Re: [PATCH v6 13/18] drm/i915/alpm: Enable MAC Transmitting LFPS for LT PHY

["Hogander, Jouni" <jouni.hogander@intel.com>]

On Tue, 2026-09-15 at 23:34 +0530, Animesh Manna wrote:
> Enable MAC to transmit LFPS via LT PHY during aux-less alpm.
> 
> v2:
> - Correct commit description. [Suraj]
> - Remove loop as no dependency on the transmitter LT_PHY_CMN_CTL0.
> [Suraj]
> v3: Cosmetic changes. [Suraj]
> 
Bspec reference.

> Cc: Jouni Högander <jouni.hogander@intel.com>
> Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
> Signed-off-by: Animesh Manna <animesh.manna@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c      |  5 +++-
>  drivers/gpu/drm/i915/display/intel_lt_phy.c   | 27
> +++++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_lt_phy.h   |  2 ++
>  .../gpu/drm/i915/display/intel_lt_phy_regs.h  |  3 +++
>  4 files changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c
> b/drivers/gpu/drm/i915/display/intel_ddi.c
> index 9b3b526e5e55..5244218132aa 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -3796,7 +3796,10 @@ static void
> mtl_ddi_prepare_link_retrain(struct intel_dp *intel_dp,
>  	 *     ii. Enable MAC Transmits LFPS in the "PHY Common
> Control 0" PIPE
>  	 *         register
>  	 */
> -	intel_lnl_mac_transmit_lfps(encoder, crtc_state);
> +	if (HAS_LT_PHY(display))
> +		intel_xe3plpd_mac_transmit_lfps(encoder,
> crtc_state);

Maybe better prefix for this would be intel_lt_mac_*

> +	else
> +		intel_lnl_mac_transmit_lfps(encoder, crtc_state);
>  }
>  
>  static void intel_ddi_prepare_link_retrain(struct intel_dp
> *intel_dp,
> diff --git a/drivers/gpu/drm/i915/display/intel_lt_phy.c
> b/drivers/gpu/drm/i915/display/intel_lt_phy.c
> index 86492651b01d..4fe010df20be 100644
> --- a/drivers/gpu/drm/i915/display/intel_lt_phy.c
> +++ b/drivers/gpu/drm/i915/display/intel_lt_phy.c
> @@ -5,6 +5,7 @@
>  
>  #include <drm/drm_print.h>
>  
> +#include "intel_alpm.h"
>  #include "intel_cx0_phy.h"
>  #include "intel_cx0_phy_regs.h"
>  #include "intel_ddi.h"
> @@ -2357,3 +2358,29 @@ void intel_lt_phy_verify_plls(struct
> intel_display *display)
>  	intel_lt_phy_pll_verify_tables(display,
> xe3plpd_lt_edp_tables);
>  	intel_lt_phy_pll_verify_tables(display,
> xe3plpd_lt_hdmi_tables);
>  }
> +
> +/*
> + * According to HAS we need to enable MAC Transmitting LFPS in the
> "PHY Common
> + * Control 0" PIPE register in case of AUX Less ALPM is going to be
> used. This
> + * function is doing that and is called by link retrain sequence.
> + */
> +void intel_xe3plpd_mac_transmit_lfps(struct intel_encoder *encoder,
> +				     const struct intel_crtc_state
> *crtc_state)
> +{
> +	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> +	struct ref_tracker *wakeref;
> +	u8 owned_lane_mask;
> +
> +	if (!intel_alpm_is_alpm_aux_less(intel_dp, crtc_state))
> +		return;

You should also check alpm or modify intel_alpm_is_alpm_aux_less.

> +
> +	wakeref = intel_lt_phy_transaction_begin(encoder);
> +
> +	owned_lane_mask = intel_lt_phy_get_owned_lane_mask(encoder);
> +
> +	intel_lt_phy_rmw(encoder, owned_lane_mask, LT_PHY_CMN_CTL_0,
> +			 LT_PHY_CMN_LFPS_ENABLE,
> +			 LT_PHY_CMN_LFPS_ENABLE,
> MB_WRITE_COMMITTED);
> +
> +	intel_lt_phy_transaction_end(encoder, wakeref);
> +}
> diff --git a/drivers/gpu/drm/i915/display/intel_lt_phy.h
> b/drivers/gpu/drm/i915/display/intel_lt_phy.h
> index 16de39484779..c76c97b90946 100644
> --- a/drivers/gpu/drm/i915/display/intel_lt_phy.h
> +++ b/drivers/gpu/drm/i915/display/intel_lt_phy.h
> @@ -49,5 +49,7 @@ void intel_xe3plpd_pll_enable(struct intel_encoder
> *encoder,
>  			      const struct intel_dpll_hw_state
> *dpll_hw_state);
>  void intel_xe3plpd_pll_disable(struct intel_encoder *encoder);
>  void intel_lt_phy_verify_plls(struct intel_display *display);
> +void intel_xe3plpd_mac_transmit_lfps(struct intel_encoder *encoder,
> +				     const struct intel_crtc_state
> *crtc_state);
>  
>  #endif /* __INTEL_LT_PHY_H__ */
> diff --git a/drivers/gpu/drm/i915/display/intel_lt_phy_regs.h
> b/drivers/gpu/drm/i915/display/intel_lt_phy_regs.h
> index ff6d7829dbb9..b64ff57e0c09 100644
> --- a/drivers/gpu/drm/i915/display/intel_lt_phy_regs.h
> +++ b/drivers/gpu/drm/i915/display/intel_lt_phy_regs.h
> @@ -35,6 +35,9 @@
>  #define LT_PHY_TXY_CTL10_MAC(idx)	_MMIO(LT_PHY_TXY_CTL10(idx))
>  #define  LT_PHY_TX_LANE_ENABLE		REG_BIT8(0)
>  
> +#define LT_PHY_CMN_CTL_0		(0x800)
> +#define  LT_PHY_CMN_LFPS_ENABLE		REG_BIT8(1)

LT_PHY_CMN_MAC_TRANSMIT_LFPS would better follow what is in Bspec.

BR,
Jouni Högander

> +
>  /* LT Phy Vendor Register */
>  #define LT_PHY_VDR_0_CONFIG	0xC02
>  #define  LT_PHY_VDR_DP_PLL_ENABLE	REG_BIT(7)