Re: [PATCH v11 06/11] PCI: brcmstb: Add control of rescal reset

Lorenzo Pieralisi
2020-09-08T16:25:31Z

On Mon, Aug 24, 2020 at 03:30:19PM -0400, Jim Quinlan wrote:
> From: Jim Quinlan <jquinlan@broadcom.com>
>
> Some STB chips have a special purpose reset controller named RESCAL (reset
> calibration). The PCIe HW can now control RESCAL to start and stop its
> operation. On probe(), the RESCAL is deasserted and the driver goes
> through the sequence of setting registers and reading status in order to
> start the internal PHY that is required for the PCIe.
>
> Signed-off-by: Jim Quinlan <jquinlan@broadcom.com>
> Acked-by: Florian Fainelli <f.fainelli@gmail.com>
> ---
> drivers/pci/controller/pcie-brcmstb.c | 82 ++++++++++++++++++++++++++-
> 1 file changed, 81 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> index acf2239b0251..041b8d109563 100644
> --- a/drivers/pci/controller/pcie-brcmstb.c
> +++ b/drivers/pci/controller/pcie-brcmstb.c
> @@ -23,6 +23,7 @@
> #include <linux/of_platform.h>
> #include <linux/pci.h>
> #include <linux/printk.h>
> +#include <linux/reset.h>
> #include <linux/sizes.h>
> #include <linux/slab.h>
> #include <linux/string.h>
> @@ -158,6 +159,16 @@
> #define DATA_ADDR(pcie) (pcie->reg_offsets[EXT_CFG_DATA])
> #define PCIE_RGR1_SW_INIT_1(pcie) (pcie->reg_offsets[RGR1_SW_INIT_1])
>
> +/* Rescal registers */
> +#define PCIE_DVT_PMU_PCIE_PHY_CTRL 0xc700
> +#define PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_NFLDS 0x3
> +#define PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_DIG_RESET_MASK 0x4
> +#define PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_DIG_RESET_SHIFT 0x2
> +#define PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_RESET_MASK 0x2
> +#define PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_RESET_SHIFT 0x1
> +#define PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_PWRDN_MASK 0x1
> +#define PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_PWRDN_SHIFT 0x0
> +
> enum {
> RGR1_SW_INIT_1,
> EXT_CFG_INDEX,
> @@ -247,6 +258,7 @@ struct brcm_pcie {
> const int *reg_offsets;
> const int *reg_field_info;
> enum pcie_type type;
> + struct reset_control *rescal;
> };
>
> /*
> @@ -965,6 +977,47 @@ static void brcm_pcie_enter_l23(struct brcm_pcie *pcie)
> dev_err(pcie->dev, "failed to enter low-power link state\n");
> }
>
> +static int brcm_phy_cntl(struct brcm_pcie *pcie, const int start)
> +{
> + static const u32 shifts[PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_NFLDS] = {
> + PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_PWRDN_SHIFT,
> + PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_RESET_SHIFT,
> + PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_DIG_RESET_SHIFT,};
> + static const u32 masks[PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_NFLDS] = {
> + PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_PWRDN_MASK,
> + PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_RESET_MASK,
> + PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_DIG_RESET_MASK,};
> + const int beg = start ? 0 : PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_NFLDS - 1;
> + const int end = start ? PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_NFLDS : -1;
> + u32 tmp, combined_mask = 0;
> + u32 val = !!start;

Quick note: I think it would be nicer to init val within the loop
below (IIUC how this works):

val = start ? BIT_MASK(shifts[i]) : 0;

and then use it in the tmp computation but I leave it up to you.

Lorenzo

> + void __iomem *base = pcie->base;
> + int i;
> +
> + for (i = beg; i != end; start ? i++ : i--) {
> + tmp = readl(base + PCIE_DVT_PMU_PCIE_PHY_CTRL);
> + tmp = (tmp & ~masks[i]) | ((val << shifts[i]) & masks[i]);
> + writel(tmp, base + PCIE_DVT_PMU_PCIE_PHY_CTRL);
> + usleep_range(50, 200);
> + combined_mask |= masks[i];
> + }
> +
> + tmp = readl(base + PCIE_DVT_PMU_PCIE_PHY_CTRL);
> + val = start ? combined_mask : 0;
> +
> + return (tmp & combined_mask) == val ? 0 : -EIO;
> +}
> +
> +static inline int brcm_phy_start(struct brcm_pcie *pcie)
> +{
> + return pcie->rescal ? brcm_phy_cntl(pcie, 1) : 0;
> +}
> +
> +static inline int brcm_phy_stop(struct brcm_pcie *pcie)
> +{
> + return pcie->rescal ? brcm_phy_cntl(pcie, 0) : 0;
> +}
> +
> static void brcm_pcie_turn_off(struct brcm_pcie *pcie)
> {
> void __iomem *base = pcie->base;
> @@ -992,11 +1045,15 @@ static void brcm_pcie_turn_off(struct brcm_pcie *pcie)
> static int brcm_pcie_suspend(struct device *dev)
> {
> struct brcm_pcie *pcie = dev_get_drvdata(dev);
> + int ret;
>
> brcm_pcie_turn_off(pcie);
> + ret = brcm_phy_stop(pcie);
> + if (ret)
> + dev_err(pcie->dev, "failed to stop phy\n");
> clk_disable_unprepare(pcie->clk);
>
> - return 0;
> + return ret;
> }
>
> static int brcm_pcie_resume(struct device *dev)
> @@ -1009,6 +1066,12 @@ static int brcm_pcie_resume(struct device *dev)
> base = pcie->base;
> clk_prepare_enable(pcie->clk);
>
> + ret = brcm_phy_start(pcie);
> + if (ret) {
> + dev_err(pcie->dev, "failed to start phy\n");
> + return ret;
> + }
> +
> /* Take bridge out of reset so we can access the SERDES reg */
> brcm_pcie_bridge_sw_init_set(pcie, 0);
>
> @@ -1034,6 +1097,9 @@ static void __brcm_pcie_remove(struct brcm_pcie *pcie)
> {
> brcm_msi_remove(pcie);
> brcm_pcie_turn_off(pcie);
> + if (brcm_phy_stop(pcie))
> + dev_err(pcie->dev, "failed to stop phy\n");
> + reset_control_assert(pcie->rescal);
> clk_disable_unprepare(pcie->clk);
> }
>
> @@ -1112,6 +1178,20 @@ static int brcm_pcie_probe(struct platform_device *pdev)
> dev_err(&pdev->dev, "could not enable clock\n");
> return ret;
> }
> + pcie->rescal = devm_reset_control_get_optional_shared(&pdev->dev, "rescal");
> + if (IS_ERR(pcie->rescal))
> + return PTR_ERR(pcie->rescal);
> +
> + ret = reset_control_deassert(pcie->rescal);
> + if (ret)
> + dev_err(&pdev->dev, "failed to deassert 'rescal'\n");
> +
> + ret = brcm_phy_start(pcie);
> + if (ret) {
> + dev_err(pcie->dev, "failed to start phy\n");
> + reset_control_assert(pcie->rescal);
> + return ret;
> + }
>
> ret = brcm_pcie_setup(pcie);
> if (ret)
> --
> 2.17.1
>