On Tue, Feb 25, 2025 at 05:15:07PM +0530, Krishna Chaitanya Chundru wrote:
> PCIe equalization presets are predefined settings used to optimize
> signal integrity by compensating for signal loss and distortion in
> high-speed data transmission.
>
> Based upon the number of lanes and the data rate supported, write
> the preset data read from the device tree in to the lane equalization
> control registers.
>
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@xxxxxxxxxxxxxxxx>
> ---
> drivers/pci/controller/dwc/pcie-designware-host.c | 66 +++++++++++++++++++++++
> drivers/pci/controller/dwc/pcie-designware.h | 3 ++
> include/uapi/linux/pci_regs.h | 3 ++
> 3 files changed, 72 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index dd56cc02f4ef..ea596119de92 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -507,6 +507,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
> if (pci->num_lanes < 1)
> pci->num_lanes = dw_pcie_link_get_max_link_width(pci);
>
> + ret = of_pci_get_equalization_presets(dev, &pp->presets, pci->num_lanes);
> + if (ret)
> + goto err_free_msi;
> +
> /*
> * Allocate the resource for MSG TLP before programming the iATU
> * outbound window in dw_pcie_setup_rc(). Since the allocation depends
> @@ -808,6 +812,67 @@ static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)
> return 0;
> }
>
> +static void dw_pcie_program_presets(struct dw_pcie_rp *pp, enum pci_bus_speed speed)
> +{
> + struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> + u8 lane_eq_offset, lane_reg_size, cap_id;
> + u8 *presets;
> + u32 cap;
> + int i;
> +
> + if (speed == PCIE_SPEED_8_0GT) {
> + presets = (u8 *)pp->presets.eq_presets_8gts;
> + lane_eq_offset = PCI_SECPCI_LE_CTRL;
> + cap_id = PCI_EXT_CAP_ID_SECPCI;
> + /* For data rate of 8 GT/S each lane equalization control is 16bits wide*/
> + lane_reg_size = 0x2;
> + } else if (speed == PCIE_SPEED_16_0GT) {
> + presets = pp->presets.eq_presets_Ngts[EQ_PRESET_TYPE_16GTS];
> + lane_eq_offset = PCI_PL_16GT_LE_CTRL;
> + cap_id = PCI_EXT_CAP_ID_PL_16GT;
> + lane_reg_size = 0x1;
> + } else {
> + dev_WARN_ONCE(pci->dev, 1, "Not supported data rate %s\n",
> + pci_speed_string(speed));
No, this is not what I asked for. You should warn only when there is atleast one
of the preset properties are specified in DT. But I think that would complicate
the code. So let's just trust DT here and add the warning later if needed.
> + return;
> + }
> +
> + if (presets[0] == PCI_EQ_RESV) {
> + dev_WARN_ONCE(pci->dev, 1,
> + "Lane equalization preset properties are missing for %s\n",
> + pci_speed_string(speed));
Same here. This is going to trigger warning on all DWC platforms. Please remove
it.
- Mani
--
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