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

[Kahola, Mika]

> -----Original Message-----
> From: Jani Nikula <jani.nikula at linux.intel.com>
> Sent: Monday, 28 October 2024 16.55
> To: Kahola, Mika <mika.kahola at intel.com>; intel-gfx at lists.freedesktop.org
> Cc: Sousa, Gustavo <gustavo.sousa at intel.com>; Kahola, Mika
> <mika.kahola at intel.com>
> Subject: Re: [PATCH] drm/i915/xe3lpd: Power request asserting/deasserting
> 
> On Mon, 28 Oct 2024, Mika Kahola <mika.kahola at intel.com> 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 at intel.com>
> > ---
> >  .../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.

Ok I will switch to use that. Thanks!

> 
> > +					 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