> Subject: RE: [PATCH v2 04/24] drm/i915/lt_phy: Refactor LT PHY PLL handling
> to use explicit PLL state
>
> > -----Original Message-----
> > From: Deak, Imre <[email protected]>
> > Sent: Wednesday, 4 March 2026 16.05
> > To: Kahola, Mika <[email protected]>
> > Cc: [email protected]; [email protected]
> > Subject: Re: [PATCH v2 04/24] drm/i915/lt_phy: Refactor LT PHY PLL
> > handling to use explicit PLL state
> >
> > On Wed, Mar 04, 2026 at 01:14:03PM +0000, Mika Kahola wrote:
> > > The LT PHY implementation currently pulls PLL and port_clock
> > > information directly from the CRTC state. This ties the PHY
> > > programming logic too tightly to the CRTC state and makes it harder
> > > to clearly express the PHY’s own PLL configuration.
> > >
> > > Introduce an explicit "struct intel_lt_phy_pll_state" argument for
> > > the PHY functions and update callers accordingly.
> > >
> > > No functional change is intended — this is a preparatory cleanup for
> > > to bring LT PHY PLL handling as part of PLL framework.
> > >
> > > Signed-off-by: Mika Kahola <[email protected]>
> > > ---
> > > drivers/gpu/drm/i915/display/intel_lt_phy.c | 48
> > > ++++++++++++---------
> > > 1 file changed, 27 insertions(+), 21 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/display/intel_lt_phy.c
> > > b/drivers/gpu/drm/i915/display/intel_lt_phy.c
> > > index 8fe61cfdb706..ebdcab58df4a 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_lt_phy.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_lt_phy.c
> > > @@ -1178,7 +1178,8 @@ intel_lt_phy_lane_reset(struct intel_encoder
> > > *encoder,
> > >
> > > static void
> > > intel_lt_phy_program_port_clock_ctl(struct intel_encoder *encoder,
> > > - const struct intel_crtc_state *crtc_state,
> > > + const struct intel_lt_phy_pll_state *ltpll,
> > > + int port_clock,
> > > bool lane_reversal)
> > > {
> > > struct intel_display *display = to_intel_display(encoder); @@
> > > -1195,17 +1196,17 @@ intel_lt_phy_program_port_clock_ctl(struct
> intel_encoder *encoder,
> > > * but since the register bits still remain the same we use
> > > * the same definition
> > > */
> > > - if (intel_crtc_has_type(crtc_state, INTEL_OUTPUT_HDMI) &&
> > > - intel_hdmi_is_frl(crtc_state->port_clock))
> > > + if (encoder->type == INTEL_OUTPUT_HDMI &&
> >
> > This was discussed already elsewhere: encoder->type can't be used to
> > determine if the encoder is in HDMI or DP mode. In fact on LT PHY
> > platforms encoder->type will be never INTEL_OUTPUT_HDMI, rather it's
> INTEL_OUTPUT_DDI, where the actual mode of the DDI encoder could be
> either HDMI or DP.
> >
> > The ideal would be to deduct the DP/HDMI mode from the
> > intel_lt_phy_pll_state instead. AFAICS ltpll->config[0] is explicitly
> > set to
> > 0x84 for both the computed and table-specified HDMI PLL configurations
> and config[0] is not 0x84 for any DP PLL configurations.
> > Could be used that instead to distinguish the HDMI and DP configs?
>
> Right. I keep forgetting this that "encoder->type" can be both DP and HDMI.
> The naming to me seems a bit misleading and hence I keep forgetting this.
> Anyway, this approach cannot be used here but I must come up with better
> solution.
>
> I could switch to use config[0] to distinguish HDMI.
We could also use intel_encoder_is_dp() that makes sure we skip HDMI connectors
in that case.
Otherwise,
mode = REG_FIELD_GET8(LT_PHY_VDR_MODE_ENCODING_MASK, val);
mode & MODE_DP will also work
Regards,
Suraj Kandpal
>
> Thanks for a review!
