[PATCH v4 2/5] PCI: brcmstb: Configure HW CLKREQ# mode appropriate for downstream device
Stefan Wahren
stefan.wahren at i2se.com
Tue May 2 23:09:32 PDT 2023
Am 29.04.23 um 00:34 schrieb Jim Quinlan:
> The Broadcom STB/CM PCIe HW core, which is also used in RPi SOCs, must be
> deliberately set by the RC probe() into one of three mutually exclusive
> modes:
>
> (a) No CLKREQ# expected or required, refclk is always available.
> (b) CLKREQ# is expected to be driven by downstream device when needed.
> (c) Bidirectional CLKREQ# for L1SS capable devices.
>
> Previously, only (b) was supported by the driver, as almost all STB/CM
> boards operate in this mode. But now there is interest in activating L1SS
> power savings from STB/CM customers, and also interest in accommodating
> mode (a) for designs such as the RPi CM4 with IO board.
>
> The HW+driver is able to tell us when mode (a) or (b) is needed. All
> devices should be functional using the RC-driver selected (a) or (b) mode.
> For those with L1SS-capable devices that desire the power savings that come
> with mode (c) we rely on the DT prop "brcm,enable-l1ss". It would be nice
> to do this automatically but there is no easy way to determine this at the
> time the PCI RC driver executes its probe(). Using this mode only makes
> sense when the downstream device is L1SS-capable and the OS has been
> configured to activate L1SS (e.g. policy==powersupersave).
>
> The "brcm,enable-l1ss" property has already been in use by Raspian Linux,
> but this implementation adds more details and discerns between (a) and (b)
> automatically.
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217276
> Tested-by: Florian Fainelli <f.fainelli at gmail.com>
> Signed-off-by: Jim Quinlan <jim2101024 at gmail.com>
> ---
> drivers/pci/controller/pcie-brcmstb.c | 69 +++++++++++++++++++++++----
> 1 file changed, 59 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> index edf283e2b5dd..c4b076ea5180 100644
> --- a/drivers/pci/controller/pcie-brcmstb.c
> +++ b/drivers/pci/controller/pcie-brcmstb.c
> @@ -48,10 +48,17 @@
> #define PCIE_RC_CFG_PRIV1_LINK_CAPABILITY 0x04dc
> #define PCIE_RC_CFG_PRIV1_LINK_CAPABILITY_ASPM_SUPPORT_MASK 0xc00
>
> +#define PCIE_RC_CFG_PRIV1_ROOT_CAP 0x4f8
> +#define PCIE_RC_CFG_PRIV1_ROOT_CAP_L1SS_MODE_MASK 0xf8
> +
> #define PCIE_RC_DL_MDIO_ADDR 0x1100
> #define PCIE_RC_DL_MDIO_WR_DATA 0x1104
> #define PCIE_RC_DL_MDIO_RD_DATA 0x1108
>
> +#define PCIE_0_RC_PL_PHY_DBG_CLKREQ2_0 0x1e30
> +#define CLKREQ2_0_CLKREQ_IN_CNT_MASK 0x3f000000
> +#define CLKREQ2_0_CLKREQ_IN_MASK 0x40000000
> +
> #define PCIE_MISC_MISC_CTRL 0x4008
> #define PCIE_MISC_MISC_CTRL_PCIE_RCB_64B_MODE_MASK 0x80
> #define PCIE_MISC_MISC_CTRL_PCIE_RCB_MPS_MODE_MASK 0x400
> @@ -121,9 +128,12 @@
>
> #define PCIE_MISC_HARD_PCIE_HARD_DEBUG 0x4204
> #define PCIE_MISC_HARD_PCIE_HARD_DEBUG_CLKREQ_DEBUG_ENABLE_MASK 0x2
> +#define PCIE_MISC_HARD_PCIE_HARD_DEBUG_L1SS_ENABLE_MASK 0x200000
> #define PCIE_MISC_HARD_PCIE_HARD_DEBUG_SERDES_IDDQ_MASK 0x08000000
> #define PCIE_BMIPS_MISC_HARD_PCIE_HARD_DEBUG_SERDES_IDDQ_MASK 0x00800000
> -
> +#define PCIE_CLKREQ_MASK \
> + (PCIE_MISC_HARD_PCIE_HARD_DEBUG_CLKREQ_DEBUG_ENABLE_MASK | \
> + PCIE_MISC_HARD_PCIE_HARD_DEBUG_L1SS_ENABLE_MASK)
>
> #define PCIE_INTR2_CPU_BASE 0x4300
> #define PCIE_MSI_INTR2_BASE 0x4500
> @@ -1024,13 +1034,58 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
> return 0;
> }
>
> +static void brcm_config_clkreq(struct brcm_pcie *pcie)
> +{
> + bool l1ss = of_property_read_bool(pcie->np, "brcm,enable-l1ss");
> + void __iomem *base = pcie->base;
> + u32 clkreq_set, tmp = readl(base + PCIE_0_RC_PL_PHY_DBG_CLKREQ2_0);
> + bool clkreq_in_seen;
> +
> + /*
> + * We have "seen" CLKREQ# if it is asserted or has been in the past.
