Re: [PATCH v3 2/2] PCI: imx6: Add IOMMU and ITS MSI support for i.MX95

[Marc Zyngier <maz@kernel.org>]

On Sat, 02 Nov 2024 17:26:46 +0000,
Frank Li <Frank.li@nxp.com> wrote:
> 
> On Sat, Nov 02, 2024 at 05:19:37PM +0530, Manivannan Sadhasivam wrote:
> > On Thu, Oct 24, 2024 at 06:34:45PM -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 callback function enable_device() and
> > > disable_device() to config LUT when enable a new PCI device.
> > >
> >
> > Callbacks are not *addition*, but it is how you are implementing the LUT
> > configuration. Please reword it so.
> >
> > > Signed-off-by: Frank Li <Frank.Li@nxp.com>
> > > ---
> > > Change from v2 to v3
> > > - Use the "target" argument of of_map_id()
> > > - Check if rid already in lut table when enable device
> > >
> > > change from v1 to v2
> > > - set callback to pci_host_bridge instead pci->ops.
> > > ---
> > >  drivers/pci/controller/dwc/pci-imx6.c | 159 +++++++++++++++++++++++++++++++++-
> > >  1 file changed, 158 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> > > index 94f3411352bf0..95f06bfb9fc5e 100644
> > > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > > @@ -55,6 +55,22 @@
> > >  #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 {
> > > @@ -82,6 +98,7 @@ 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_HAS_LUT			BIT(8)
> > >
> > >  #define imx_check_flag(pci, val)	(pci->drvdata->flags & val)
> > >
> > > @@ -134,6 +151,7 @@ struct imx_pcie {
> > >  	struct device		*pd_pcie_phy;
> > >  	struct phy		*phy;
> > >  	const struct imx_pcie_drvdata *drvdata;
> > > +	struct mutex		lock;
> >
> > Please add a comment on what the lock is guarding.
> >
> > >  };
> > >
> > >  /* Parameters for the waiting for PCIe PHY PLL to lock on i.MX7 */
> > > @@ -925,6 +943,137 @@ static void imx_pcie_stop_link(struct dw_pcie *pci)
> > >  	imx_pcie_ltssm_disable(dev);
> > >  }
> > >
> > > +static int imx_pcie_add_lut(struct imx_pcie *imx_pcie, u16 reqid, u8 sid)
> >
> > s/reqid/rid
> >
> > > +{
> > > +	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;
> > > +
> > > +		regmap_read(imx_pcie->iomuxc_gpr, IMX95_PE0_LUT_DATA2, &data2);
> > > +
> > > +		/* Needn't add duplicated Request ID */
> > > +		if (reqid == FIELD_GET(IMX95_PE0_LUT_REQID, data2))
> >
> > So this means LUT entry is already present for the given RID (a buggy DT maybe).
> > Don't you need to emit a warning here?
> >
> > > +			return 0;
> > > +	}
> > > +
> >
> > You need to bail out here if no free LUT entry is available. But I'd recommend
> > to combine two loops to avoid having duplicated IMX95_PE0_LUT_VLD checks and
> > program LUT only if there is any free entry available.
> >
> > > +	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 = IMX95_PE0_LUT_MASK;
> >
> > Also add a comment on why the mask is added along with the RID.
> >
> > > +		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");
> >
> > "LUT entry is not available"
> >
> > > +	return -EINVAL;
> > > +}
> > > +
> > > +static void imx_pcie_remove_lut(struct imx_pcie *imx_pcie, u16 reqid)
> >
> > s/reqid/rid
> >
> > > +{
> > > +	u32 data2 = 0;
> >
> > No need to initialize.
> >
> > > +	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);
> > > +
> > > +			break;
> > > +		}
> > > +	}
> > > +}
> > > +
> > > +static int imx_pcie_enable_device(struct pci_host_bridge *bridge, struct pci_dev *pdev)
> > > +{
> > > +	u32 sid_i = 0, sid_m = 0, rid = pci_dev_id(pdev);
> > > +	struct device_node *target;
> > > +	struct imx_pcie *imx_pcie;
> > > +	struct device *dev;
> > > +	int err_i, err_m;
> > > +
> > > +	imx_pcie = to_imx_pcie(to_dw_pcie_from_pp(bridge->sysdata));
> > > +	dev = imx_pcie->pci->dev;
> >
> > You can assign these at initialization time.
> >
> > > +
> > > +	target = NULL;
> > > +	err_i = of_map_id(dev->of_node, rid, "iommu-map", "iommu-map-mask", &target, &sid_i);
> > > +	target = NULL;
> >
> > What is the point in passing 'target' here?
> 
> See https://lore.kernel.org/imx/b479cad6-e0c5-48fb-bb8f-a70f7582cfd5@arm.com/
> Marc Zyngier's comments:

Not quite. That's Robin's email (I never commented on that particular
patch). Nevertheless, "I approve this message".

	M.

-- 
Without deviation from the norm, progress is not possible.