linux-kernel - Re: [PATCH 07/12] pcie: qcom: add tx term offset support

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Message-ID: <20200401204007.GG254911@minitux>
Date:   Wed, 1 Apr 2020 13:40:07 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Ansuel Smith <ansuelsmth@...il.com>
Cc:     Stanimir Varbanov <svarbanov@...sol.com>,
        Sham Muthayyan <smuthayy@...eaurora.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Murray <amurray@...goodpenguin.co.uk>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/12] pcie: qcom: add tx term offset support

On Fri 20 Mar 11:34 PDT 2020, Ansuel Smith wrote:

> From: Sham Muthayyan <smuthayy@...eaurora.org>
> 
> Add tx term offset support to pcie qcom driver
> need in some revision of the ipq806x soc
> 
> Signed-off-by: Sham Muthayyan <smuthayy@...eaurora.org>
> Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 61 ++++++++++++++++++++++----
>  1 file changed, 52 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index ecc22fd27ea6..8009e3117765 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -45,7 +45,13 @@
>  #define PCIE_CAP_CPL_TIMEOUT_DISABLE		0x10
>  
>  #define PCIE20_PARF_PHY_CTRL			0x40
> +#define PHY_CTRL_PHY_TX0_TERM_OFFSET_MASK	(0x1f << 16)
> +#define PHY_CTRL_PHY_TX0_TERM_OFFSET(x)		(x << 16)
> +
>  #define PCIE20_PARF_PHY_REFCLK			0x4C
> +#define REF_SSP_EN				BIT(16)
> +#define REF_USE_PAD				BIT(12)
> +
>  #define PCIE20_PARF_DBI_BASE_ADDR		0x168
>  #define PCIE20_PARF_SLV_ADDR_SPACE_SIZE		0x16C
>  #define PCIE20_PARF_MHI_CLOCK_RESET_CTRL	0x174
> @@ -77,6 +83,18 @@
>  #define DBI_RO_WR_EN				1
>  
>  #define PERST_DELAY_US				1000
> +/* PARF registers */
> +#define PCIE20_PARF_PCS_DEEMPH			0x34
> +#define PCS_DEEMPH_TX_DEEMPH_GEN1(x)		(x << 16)
> +#define PCS_DEEMPH_TX_DEEMPH_GEN2_3_5DB(x)	(x << 8)
> +#define PCS_DEEMPH_TX_DEEMPH_GEN2_6DB(x)	(x << 0)
> +
> +#define PCIE20_PARF_PCS_SWING			0x38
> +#define PCS_SWING_TX_SWING_FULL(x)		(x << 8)
> +#define PCS_SWING_TX_SWING_LOW(x)		(x << 0)
> +
> +#define PCIE20_PARF_CONFIG_BITS			0x50
> +#define PHY_RX0_EQ(x)				(x << 24)
>  
>  #define PCIE20_v3_PARF_SLV_ADDR_SPACE_SIZE	0x358
>  #define SLV_ADDR_SPACE_SZ			0x10000000
> @@ -97,6 +115,7 @@ struct qcom_pcie_resources_2_1_0 {
>  	struct reset_control *phy_reset;
>  	struct reset_control *ext_reset;
>  	struct regulator_bulk_data supplies[QCOM_PCIE_2_1_0_MAX_SUPPLY];
> +	uint8_t phy_tx0_term_offset;
>  };
>  
>  struct qcom_pcie_resources_1_0_0 {
> @@ -184,6 +203,16 @@ struct qcom_pcie {
>  
>  #define to_qcom_pcie(x)		dev_get_drvdata((x)->dev)
>  
> +static inline void
> +writel_masked(void __iomem *addr, u32 clear_mask, u32 set_mask)
> +{
> +	u32 val = readl(addr);
> +
> +	val &= ~clear_mask;
> +	val |= set_mask;
> +	writel(val, addr);
> +}
> +
>  static void qcom_ep_reset_assert(struct qcom_pcie *pcie)
>  {
>  	gpiod_set_value_cansleep(pcie->reset, 1);
> @@ -277,6 +306,10 @@ static int qcom_pcie_get_resources_2_1_0(struct qcom_pcie *pcie)
>  	if (IS_ERR(res->ext_reset))
>  		return PTR_ERR(res->ext_reset);
>  
> +	if (of_property_read_u8(dev->of_node, "phy-tx0-term-offset",
> +				&res->phy_tx0_term_offset))
> +		res->phy_tx0_term_offset = 0;

The appropriate way is to encode differences in hardware is to use
different compatibles for the two different versions of the hardware.

Regards,
Bjorn

> +
>  	res->phy_reset = devm_reset_control_get_exclusive(dev, "phy");
>  	return PTR_ERR_OR_ZERO(res->phy_reset);
>  }
> @@ -304,7 +337,6 @@ static int qcom_pcie_init_2_1_0(struct qcom_pcie *pcie)
>  	struct qcom_pcie_resources_2_1_0 *res = &pcie->res.v2_1_0;
>  	struct dw_pcie *pci = pcie->pci;
>  	struct device *dev = pci->dev;
> -	u32 val;
>  	int ret;
>  
>  	ret = reset_control_assert(res->ahb_reset);
> @@ -355,15 +387,26 @@ static int qcom_pcie_init_2_1_0(struct qcom_pcie *pcie)
>  		goto err_deassert_ahb;
>  	}
>  
> -	/* enable PCIe clocks and resets */
> -	val = readl(pcie->parf + PCIE20_PARF_PHY_CTRL);
> -	val &= ~BIT(0);
> -	writel(val, pcie->parf + PCIE20_PARF_PHY_CTRL);
> +	writel_masked(pcie->parf + PCIE20_PARF_PHY_CTRL, BIT(0), 0);
> +
> +	/* Set Tx termination offset */
> +	writel_masked(pcie->parf + PCIE20_PARF_PHY_CTRL,
> +		      PHY_CTRL_PHY_TX0_TERM_OFFSET_MASK,
> +		      PHY_CTRL_PHY_TX0_TERM_OFFSET(res->phy_tx0_term_offset));
> +
> +	/* PARF programming */
> +	writel(PCS_DEEMPH_TX_DEEMPH_GEN1(0x18) |
> +	       PCS_DEEMPH_TX_DEEMPH_GEN2_3_5DB(0x18) |
> +	       PCS_DEEMPH_TX_DEEMPH_GEN2_6DB(0x22),
> +	       pcie->parf + PCIE20_PARF_PCS_DEEMPH);
> +	writel(PCS_SWING_TX_SWING_FULL(0x78) |
> +	       PCS_SWING_TX_SWING_LOW(0x78),
> +	       pcie->parf + PCIE20_PARF_PCS_SWING);
> +	writel(PHY_RX0_EQ(0x4), pcie->parf + PCIE20_PARF_CONFIG_BITS);
>  
> -	/* enable external reference clock */
> -	val = readl(pcie->parf + PCIE20_PARF_PHY_REFCLK);
> -	val |= BIT(16);
> -	writel(val, pcie->parf + PCIE20_PARF_PHY_REFCLK);
> +	/* Enable reference clock */
> +	writel_masked(pcie->parf + PCIE20_PARF_PHY_REFCLK,
> +		      REF_USE_PAD, REF_SSP_EN);
>  
>  	ret = reset_control_deassert(res->phy_reset);
>  	if (ret) {
> -- 
> 2.25.1
>