>
> -Mika-
>
> >
> > > + intel_hdmi_is_frl(port_clock))
> > > val |= XELPDP_DDI_CLOCK_SELECT_PREP(display,
> XELPDP_DDI_CLOCK_SELECT_DIV18CLK);
> > > else
> > > val |= XELPDP_DDI_CLOCK_SELECT_PREP(display,
> > > XELPDP_DDI_CLOCK_SELECT_MAXPCLK);
> > >
> > > /* DP2.0 10G and 20G rates enable MPLLA*/
> > > - if (crtc_state->port_clock == 1000000 || crtc_state->port_clock ==
> 2000000)
> > > + if (port_clock == 1000000 || port_clock == 2000000)
> > > val |= XELPDP_SSC_ENABLE_PLLA;
> > > else
> > > - val |= crtc_state->dpll_hw_state.ltpll.ssc_enabled ?
> XELPDP_SSC_ENABLE_PLLB : 0;
> > > + val |= ltpll->ssc_enabled ? XELPDP_SSC_ENABLE_PLLB : 0;
> > >
> > > intel_de_rmw(display, XELPDP_PORT_CLOCK_CTL(display, encoder-
> >port),
> > > XELPDP_LANE1_PHY_CLOCK_SELECT |
> XELPDP_FORWARD_CLOCK_UNGATE
> > > | @@ -1248,10 +1249,12 @@ static u32 intel_lt_phy_get_dp_clock(u8
> > > rate)
> > >
> > > static bool
> > > intel_lt_phy_config_changed(struct intel_encoder *encoder,
> > > - const struct intel_crtc_state *crtc_state)
> > > + const struct intel_lt_phy_pll_state *ltpll)
> > > {
> > > + struct intel_display *display = to_intel_display(encoder);
> > > u8 val, rate;
> > > u32 clock;
> > > + u32 port_clock = intel_lt_phy_calc_port_clock(display, ltpll);
> > >
> > > val = intel_lt_phy_read(encoder, INTEL_LT_PHY_LANE0,
> > > LT_PHY_VDR_0_CONFIG);
> > > @@ -1262,9 +1265,10 @@ intel_lt_phy_config_changed(struct
> intel_encoder *encoder,
> > > * using 1.62 Gbps clock since PHY PLL defaults to that
> > > * otherwise we always need to reconfigure it.
> > > */
> > > - if (intel_crtc_has_dp_encoder(crtc_state)) {
> > > + if (encoder->type == INTEL_OUTPUT_DP ||
> > > + encoder->type == INTEL_OUTPUT_EDP) {
> >
> > Same as above, encoder->type can't be used here.
> >
> > > clock = intel_lt_phy_get_dp_clock(rate);
> > > - if (crtc_state->port_clock == 1620000 && crtc_state-
> >port_clock == clock)
> > > + if (port_clock == 1620000 && port_clock == clock)
> > > return false;
> > > }
> > >
> > > @@ -1759,41 +1763,41 @@ intel_lt_phy_pll_calc_state(struct
> > > intel_crtc_state *crtc_state,
> > >
> > > static void
> > > intel_lt_phy_program_pll(struct intel_encoder *encoder,
> > > - const struct intel_crtc_state *crtc_state)
> > > + const struct intel_lt_phy_pll_state *ltpll)
> > > {
> > > u8 owned_lane_mask =
> intel_lt_phy_get_owned_lane_mask(encoder);
> > > int i, j, k;
> > >
> > > intel_lt_phy_write(encoder, owned_lane_mask,
> LT_PHY_VDR_0_CONFIG,
> > > - crtc_state->dpll_hw_state.ltpll.config[0],
> MB_WRITE_COMMITTED);
> > > + ltpll->config[0], MB_WRITE_COMMITTED);
> > > intel_lt_phy_write(encoder, INTEL_LT_PHY_LANE0,
> LT_PHY_VDR_1_CONFIG,
> > > - crtc_state->dpll_hw_state.ltpll.config[1],
> MB_WRITE_COMMITTED);
> > > + ltpll->config[1], MB_WRITE_COMMITTED);
> > > intel_lt_phy_write(encoder, owned_lane_mask,
> LT_PHY_VDR_2_CONFIG,
> > > - crtc_state->dpll_hw_state.ltpll.config[2],
> MB_WRITE_COMMITTED);
> > > + ltpll->config[2], MB_WRITE_COMMITTED);
> > >