> + * Note that the CLKREQ_IN_MASK is 1 if CLKREQ# is asserted.
> + */
> + clkreq_in_seen = !!(tmp & CLKREQ2_0_CLKREQ_IN_MASK) ||
> + !!FIELD_GET(CLKREQ2_0_CLKREQ_IN_CNT_MASK, tmp);
> +
> + /* Start with safest setting where we provide refclk regardless */
> + clkreq_set = readl(pcie->base + PCIE_MISC_HARD_PCIE_HARD_DEBUG) &
> + ~PCIE_CLKREQ_MASK;
> +
> + if (l1ss && IS_ENABLED(CONFIG_PCIEASPM)) {
> + /*
> + * Note: For boards using a mini-card connector, this mode
> + * may not meet the TCRLon maximum time of 400ns, as
> + * specified in 3.2.5.2.5 of the PCI Express Mini CEM 2.0
> + * specification.
> + */
> + clkreq_set |= PCIE_MISC_HARD_PCIE_HARD_DEBUG_L1SS_ENABLE_MASK;
> + dev_info(pcie->dev, "bi-dir CLKREQ# for L1SS power savings");
Please append the missing newline to the log message
> + } else {
> + if (clkreq_in_seen && IS_ENABLED(CONFIG_PCIEASPM)) {
> + clkreq_set |= PCIE_MISC_HARD_PCIE_HARD_DEBUG_CLKREQ_DEBUG_ENABLE_MASK;
> + dev_info(pcie->dev, "uni-dir CLKREQ# for L0s, L1 ASPM\n");
> + } else {
> + dev_info(pcie->dev, "CLKREQ# ignored; no ASPM\n");
> + /* Might as well unadvertise ASPM */
> + tmp = readl(base + PCIE_RC_CFG_PRIV1_LINK_CAPABILITY) &
> + ~PCIE_RC_CFG_PRIV1_LINK_CAPABILITY_ASPM_SUPPORT_MASK;
> + writel(tmp, base + PCIE_RC_CFG_PRIV1_LINK_CAPABILITY);
> + }
> + /* Setting the field to 2 unadvertises L1SS support */
> + tmp = readl(base + PCIE_RC_CFG_PRIV1_ROOT_CAP);
> + u32p_replace_bits(&tmp, 2, PCIE_RC_CFG_PRIV1_ROOT_CAP_L1SS_MODE_MASK);
> + writel(tmp, base + PCIE_RC_CFG_PRIV1_ROOT_CAP);
> + }
> + writel(clkreq_set, pcie->base + PCIE_MISC_HARD_PCIE_HARD_DEBUG);
> +}
> +
> static int brcm_pcie_start_link(struct brcm_pcie *pcie)
> {
> struct device *dev = pcie->dev;
> void __iomem *base = pcie->base;
> u16 nlw, cls, lnksta;
> bool ssc_good = false;
> - u32 tmp;
> int ret, i;
>
> /* Unassert the fundamental reset */
> @@ -1055,6 +1110,8 @@ static int brcm_pcie_start_link(struct brcm_pcie *pcie)
> return -ENODEV;
> }
>
> + brcm_config_clkreq(pcie);
> +
> if (pcie->gen)
> brcm_pcie_set_gen(pcie, pcie->gen);
>
> @@ -1073,14 +1130,6 @@ static int brcm_pcie_start_link(struct brcm_pcie *pcie)
> pci_speed_string(pcie_link_speed[cls]), nlw,
> ssc_good ? "(SSC)" : "(!SSC)");
>
> - /*
> - * Refclk from RC should be gated with CLKREQ# input when ASPM L0s,L1
> - * is enabled => setting the CLKREQ_DEBUG_ENABLE field to 1.
> - */
> - tmp = readl(base + PCIE_MISC_HARD_PCIE_HARD_DEBUG);
> - tmp |= PCIE_MISC_HARD_PCIE_HARD_DEBUG_CLKREQ_DEBUG_ENABLE_MASK;
> - writel(tmp, base + PCIE_MISC_HARD_PCIE_HARD_DEBUG);
> -
> return 0;
> }
>
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