Re: [PATCH v4 3/3] PCI: qcom: Add RX margining settings for 16 GT/s
From: Manivannan Sadhasivam
Date: Thu May 30 2024 - 10:32:37 EST
On Wed, May 01, 2024 at 09:35:34AM -0700, Shashank Babu Chinta Venkata wrote:
> Add RX lane margining settings for 16 GT/s(GEN 4) data rate. These
> settings improve link stability while operating at high date rates
> and helps to improve signal quality.
>
> Signed-off-by: Shashank Babu Chinta Venkata <quic_schintav@xxxxxxxxxxx>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
- Mani
> ---
> drivers/pci/controller/dwc/pcie-designware.h | 18 +++++++++++
> drivers/pci/controller/dwc/pcie-qcom-common.c | 31 +++++++++++++++++++
> drivers/pci/controller/dwc/pcie-qcom-common.h | 1 +
> drivers/pci/controller/dwc/pcie-qcom-ep.c | 4 ++-
> drivers/pci/controller/dwc/pcie-qcom.c | 4 ++-
> 5 files changed, 56 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index ed0045043847..343450c04e05 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -203,6 +203,24 @@
>
> #define PCIE_PL_CHK_REG_ERR_ADDR 0xB28
>
> +/*
> + * 16 GT/s (GEN4) lane margining register definitions
> + */
> +#define GEN4_LANE_MARGINING_1_OFF 0xb80
> +#define MARGINING_MAX_VOLTAGE_OFFSET GENMASK(29, 24)
> +#define MARGINING_NUM_VOLTAGE_STEPS GENMASK(22, 16)
> +#define MARGINING_MAX_TIMING_OFFSET GENMASK(13, 8)
> +#define MARGINING_NUM_TIMING_STEPS GENMASK(5, 0)
> +
> +#define GEN4_LANE_MARGINING_2_OFF 0xb84
> +#define MARGINING_IND_ERROR_SAMPLER BIT(28)
> +#define MARGINING_SAMPLE_REPORTING_METHOD BIT(27)
> +#define MARGINING_IND_LEFT_RIGHT_TIMING BIT(26)
> +#define MARGINING_IND_UP_DOWN_VOLTAGE BIT(25)
> +#define MARGINING_VOLTAGE_SUPPORTED BIT(24)
> +#define MARGINING_MAXLANES GENMASK(20, 16)
> +#define MARGINING_SAMPLE_RATE_TIMING GENMASK(13, 8)
> +#define MARGINING_SAMPLE_RATE_VOLTAGE GENMASK(5, 0)
> /*
> * iATU Unroll-specific register definitions
> * From 4.80 core version the address translation will be made by unroll
> diff --git a/drivers/pci/controller/dwc/pcie-qcom-common.c b/drivers/pci/controller/dwc/pcie-qcom-common.c
> index 16c277b2e9d4..fe6f7dde5d8c 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom-common.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom-common.c
> @@ -53,6 +53,37 @@ void qcom_pcie_common_set_16gt_eq_settings(struct dw_pcie *pci)
> }
> EXPORT_SYMBOL_GPL(qcom_pcie_common_set_16gt_eq_settings);
>
> +void qcom_pcie_common_set_16gt_rx_margining_settings(struct dw_pcie *pci)
> +{
> + u32 reg;
> +
> + reg = dw_pcie_readl_dbi(pci, GEN4_LANE_MARGINING_1_OFF);
> + reg &= ~(MARGINING_MAX_VOLTAGE_OFFSET |
> + MARGINING_NUM_VOLTAGE_STEPS |
> + MARGINING_MAX_TIMING_OFFSET |
> + MARGINING_NUM_TIMING_STEPS);
> + reg |= FIELD_PREP(MARGINING_MAX_VOLTAGE_OFFSET, 0x24) |
> + FIELD_PREP(MARGINING_NUM_VOLTAGE_STEPS, 0x78) |
> + FIELD_PREP(MARGINING_MAX_TIMING_OFFSET, 0x32) |