> > > for (i = 0; i <= 12; i++) {
> > > intel_lt_phy_write(encoder, INTEL_LT_PHY_LANE0,
> LT_PHY_VDR_X_ADDR_MSB(i),
> > > - crtc_state->dpll_hw_state.ltpll.addr_msb[i],
> > > + ltpll->addr_msb[i],
> > > MB_WRITE_COMMITTED);
> > > intel_lt_phy_write(encoder, INTEL_LT_PHY_LANE0,
> LT_PHY_VDR_X_ADDR_LSB(i),
> > > - crtc_state->dpll_hw_state.ltpll.addr_lsb[i],
> > > + ltpll->addr_lsb[i],
> > > MB_WRITE_COMMITTED);
> > >
> > > for (j = 3, k = 0; j >= 0; j--, k++)
> > > intel_lt_phy_write(encoder, INTEL_LT_PHY_LANE0,
> > > LT_PHY_VDR_X_DATAY(i, j),
> > > - crtc_state-
> >dpll_hw_state.ltpll.data[i][k],
> > > + ltpll->data[i][k],
> > > MB_WRITE_COMMITTED);
> > > }
> > > }
> > >
> > > static void
> > > intel_lt_phy_enable_disable_tx(struct intel_encoder *encoder,
> > > - const struct intel_crtc_state *crtc_state)
> > > + const struct intel_lt_phy_pll_state *ltpll,
> > > + u8 lane_count)
> > > {
> > > struct intel_digital_port *dig_port = enc_to_dig_port(encoder);
> > > bool lane_reversal = dig_port->lane_reversal;
> > > - u8 lane_count = crtc_state->lane_count;
> > > bool is_dp_alt =
> > > intel_tc_port_in_dp_alt_mode(dig_port);
> > > enum intel_tc_pin_assignment tc_pin = @@ -1895,7 +1899,8 @@
> void
> > > intel_lt_phy_pll_enable(struct intel_encoder *encoder,
> > > intel_lt_phy_lane_reset(encoder, crtc_state->lane_count);
> > >
> > > /* 2. Program PORT_CLOCK_CTL register to configure clock muxes,
> gating, and SSC. */
> > > - intel_lt_phy_program_port_clock_ctl(encoder, crtc_state,
> lane_reversal);
> > > + intel_lt_phy_program_port_clock_ctl(encoder, &crtc_state-
> >dpll_hw_state.ltpll,
> > > + crtc_state->port_clock,
> lane_reversal);
> > >
> > > /* 3. Change owned PHY lanes power to Ready state. */
> > > intel_lt_phy_powerdown_change_sequence(encoder,
> owned_lane_mask,
> > > @@
> > > -1905,12 +1910,12 @@ void intel_lt_phy_pll_enable(struct intel_encoder
> *encoder,
> > > * 4. Read the PHY message bus VDR register PHY_VDR_0_Config
> check enabled PLL type,
> > > * encoded rate and encoded mode.
> > > */
> > > - if (intel_lt_phy_config_changed(encoder, crtc_state)) {
> > > + if (intel_lt_phy_config_changed(encoder,
> > > +&crtc_state->dpll_hw_state.ltpll)) {
> > > /*
> > > * 5. Program the PHY internal PLL registers over PHY
> message bus for the desired
> > > * frequency and protocol type
> > > */
> > > - intel_lt_phy_program_pll(encoder, crtc_state);
> > > + intel_lt_phy_program_pll(encoder,
> > > +&crtc_state->dpll_hw_state.ltpll);
> > >
> > > /* 6. Use the P2P transaction flow */
> > > /*
> > > @@ -2001,7 +2006,8 @@ void intel_lt_phy_pll_enable(struct
> intel_encoder *encoder,
> > > intel_lt_phy_powerdown_change_sequence(encoder,
> owned_lane_mask,
> > > XELPDP_P0_STATE_ACTIVE);
> > >
> > > - intel_lt_phy_enable_disable_tx(encoder, crtc_state);
> > > + intel_lt_phy_enable_disable_tx(encoder, &crtc_state-
> >dpll_hw_state.ltpll,
> > > + crtc_state->lane_count);
> > > intel_lt_phy_transaction_end(encoder, wakeref); }
> > >
> > > --
> > > 2.43.0
> > >
