Re: [PATCH v4 7/7] PCI: dwc: Add validation that PCIe core is set to correct mode

Andrew Murray
2019-08-22T11:13:20Z

On Wed, Aug 21, 2019 at 06:47:45PM +0300, Jonathan Chocron wrote:
> Some PCIe controllers can be set to either Host or EP according to some
> early boot FW. To make sure there is no discrepancy (e.g. FW configured
> the port to EP mode while the DT specifies it as a host bridge or vice
> versa), a check has been added for each mode.
>
> Signed-off-by: Jonathan Chocron <jonnyc@amazon.com>
> Acked-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
> ---
> drivers/pci/controller/dwc/pcie-designware-ep.c | 8 ++++++++
> drivers/pci/controller/dwc/pcie-designware-host.c | 8 ++++++++
> 2 files changed, 16 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index 2bf5a35c0570..00e59a134b93 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -531,6 +531,7 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
> int ret;
> u32 reg;
> void *addr;
> + u8 hdr_type;
> unsigned int nbars;
> unsigned int offset;
> struct pci_epc *epc;
> @@ -543,6 +544,13 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
> return -EINVAL;
> }
>
> + hdr_type = dw_pcie_readb_dbi(pci, PCI_HEADER_TYPE);
> + if (hdr_type != PCI_HEADER_TYPE_NORMAL) {
> + dev_err(pci->dev, "PCIe controller is not set to EP mode (hdr_type:0x%x)!\n",
> + hdr_type);
> + return -EIO;
> + }
> +
> ret = of_property_read_u32(np, "num-ib-windows", &ep->num_ib_windows);
> if (ret < 0) {
> dev_err(dev, "Unable to read *num-ib-windows* property\n");
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index f93252d0da5b..d2ca748e4c85 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -323,6 +323,7 @@ int dw_pcie_host_init(struct pcie_port *pp)
> struct pci_bus *child;
> struct pci_host_bridge *bridge;
> struct resource *cfg_res;
> + u8 hdr_type;
> int ret;
>
> raw_spin_lock_init(&pci->pp.lock);
> @@ -396,6 +397,13 @@ int dw_pcie_host_init(struct pcie_port *pp)
> }
> }
>
> + hdr_type = dw_pcie_readb_dbi(pci, PCI_HEADER_TYPE);

Do we know if it's always safe to read these registers at this point in time?

Later in dw_pcie_host_init we call pp->ops->host_init - looking at the
implementations of .host_init I can see:

- resets being performed (qcom_ep_reset_assert,
artpec6_pcie_assert_core_reset, imx6_pcie_assert_core_reset)
- changes to config space registers (ks_pcie_init_id, dw_pcie_setup_rc)
including setting PCI_CLASS_DEVICE
- and clocks being enabled (qcom_pcie_init_1_0_0)

I'm not sure if your changes would cause anything to break for these other
controllers (or future controllers) as I couldn't see any other reads to the
config.

Given that we are reading config space should dw_pcie_rd_own_conf be used?
(For example kirin_pcie_rd_own_conf does something special).

Thanks,

Andrew Murray

> + if (hdr_type != PCI_HEADER_TYPE_BRIDGE) {
> + dev_err(pci->dev, "PCIe controller is not set to bridge type (hdr_type: 0x%x)!\n",
> + hdr_type);
> + return -EIO;
> + }
> +
> pp->mem_base = pp->mem->start;
>
> if (!pp->va_cfg0_base) {
> --
> 2.17.1
>