> -----Original Message-----
> From: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> Sent: Tuesday, 26 November 2024 11.30
> To: Kahola, Mika <mika.kahola@xxxxxxxxx>; intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: Sousa, Gustavo <gustavo.sousa@xxxxxxxxx>; Jadav, Raag
> <raag.jadav@xxxxxxxxx>; Kahola, Mika <mika.kahola@xxxxxxxxx>
> Subject: Re: [PATCH v5 1/2] drm/i915/xe3lpd: Power request
> asserting/deasserting
>
> On Tue, 05 Nov 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)
> > v3: Use "struct intel_display" instead of "struct drm_i915_private" (Jani)
> > Move defs above C10 definitions in the
> > intel_cx0_phy_regs.h file (Gustavo)
> > Move drm_WARN_ON() inside WA function (Gustavo)
> > Rename workaround function as wa_14020908590() (Gustvo)
> > Use boolean enable instead of if-else structure (Raag)
> > v4: Drop drm_WARN_ON() (Raag)
> > Fix function definition to fit into a single line (Raag)
> >
> > Reviewed-by: Raag Jadav <raag.jadav@xxxxxxxxx>
> > Signed-off-by: Mika Kahola <mika.kahola@xxxxxxxxx>
> > ---
> > .../gpu/drm/i915/display/intel_cx0_phy_regs.h | 8 +++++
> > drivers/gpu/drm/i915/display/intel_tc.c | 31 +++++++++++++++++++
> > 2 files changed, 39 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 f0e5c196eae4..5a0b55cca4a3 100644
> > --- a/drivers/gpu/drm/i915/display/intel_cx0_phy_regs.h
> > +++ b/drivers/gpu/drm/i915/display/intel_cx0_phy_regs.h
> > @@ -200,6 +200,14 @@
> > #define XELPDP_SSC_ENABLE_PLLA REG_BIT(1)
> > #define XELPDP_SSC_ENABLE_PLLB 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(val)
> (TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY | \
>
> Why does this contain TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY? You set it
> separately anyway (and that's how it should be).
This is a leftover. The suggestion was to use these separately and not combine these. Simply forgot to remove this from here.
>
> > +
> REG_FIELD_PREP(TCSS_DISP_MAILBOX_IN_CMD_CMD_MASK, val))
> > +
> > +#define TCSS_DISP_MAILBOX_IN_DATA _MMIO(0x161304)
> > +
> > /* C10 Vendor Registers */
> > #define PHY_C10_VDR_PLL(idx) (0xC00 + (idx))
> > #define C10_PLL0_FRACEN REG_BIT8(4)
> > diff --git a/drivers/gpu/drm/i915/display/intel_tc.c
> > b/drivers/gpu/drm/i915/display/intel_tc.c
> > index b16c4d2d4077..e40d55f4c0c4 100644
> > --- a/drivers/gpu/drm/i915/display/intel_tc.c
> > +++ b/drivers/gpu/drm/i915/display/intel_tc.c
> > @@ -1013,6 +1013,30 @@ xelpdp_tc_phy_wait_for_tcss_power(struct
> intel_tc_port *tc, bool enabled)
> > return true;
> > }
> >
> > +static void wa_14020908590(struct intel_display *display, bool
> > +enable)
>
> Yeah I still don't like functions named wa_14020908590. It's meaningless. What
> does it do?
That's a good point. We do have few functions in our driver that have workaround number in its name.
What would be the better way? Add a comment that references to workaround number and have a meaningful function name?
>
> > +{
> > + /* check if mailbox is running busy */
> > + if (intel_de_wait_for_clear(display, TCSS_DISP_MAILBOX_IN_CMD,
> > + TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY,
> 10)) {
> > + drm_dbg_kms(display->drm,
> > + "Timeout waiting for TCSS mailbox run/busy bit to
> clear\n");
> > + return;
> > + }
> > +
> > + intel_de_write(display, TCSS_DISP_MAILBOX_IN_DATA, enable);
>
> Not a fan of bool -> u32 implicit conversion here, with the register contents not
> described.
Ok. I will modify this to use u32 instead.
>
> > + intel_de_write(display, 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(display, TCSS_DISP_MAILBOX_IN_CMD,
> > + TCSS_DISP_MAILBOX_IN_CMD_RUN_BUSY,
> 10)) {
> > + drm_dbg_kms(display->drm,
> > + "Timeout after writing data to mailbox. Mailbox
> run/busy bit did not clear\n");
> > + return;
> > + }
> > +}
> > +
> > 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 +1046,13
> > @@ static void __xelpdp_tc_phy_enable_tcss_power(struct intel_tc_port
> > *tc, bool ena
> >
> > assert_tc_cold_blocked(tc);
> >
> > + /*
> > + * Gfx driver WA 14020908590 for PTL tcss_rxdetect_clkswb_req/ack
> > + * handshake violation when pwwreq= 0->1 during TC7/10 entry
> > + */
> > + if (DISPLAY_VER(i915) == 30)
> > + wa_14020908590(&i915->display, enable);
>
> You should add
>
> struct intel_display *display = &i915->display;
>
> local variable already in this patch, so the next patch doesn't have to modify the
> above line again. You can do the subsequent conversions in the follow-up.
Ok. I will make this change
Thanks for the review!
-Mika-
>
> BR,
> Jani.
>
>
> > +
> > val = intel_de_read(i915, reg);
> > if (enable)
> > val |= XELPDP_TCSS_POWER_REQUEST;
>
> --
> Jani Nikula, Intel
