linux-kernel - Re: [PATCH v2 3/3] PCI: qcom: Add rx margining settings for gen4

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Date: Tue, 2 Apr 2024 11:17:45 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Shashank Babu Chinta Venkata <quic_schintav@...cinc.com>
Cc: agross@...nel.org, andersson@...nel.org, konrad.dybcio@...aro.org,
	quic_msarkar@...cinc.com, quic_kraravin@...cinc.com,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Jingoo Han <jingoohan1@...il.com>,
	Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Serge Semin <fancer.lancer@...il.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	Conor Dooley <conor.dooley@...rochip.com>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 3/3] PCI: qcom: Add rx margining settings for gen4

On Wed, Mar 20, 2024 at 12:14:47AM -0700, Shashank Babu Chinta Venkata wrote:
> Add rx margining settings for gen4 operation.
> 

What is 'rx margining'? As mentioned in the previous patch, use 16 GT/s.

> Signed-off-by: Shashank Babu Chinta Venkata <quic_schintav@...cinc.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware.h | 23 +++++++++++++
>  drivers/pci/controller/dwc/pcie-qcom-cmn.c   | 35 ++++++++++++++++++++
>  drivers/pci/controller/dwc/pcie-qcom-cmn.h   | 11 +++++-
>  drivers/pci/controller/dwc/pcie-qcom-ep.c    |  4 ++-
>  drivers/pci/controller/dwc/pcie-qcom.c       |  4 ++-
>  5 files changed, 74 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 064744bfe35a..ce1c5f9c406a 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -206,6 +206,29 @@
>  
>  #define PCIE_PL_CHK_REG_ERR_ADDR			0xB28
>  
> +/*
> + * GEN4 lane margining register definitions
> + */
> +#define GEN4_LANE_MARGINING_1_OFF		0xb80
> +#define MARGINING_MAX_VOLTAGE_OFFSET_MASK	GENMASK(29, 24)
> +#define MARGINING_NUM_VOLTAGE_STEPS_MASK	GENMASK(22, 16)
> +#define MARGINING_MAX_TIMING_OFFSET_MASK	GENMASK(13, 8)
> +#define MARGINING_NUM_TIMING_STEPS_MASK		GENMASK(5, 0)
> +#define MARGINING_MAX_VOLTAGE_OFFSET_SHIFT	24
> +#define MARGINING_NUM_VOLTAGE_STEPS_SHIFT	16
> +#define MARGINING_MAX_TIMING_OFFSET_SHIFT	8
> +
> +#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_MASK			GENMASK(20, 16)
> +#define MARGINING_SAMPLE_RATE_TIMING_MASK	GENMASK(13, 8)
> +#define MARGINING_SAMPLE_RATE_VOLTAGE_MASK	GENMASK(5, 0)
> +#define MARGINING_MAXLANES_SHIFT		16
> +#define MARGINING_SAMPLE_RATE_TIMING_SHIFT	8

Add a newline

>  /*
>   * 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-cmn.c b/drivers/pci/controller/dwc/pcie-qcom-cmn.c
> index 208a55e8e9a1..bf6b27ee8327 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom-cmn.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom-cmn.c
> @@ -53,6 +53,41 @@ void qcom_pcie_cmn_set_16gt_eq_settings(struct dw_pcie *pci)
>  }
>  EXPORT_SYMBOL_GPL(qcom_pcie_cmn_set_16gt_eq_settings);
>  
> +void qcom_pcie_cmn_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_MASK;
> +	reg |= (MARGINING_MAX_VOLTAGE_OFFSET_VAL <<
> +		MARGINING_MAX_VOLTAGE_OFFSET_SHIFT);

Same comment as previous patch to use FIELD_* macros.

- Mani

-- 
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