Hi Vidya,
On Tue, Oct 31, 2017 at 09:52:48AM +0530, Vidya Sagar wrote:
> Programs T_cmrt (Commmon Mode Restore Time) and T_pwr_on (Power On)
> values to get them reflected in ASPM-L1 Sub-States capability registers
> Also adjusts internal counter values according to 19.2 MHz clk_m value
>
> Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
> ---
> V2:
> * no change in this patch
>
> drivers/pci/host/pci-tegra.c | 65 ++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 65 insertions(+)
>
> diff --git a/drivers/pci/host/pci-tegra.c b/drivers/pci/host/pci-tegra.c
> index e1526cc5d381..08da67a82a2d 100644
> --- a/drivers/pci/host/pci-tegra.c
> +++ b/drivers/pci/host/pci-tegra.c
> @@ -40,6 +40,7 @@
> #include <linux/of_pci.h>
> #include <linux/of_platform.h>
> #include <linux/pci.h>
> +#include <linux/pci-aspm.h>
> #include <linux/phy/phy.h>
> #include <linux/platform_device.h>
> #include <linux/reset.h>
> @@ -191,6 +192,27 @@
> #define RP_PRIV_XP_DL 0x494
> #define RP_PRIV_XP_DL_GEN2_UPD_FC_TSHOLD (0x1ff << 1)
>
> +#define RP_L1_PM_SUBSTATES_CTL 0xC00
> +#define RP_L1_PM_SUBSTATES_CTL_CM_RTIME_MASK (0xFF << 8)
> +#define RP_L1_PM_SUBSTATES_CTL_CM_RTIME_SHIFT 8
> +#define RP_L1_PM_SUBSTATES_CTL_T_PWRN_SCL_MASK (0x3 << 16)
> +#define RP_L1_PM_SUBSTATES_CTL_T_PWRN_SCL_SHIFT 16
> +#define RP_L1_PM_SUBSTATES_CTL_T_PWRN_VAL_MASK (0x1F << 19)
> +#define RP_L1_PM_SUBSTATES_CTL_T_PWRN_VAL_SHIFT 19
> +#define RP_L1_PM_SUBSTATES_CTL_HIDE_CAP (0x1 << 24)
> +
> +#define RP_L1_PM_SUBSTATES_1_CTL 0xC04
> +#define RP_L1_PM_SUBSTATES_1_CTL_PWR_OFF_DLY_MASK 0x1FFF
> +#define RP_L1_PM_SUBSTATES_1_CTL_PWR_OFF_DLY 0x26
> +
> +#define RP_L1_PM_SUBSTATES_2_CTL 0xC08
> +#define RP_L1_PM_SUBSTATES_2_CTL_T_L1_2_DLY_MASK 0x1FFF
> +#define RP_L1_PM_SUBSTATES_2_CTL_T_L1_2_DLY 0x4D
> +#define RP_L1_PM_SUBSTATES_2_CTL_MICROSECOND_MASK (0xFF << 13)
> +#define RP_L1_PM_SUBSTATES_2_CTL_MICROSECOND (0x13 << 13)
> +#define RP_L1_PM_SUBSTATES_2_CTL_MICROSECOND_COMP_MASK (0xF << 21)
> +#define RP_L1_PM_SUBSTATES_2_CTL_MICROSECOND_COMP (0x2 << 21)
> +
> #define RP_RX_HDR_LIMIT 0xe00
> #define RP_RX_HDR_LIMIT_PW_MASK (0xff << 8)
> #define RP_RX_HDR_LIMIT_PW (0x0e << 8)
> @@ -331,6 +353,7 @@ struct tegra_pcie_soc {
> bool program_deskew_time;
> bool updateFC_threshold;
> bool has_aspm_l1;
> + bool has_aspm_l1ss;
> };
>
> static inline struct tegra_msi *to_tegra_msi(struct msi_controller *chip)
> @@ -423,6 +446,12 @@ static inline u32 pads_readl(struct tegra_pcie *pcie, unsigned long offset)
> return readl(pcie->pads + offset);
> }
>
> +u32 pcie_aspm_get_ltr_l_1_2_threshold(void)
> +{
> + /* LTR L1.2 Threshold = 55us for all ports */
> + return ((0x37 << 16) | (0x02 << 29));
I know you've already worked through this, but let me think out loud
to try to figure this out myself.
ASPM defines Link power states L0, L0s, and L1. L1 PM Substates
extend that by adding L1.1 and L1.2. L1.2 presumably uses less power
and has a longer exit delay than L1.1 [sec 5.5].
Ports that support L1.2 must support Latency Tolerance Reporting (LTR)
[sec 6.18]. When LTR is enabled, a device periodically sends LTR
messages.
When ASPM puts a Link into L1, it chooses either L1.1 or L1.2 based on
LTR_L1.2_THRESHOLD and recent LTR messages. If there's no LTR
information it looks like LTR_L1.2_THRESHOLD doesn't matter and it
always chooses L1.2 [sec 5.5.1].
I don't see anything that writes PCI_EXP_DEVCTL2_LTR_EN, so I don't
think Linux ever enables LTR. Some BIOSes apparently enable it
(Google for "LTR enabled").
1) It seems like the LTR_L1.2_THRESHOLD value should be computed based
on the latency requirements of downstream devices. How did you
come up with 55us?
