i = 0; i < IMX95_MAX_LUT; i++) {
> > +		regmap_write(imx_pcie->iomuxc_gpr, IMX95_PE0_LUT_ACSCTRL, IMX95_PEO_LUT_RWA | i);
> > +
> > +		regmap_read(imx_pcie->iomuxc_gpr, IMX95_PE0_LUT_DATA2, &data2);
> > +		if (FIELD_GET(IMX95_PE0_LUT_REQID, data2) == reqid) {
> > +			regmap_write(imx_pcie->iomuxc_gpr, IMX95_PE0_LUT_DATA1, 0);
> > +			regmap_write(imx_pcie->iomuxc_gpr, IMX95_PE0_LUT_DATA2, 0);
> > +			regmap_write(imx_pcie->iomuxc_gpr, IMX95_PE0_LUT_ACSCTRL, i);
> > +		}
> > +	}
> > +}
> > +
> >  static void imx_pcie_configure_type(struct imx_pcie *imx_pcie)
> >  {
> >  	const struct imx_pcie_drvdata *drvdata = imx_pcie->drvdata;
> > @@ -1232,6 +1311,85 @@ static int imx_pcie_resume_noirq(struct device *dev)
> >  	return 0;
> >  }
> >  
> > +static bool imx_pcie_match_device(struct pci_bus *bus);
> 
> Can you add the imx_pcie_match_device() earlier in the file so we
> don't need this forward declaration?

imx_pcie_match_device() use global veriable imx_pcie_driver, which close to
end of the file. There will be bigger change if move imx_pcie_driver ahead.

