Re: [PATCH v3 1/2] drm/i915/xe3lpd: Power request asserting/deasserting

[Raag Jadav <raag.jadav@intel.com>]

On Thu, Oct 31, 2024 at 01:40:26PM +0200, Mika Kahola 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)
> 
> Signed-off-by: Mika Kahola <mika.kahola@intel.com>
> ---
>  .../gpu/drm/i915/display/intel_cx0_phy_regs.h |  8 +++++
>  drivers/gpu/drm/i915/display/intel_tc.c       | 32 +++++++++++++++++++
>  2 files changed, 40 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 | \
> +						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..dab2ac7ec0dd 100644
> --- a/drivers/gpu/drm/i915/display/intel_tc.c
> +++ b/drivers/gpu/drm/i915/display/intel_tc.c
> @@ -1013,6 +1013,31 @@ 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)

Can be one line?

Raag