> + FIELD_PREP(MARGINING_NUM_TIMING_STEPS, 0x10);
> + dw_pcie_writel_dbi(pci, GEN4_LANE_MARGINING_1_OFF, reg);
> +
> + reg = dw_pcie_readl_dbi(pci, GEN4_LANE_MARGINING_2_OFF);
> + reg |= MARGINING_IND_ERROR_SAMPLER |
> + MARGINING_SAMPLE_REPORTING_METHOD |
> + MARGINING_IND_LEFT_RIGHT_TIMING |
> + MARGINING_VOLTAGE_SUPPORTED;
> + reg &= ~(MARGINING_IND_UP_DOWN_VOLTAGE |
> + MARGINING_MAXLANES |
> + MARGINING_SAMPLE_RATE_TIMING |
> + MARGINING_SAMPLE_RATE_VOLTAGE);
> + reg |= FIELD_PREP(MARGINING_MAXLANES, pci->num_lanes) |
> + FIELD_PREP(MARGINING_SAMPLE_RATE_TIMING, 0x3f) |
> + FIELD_PREP(MARGINING_SAMPLE_RATE_VOLTAGE, 0x3f);
> + dw_pcie_writel_dbi(pci, GEN4_LANE_MARGINING_2_OFF, reg);
> +}
> +EXPORT_SYMBOL_GPL(qcom_pcie_common_set_16gt_rx_margining_settings);
> +
> struct icc_path *qcom_pcie_common_icc_get_resource(struct dw_pcie *pci, const char *path)
> {
> struct icc_path *icc_mem_p;
> diff --git a/drivers/pci/controller/dwc/pcie-qcom-common.h b/drivers/pci/controller/dwc/pcie-qcom-common.h
> index 5c01f6c18b3b..c7eb87aa0677 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom-common.h
> +++ b/drivers/pci/controller/dwc/pcie-qcom-common.h
> @@ -11,3 +11,4 @@ struct icc_path *qcom_pcie_common_icc_get_resource(struct dw_pcie *pci, const ch
> int qcom_pcie_common_icc_init(struct dw_pcie *pci, struct icc_path *icc_mem);
> void qcom_pcie_common_icc_update(struct dw_pcie *pci, struct icc_path *icc_mem);
> void qcom_pcie_common_set_16gt_eq_settings(struct dw_pcie *pci);
> +void qcom_pcie_common_set_16gt_rx_margining_settings(struct dw_pcie *pci);
> diff --git a/drivers/pci/controller/dwc/pcie-qcom-ep.c b/drivers/pci/controller/dwc/pcie-qcom-ep.c
> index 7940222d35f6..2aea78da9c5b 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom-ep.c
> @@ -438,8 +438,10 @@ static int qcom_pcie_perst_deassert(struct dw_pcie *pci)
> goto err_disable_resources;
> }
>
> - if (pcie_link_speed[pci->link_gen] == PCIE_SPEED_16_0GT)
> + if (pcie_link_speed[pci->link_gen] == PCIE_SPEED_16_0GT) {
> qcom_pcie_common_set_16gt_eq_settings(pci);
> + qcom_pcie_common_set_16gt_rx_margining_settings(pci);
> + }
>
> /*
> * The physical address of the MMIO region which is exposed as the BAR
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 525942f2cf98..9b3d7729b34b 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -263,8 +263,10 @@ static int qcom_pcie_start_link(struct dw_pcie *pci)
> {
> struct qcom_pcie *pcie = to_qcom_pcie(pci);
>
> - if (pcie_link_speed[pci->link_gen] == PCIE_SPEED_16_0GT)
> + if (pcie_link_speed[pci->link_gen] == PCIE_SPEED_16_0GT) {
> qcom_pcie_common_set_16gt_eq_settings(pci);
> + qcom_pcie_common_set_16gt_rx_margining_settings(pci);
> + }
>
> /* Enable Link Training state machine */
> if (pcie->cfg->ops->ltssm_enable)
> --
> 2.43.2
>
--
மணிவண்ணன் சதாசிவம்