2) The spec requires [sec 5.5.4] that LTR_L1.2_THRESHOLD at both ends
of a Link be the same, but as far as I can see, there's no
requirement that it be the same across the whole system, so this
interface doesn't seem like quite the right approach.
3) We must support kernels with multiple host bridge drivers compiled
in, and the weak/strong symbol approach doesn't support using the
correct version, e.g., if we merge this patch, every system
containing the tegra driver would use this function, even if the
hardware had a different host bridge. Also, if another driver
implemented its own version, we'd have duplicate symbols.
> /*
> * The configuration space mapping on Tegra is somewhat similar to the ECAM
> * defined by PCIe. However it deviates a bit in how the 4 bits for extended
> @@ -2262,6 +2291,37 @@ static void tegra_pcie_apply_sw_fixup(struct tegra_pcie_port *port)
> value |= RP_VEND_XP_UPDATE_FC_THRESHOLD_T210;
> writel(value, port->base + RP_VEND_XP);
> }
> +
> + if (soc->has_aspm_l1ss) {
> + /* Set Common Mode Restore Time to 30us */
> + value = readl(port->base + RP_L1_PM_SUBSTATES_CTL);
> + value &= ~RP_L1_PM_SUBSTATES_CTL_CM_RTIME_MASK;
> + value |= (0x1E << RP_L1_PM_SUBSTATES_CTL_CM_RTIME_SHIFT);
> + writel(value, port->base + RP_L1_PM_SUBSTATES_CTL);
> +
> + /* set T_Power_On to 70us */
> + value = readl(port->base + RP_L1_PM_SUBSTATES_CTL);
> + value &= ~(RP_L1_PM_SUBSTATES_CTL_T_PWRN_SCL_MASK |
> + RP_L1_PM_SUBSTATES_CTL_T_PWRN_VAL_MASK);
> + value |= (1 << RP_L1_PM_SUBSTATES_CTL_T_PWRN_SCL_SHIFT) |
> + (7 << RP_L1_PM_SUBSTATES_CTL_T_PWRN_VAL_SHIFT);
> + writel(value, port->base + RP_L1_PM_SUBSTATES_CTL);
> +
> + /* Following is based on clk_m being 19.2 MHz */
> + value = readl(port->base + RP_L1_PM_SUBSTATES_1_CTL);
> + value &= ~RP_L1_PM_SUBSTATES_1_CTL_PWR_OFF_DLY_MASK;
> + value |= RP_L1_PM_SUBSTATES_1_CTL_PWR_OFF_DLY;
> + writel(value, port->base + RP_L1_PM_SUBSTATES_1_CTL);
> +
> + value = readl(port->base + RP_L1_PM_SUBSTATES_2_CTL);
> + value &= ~RP_L1_PM_SUBSTATES_2_CTL_T_L1_2_DLY_MASK;
> + value |= RP_L1_PM_SUBSTATES_2_CTL_T_L1_2_DLY;
> + value &= ~RP_L1_PM_SUBSTATES_2_CTL_MICROSECOND_MASK;
> + value |= RP_L1_PM_SUBSTATES_2_CTL_MICROSECOND;
> + value &= ~RP_L1_PM_SUBSTATES_2_CTL_MICROSECOND_COMP_MASK;
> + value |= RP_L1_PM_SUBSTATES_2_CTL_MICROSECOND_COMP;
> + writel(value, port->base + RP_L1_PM_SUBSTATES_2_CTL);
> + }
> }
> /*
> * FIXME: If there are no PCIe cards attached, then calling this function
> @@ -2403,6 +2463,7 @@ static const struct tegra_pcie_soc tegra20_pcie = {
> .program_deskew_time = false,
> .updateFC_threshold = false,
> .has_aspm_l1 = false,
> + .has_aspm_l1ss = false,
> };
>
> static const struct tegra_pcie_soc tegra30_pcie = {
> @@ -2425,6 +2486,7 @@ static const struct tegra_pcie_soc tegra30_pcie = {
> .program_deskew_time = false,
> .updateFC_threshold = false,
> .has_aspm_l1 = true,
> + .has_aspm_l1ss = false,
> };
>
> static const struct tegra_pcie_soc tegra124_pcie = {
> @@ -2446,6 +2508,7 @@ static const struct tegra_pcie_soc tegra124_pcie = {
> .program_deskew_time = false,
> .updateFC_threshold = false,
> .has_aspm_l1 = true,
> + .has_aspm_l1ss = false,
> };
>
> static const struct tegra_pcie_soc tegra210_pcie = {
> @@ -2475,6 +2538,7 @@ static const struct tegra_pcie_soc tegra210_pcie = {
> .program_deskew_time = true,
> .updateFC_threshold = true,
> .has_aspm_l1 = true,
> + .has_aspm_l1ss = true,
> };
>
> static const struct tegra_pcie_soc tegra186_pcie = {
> @@ -2497,6 +2561,7 @@ static const struct tegra_pcie_soc tegra186_pcie = {
> .program_deskew_time = false,
> .updateFC_threshold = false,
> .has_aspm_l1 = true,
> + .has_aspm_l1ss = true,
> };
>
> static const struct of_device_id tegra_pcie_of_match[] = {
> --
> 2.7.4
>
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