On Mon, 28 Oct 2024, Mika Kahola <mika.kahola@xxxxxxxxx> wrote:
> There is a HW issue that arises when there are race conditions
> between TCSS entering/exiting TC7 or TC10 states while the
> driver is asserting/deasserting TCSS power request. As a
> workaround, Display driver will implement a mailbox sequence
> to ensure that the TCSS is in TC0 when TCSS power request is
> asserted/deasserted.
>
> The sequence is the following
>
> 1. Read mailbox command status and wait until run/busy bit is
> clear
> 2. Write mailbox data value '1' for power request asserting
> and '0' for power request deasserting
> 3. Write mailbox command run/busy bit and command value with 0x1
> 4. Read mailbox command and wait until run/busy bit is clear
> before continuing power request.
>
> v2: Rename WA function (Gustavo)
> Limit WA only for PTL platform with a TODO note (Gustavo)
> Add TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY for clarity when writing
> register data (Gustavo)
> Move register defs from i915_reg.h to intel_cx0_phy_regs.h (Gustavo)
>
> Signed-off-by: Mika Kahola <mika.kahola@xxxxxxxxx>
> ---
> .../gpu/drm/i915/display/intel_cx0_phy_regs.h | 7 +++
> drivers/gpu/drm/i915/display/intel_tc.c | 46 +++++++++++++++++++
> 2 files changed, 53 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_cx0_phy_regs.h b/drivers/gpu/drm/i915/display/intel_cx0_phy_regs.h
> index ab3ae110b68f..e46c07cd20e0 100644
> --- a/drivers/gpu/drm/i915/display/intel_cx0_phy_regs.h
> +++ b/drivers/gpu/drm/i915/display/intel_cx0_phy_regs.h
> @@ -363,4 +363,11 @@
> #define HDMI_DIV_MASK REG_GENMASK16(2, 0)
> #define HDMI_DIV(val) REG_FIELD_PREP16(HDMI_DIV_MASK, val)
>
> +#define TCSS_DISP_MAILBOX_IN_CMD _MMIO(0x161300)
> +#define TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY REG_BIT(31)
> +#define TCSS_DISP_MAILBOX_IN_CMD_CMD_MASK REG_GENMASK(7, 0)
> +#define TCSS_DISP_MAILBOX_IN_CMD_DATA(x) TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY | \
> + REG_FIELD_PREP(TCSS_DISP_MAILBOX_IN_CMD_CMD_MASK, (x))
> +#define TCSS_DISP_MAILBOX_IN_DATA _MMIO(0x161304)
> +
> #endif /* __INTEL_CX0_REG_DEFS_H__ */
> diff --git a/drivers/gpu/drm/i915/display/intel_tc.c b/drivers/gpu/drm/i915/display/intel_tc.c
> index 6f2ee7dbc43b..924c3ff04eb6 100644
> --- a/drivers/gpu/drm/i915/display/intel_tc.c
> +++ b/drivers/gpu/drm/i915/display/intel_tc.c
> @@ -1013,6 +1013,45 @@ xelpdp_tc_phy_wait_for_tcss_power(struct intel_tc_port *tc, bool enabled)
> return true;
> }
>
> +static bool wa_tcss_power_request_assert(struct drm_i915_private *i915,
Please use struct intel_display *display for new code.
> + bool enable)
> +{
> + /*
> + * Limit to PTL only
> + * TODO: Add check for PICA IP and use that instead limiting WA for
> + * platform
> + */
> + if (DISPLAY_VER(i915) != 30)
s/i915/display/
> + return true;
> +
> + /* check if mailbox is running busy */
> + if (intel_de_wait_for_clear(i915, TCSS_DISP_MAILBOX_IN_CMD,
> + TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY, 10)) {
s/i915/display/
> + drm_dbg_kms(&i915->drm,
display->drm
Ditto below, this function doesn't need struct drm_i915_private for
anything.
> + "Power request assert WA timeout waiting for TCSS mailbox run/busy bit to clear\n");
> + return false;
> + }
> +
> + if (enable)
> + intel_de_write(i915, TCSS_DISP_MAILBOX_IN_DATA, 1);
> + else
> + intel_de_write(i915, TCSS_DISP_MAILBOX_IN_DATA, 0);
> +
> + intel_de_write(i915, TCSS_DISP_MAILBOX_IN_CMD,
> + TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY |
> + TCSS_DISP_MAILBOX_IN_CMD_DATA(0x1));
> +
> + /* wait to clear mailbox running busy bit before continuing */
> + if (intel_de_wait_for_clear(i915, TCSS_DISP_MAILBOX_IN_CMD,
> + TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY, 10)) {
> + drm_dbg_kms(&i915->drm,
> + "Power request assert WA timeout waiting for TCSS mailbox run/busy bit to clear\n");
> + return false;
> + }
> +
> + return true;
> +}
> +
> static void __xelpdp_tc_phy_enable_tcss_power(struct intel_tc_port *tc, bool enable)
> {
> struct drm_i915_private *i915 = tc_to_i915(tc);
> @@ -1022,6 +1061,13 @@ static void __xelpdp_tc_phy_enable_tcss_power(struct intel_tc_port *tc, bool ena
>
> assert_tc_cold_blocked(tc);
>
> + /*
> + * Gfx driver workaround for PTL tcss_rxdetect_clkswb_req/ack handshake
> + * violation when pwwreq= 0->1 during TC7/10 entry
> + */
> + drm_WARN_ON(&i915->drm,
> + !wa_tcss_power_request_assert(i915, enable));
> +
> val = intel_de_read(i915, reg);
> if (enable)
> val |= XELPDP_TCSS_POWER_REQUEST;
--
Jani Nikula, Intel
