Re: [PATCH 12/12] drm/i915/xe3lpd: Power request asserting/deasserting

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 18 Oct 2024, Matt Atwood <matthew.s.atwood@intel.com> wrote:
> From: Mika Kahola <mika.kahola@intel.com>
>
> 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.
>
> Signed-off-by: Mika Kahola <mika.kahola@intel.com>
> Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_tc.c | 40 +++++++++++++++++++++++++
>  drivers/gpu/drm/i915/i915_reg.h         |  7 +++++
>  2 files changed, 47 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_tc.c b/drivers/gpu/drm/i915/display/intel_tc.c
> index 6f2ee7dbc43b..7d9f87db381c 100644
> --- a/drivers/gpu/drm/i915/display/intel_tc.c
> +++ b/drivers/gpu/drm/i915/display/intel_tc.c
> @@ -1013,6 +1013,39 @@ xelpdp_tc_phy_wait_for_tcss_power(struct intel_tc_port *tc, bool enabled)
>  	return true;
>  }
>  
> +static bool xelpdp_tc_phy_wait_for_tcss_ready(struct drm_i915_private *i915,

No new struct drm_i915_private params or variables please.

BR,
Jani.

> +					      bool enable)
> +{
> +	if (DISPLAY_VER(i915) < 30)
> +		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)) {
> +		drm_dbg_kms(&i915->drm,
> +			    "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_DATA(1));
> +
> +	/* 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,
> +			    "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 +1055,13 @@ 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,
> +		    !xelpdp_tc_phy_wait_for_tcss_ready(i915, enable));
> +
>  	val = intel_de_read(i915, reg);
>  	if (enable)
>  		val |= XELPDP_TCSS_POWER_REQUEST;
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 2743a2dd0a3d..d2775a32bf18 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -4539,6 +4539,13 @@ enum skl_power_gate {
>  #define  TCSS_DDI_STATUS_HPD_LIVE_STATUS_TBT	REG_BIT(1)
>  #define  TCSS_DDI_STATUS_HPD_LIVE_STATUS_ALT	REG_BIT(0)
>  
> +#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)
> +
>  #define PRIMARY_SPI_TRIGGER			_MMIO(0x102040)
>  #define PRIMARY_SPI_ADDRESS			_MMIO(0x102080)
>  #define PRIMARY_SPI_REGIONID			_MMIO(0x102084)

-- 
Jani Nikula, Intel