> 
> > +static int imx_pcie_add_device(struct imx_pcie *imx_pcie, struct pci_dev *pdev)
> > +{
> > +	u32 sid_i = 0, sid_m = 0, rid = pci_dev_id(pdev);
> > +	struct device *dev = imx_pcie->pci->dev;
> > +	int err;
> > +
> > +	err = of_map_id(dev->of_node, rid, "iommu-map", "iommu-map-mask", NULL, &sid_i);
> > +	if (err)
> > +		return err;
> > +
> > +	err = of_map_id(dev->of_node, rid, "msi-map", "msi-map-mask", NULL, &sid_m);
> > +	if (err)
> > +		return err;
> > +
> > +	if (sid_i != rid && sid_m != rid)
> > +		if ((sid_i & IMX95_SID_MASK) != (sid_m & IMX95_SID_MASK)) {
> > +			dev_err(dev, "its and iommu stream id miss match, please check dts file\n");
> > +			return -EINVAL;
> > +		}
> > +
> > +	/* if iommu-map is not existed then use msi-map's stream id*/
> 
> Capitalize consistently, e.g., the most comments in this file start
> with a capital letter.
> 
> s/is not existed/does not exist/
> 
> Add space before closing */
> 
> > +	if (sid_i == rid)
> > +		sid_i = sid_m;
> > +
> > +	sid_i &= IMX95_SID_MASK;
> > +
> > +	if (sid_i != rid)
> > +		return imx_pcie_config_lut(imx_pcie, rid, sid_i);
> > +
> > +	/* Use dwc built-in MSI controller */
> > +	return 0;
> > +}
> > +
> > +static void imx_pcie_del_device(struct imx_pcie *imx_pcie, struct pci_dev *pdev)
> > +{
> > +	imx_pcie_remove_lut(imx_pcie, pci_dev_id(pdev));
> > +}
> > +
> > +
> > +static int imx_pcie_bus_notifier(struct notifier_block *nb, unsigned long action, void *data)
> > +{
> > +	struct pci_host_bridge *host;
> > +	struct imx_pcie *imx_pcie;
> > +	struct pci_dev *pdev;
> > +	int err;
> > +
> > +	pdev = to_pci_dev(data);
> > +	host = pci_find_host_bridge(pdev->bus);
> > +
> > +	if (!imx_pcie_match_device(host->bus))
> > +		return NOTIFY_OK;
> > +
> > +	imx_pcie = to_imx_pcie(to_dw_pcie_from_pp(host->sysdata));
> > +
> > +	if (!imx_check_flag(imx_pcie, IMX_PCIE_FLAG_MONITOR_DEV))
> > +		return NOTIFY_OK;
> > +
> > +	switch (action) {
> > +	case BUS_NOTIFY_ADD_DEVICE:
> > +		err = imx_pcie_add_device(imx_pcie, pdev);
> > +		if (err)
> > +			return notifier_from_errno(err);
> > +		break;
> > +	case BUS_NOTIFY_DEL_DEVICE:
> > +		imx_pcie_del_device(imx_pcie, pdev);
> > +		break;
> > +	default:
> > +		return NOTIFY_DONE;
> > +	}
> > +
> > +	return NOTIFY_OK;
> > +}
> > +
> > +static struct notifier_block imx_pcie_nb = {
> > +	.notifier_call = imx_pcie_bus_notifier,
> > +};
> > +
> >  static const struct dev_pm_ops imx_pcie_pm_ops = {
> >  	NOIRQ_SYSTEM_SLEEP_PM_OPS(imx_pcie_suspend_noirq,
> >  				  imx_pcie_resume_noirq)
> > @@ -1264,6 +1422,8 @@ static int imx_pcie_probe(struct platform_device *pdev)
> >  	imx_pcie->pci = pci;
> >  	imx_pcie->drvdata = of_device_get_match_data(dev);
> >  
> > +	mutex_init(&imx_pcie->lock);
> > +
> >  	/* Find the PHY if one is defined, only imx7d uses it */
> >  	np = of_parse_phandle(node, "fsl,imx7d-pcie-phy", 0);
> >  	if (np) {
> > @@ -1551,7 +1711,8 @@ static const struct imx_pcie_drvdata drvdata[] = {
> >  	},
> >  	[IMX95] = {
> >  		.variant = IMX95,
> > -		.flags = IMX_PCIE_FLAG_HAS_SERDES,
> > +		.flags = IMX_PCIE_FLAG_HAS_SERDES |
> > +			 IMX_PCIE_FLAG_MONITOR_DEV,
> >  		.clk_names = imx8mq_clks,
> >  		.clks_cnt = ARRAY_SIZE(imx8mq_clks),
> >  		.ltssm_off = IMX95_PE0_GEN_CTRL_3,
> > @@ -1687,6 +1848,8 @@ DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_VENDOR_ID_SYNOPSYS, 0xabcd,
> >  
> >  static int __init imx_pcie_init(void)
> >  {
> > +	int ret;
> > +
> >  #ifdef CONFIG_ARM
> >  	struct device_node *np;
> >  
> > @@ -1705,7 +1868,17 @@ static int __init imx_pcie_init(void)
> >  	hook_fault_code(8, imx6q_pcie_abort_handler, SIGBUS, 0,
> >  			"external abort on non-linefetch");
> >  #endif
> > +	ret = bus_register_notifier(&pci_bus_type, &imx_pcie_nb);
> > +	if (ret)
> > +		return ret;
> 
> I think this should go in imx6_pcie_probe().

The same nb only register once. If move to probe, bus_register_notifier()
will return error and dump error message when second pci controller
instance probe.

> 
> >  	return platform_driver_register(&imx_pcie_driver);
> >  }
> > +
> > +static void __exit imx_pcie_exit(void)
> > +{
> > +	bus_unregister_notifier(&pci_bus_type, &imx_pcie_nb);
> 
> It looks like this driver is removable?

Actually, I think not. I am not sure how to prevent driver remove. There
are raise condition when driver remove and a pci device hot plug at the
same time although hot plug pci have not implement yet in imx platform.

> 
> What happens when an external abort occurs after the
> imx6q_pcie_abort_handler() text is removed?
> 
> > +}
> > +
> >  device_initcall(imx_pcie_init);
> > +__exitcall(imx_pcie_exit);
> > 
> > -- 
> > 2.34.1
> >