> -----Original Message-----
> From: Nikula, Jani <jani.nik...@intel.com>
> Sent: Tuesday, February 11, 2025 10:27 PM
> To: Kandpal, Suraj <suraj.kand...@intel.com>; intel-
> x...@lists.freedesktop.org; intel-gfx@lists.freedesktop.org
> Cc: Nautiyal, Ankit K <ankit.k.nauti...@intel.com>
> Subject: RE: [PATCH 8/9] drm/i915/dpll: Accept intel_display as argument for
> shared_dpll_init
>
> On Tue, 11 Feb 2025, "Kandpal, Suraj" <suraj.kand...@intel.com> wrote:
> >> -----Original Message-----
> >> From: Nikula, Jani <jani.nik...@intel.com>
> >> Sent: Tuesday, February 11, 2025 6:45 PM
> >> To: Kandpal, Suraj <suraj.kand...@intel.com>; intel-
> >> x...@lists.freedesktop.org; intel-gfx@lists.freedesktop.org
> >> Cc: Nautiyal, Ankit K <ankit.k.nauti...@intel.com>; Kandpal, Suraj
> >> <suraj.kand...@intel.com>
> >> Subject: Re: [PATCH 8/9] drm/i915/dpll: Accept intel_display as
> >> argument for shared_dpll_init
> >>
> >> On Tue, 11 Feb 2025, Suraj Kandpal <suraj.kand...@intel.com> wrote:
> >> > Use intel_display as an argument for intel_shared_dpll_init() and
> >> > replace drm_i915_private in function wherever possible.
> >> > While at it prefer using display->platform.xx over IS_PLATFORM.
> >> >
> >> > Signed-off-by: Suraj Kandpal <suraj.kand...@intel.com>
> >> > ---
> >> > .../drm/i915/display/intel_display_driver.c | 2 +-
> >> > drivers/gpu/drm/i915/display/intel_dpll_mgr.c | 49
> >> > ++++++++++--------- drivers/gpu/drm/i915/display/intel_dpll_mgr.h
> >> > ++++++++++|
> >> > 3 +-
> >> > 3 files changed, 27 insertions(+), 27 deletions(-)
> >> >
> >> > diff --git a/drivers/gpu/drm/i915/display/intel_display_driver.c
> >> > b/drivers/gpu/drm/i915/display/intel_display_driver.c
> >> > index 978f530c810e..852f1129a058 100644
> >> > --- a/drivers/gpu/drm/i915/display/intel_display_driver.c
> >> > +++ b/drivers/gpu/drm/i915/display/intel_display_driver.c
> >> > @@ -448,7 +448,7 @@ int intel_display_driver_probe_nogem(struct
> >> intel_display *display)
> >> > }
> >> >
> >> > intel_plane_possible_crtcs_init(display);
> >> > - intel_shared_dpll_init(i915);
> >> > + intel_shared_dpll_init(display);
> >> > intel_fdi_pll_freq_update(i915);
> >> >
> >> > intel_update_czclk(i915);
> >> > diff --git a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
> >> > b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
> >> > index f94da1ffc8ce..26b6b9372fa3 100644
> >> > --- a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
> >> > +++ b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
> >> > @@ -2042,8 +2042,8 @@ static void bxt_ddi_pll_enable(struct
> >> > intel_display *display, {
> >> > const struct bxt_dpll_hw_state *hw_state = &dpll_hw_state->bxt;
> >> > enum port port = (enum port)pll->info->id; /* 1:1 port->PLL
> >> > mapping
> >> */
> >> > - enum dpio_phy phy;
> >> > - enum dpio_channel ch;
> >> > + enum dpio_phy phy = DPIO_PHY0;
> >> > + enum dpio_channel ch = DPIO_CH0;
> >>
> >> Unrelated change, please drop.
> >>
> >
> > The problem is by dropping these changes I am not able to build the
> > kernel and it throws the following warning because of which I had to
> > add this
> >
> >
> > drivers/gpu/drm/i915/display/intel_dpll_mgr.c: In function
> _bxt_ddi_pll_enable_:
> > ./drivers/gpu/drm/xe/compat-i915-headers/../../i915/i915_reg_defs.h:24
> > 0:56: error: _phy_ is used uninitialized [-Werror=uniniti alized]
> > 240 | (BUILD_BUG_ON_ZERO(!__is_constexpr(__c_index)) +
> \
> > | ^
> > drivers/gpu/drm/i915/display/intel_dpll_mgr.c:2047:23: note: _phy_ was
> declared here
> > 2047 | enum dpio_phy phy;
> > | ^~~
> > In file included from ./drivers/gpu/drm/xe/compat-i915-
> headers/i915_reg_defs.h:6,
> > from
> > drivers/gpu/drm/i915/display/intel_display_reg_defs.h:9,
> > from drivers/gpu/drm/i915/display/bxt_dpio_phy_regs.h:9,
> > from drivers/gpu/drm/i915/display/intel_dpll_mgr.c:27:
> > ./drivers/gpu/drm/xe/compat-i915-headers/../../i915/i915_reg_defs.h:21
> > 3:58: error: _ch_ is used uninitialized [-Werror=uninitia lized]
> > 213 | #define _PICK_EVEN(__index, __a, __b) ((__a) + (__index) * ((__b) -
> (__a)))
> > | ^
> > drivers/gpu/drm/i915/display/intel_dpll_mgr.c:2048:27: note: _ch_ was
> declared here
> > 2048 | enum dpio_channel ch;
>
> Did you think to look into why this happens? I encourage you to always do
> that instead of just silencing the warning. You'll learn about C and the
> compiler.
>
> It's quite interesting and subtle and deserves to be mentioned in the
> commit message.
>
> For i915.ko, bxt_port_to_phy_channel() is a regular function, and the
> compiler will likely assume it'll initialize the parameters. And it does.
>
> For xe.ko, bxt_port_to_phy_channel() is a static inline stub, and the
> compiler can be absolutely certain the parameters aren't initialized.
>
> So, why does this cause an error now? The above didn't change now!
>
> With IS_GEMINILAKE() || IS_BROXTON() the compiler can be sure it's false
> for xe.ko. The whole chain bxt_pll_mgr -> bxt_plls -> bxt_ddi_pll_funcs
> -> bxt_ddi_pll_enable can be optimized away. It's unreachable.
>
> Not so with display->platform.geminilake ||
> display->platform.broxton. The compiler sees use of uninitialized
> variables.
Ahh ohkay, I understand it now thanks for explaining it.
Will amend the commit message
Will explore these things and add them to commit message in future too.
Regards,
Suraj Kandpal
>
> BR,
> Jani.
>
>
>
> >
> > Regards,
> > Suraj Kandpal
> >
> >> With that fixed,
> >>
> >> Reviewed-by: Jani Nikula <jani.nik...@intel.com>
> >>
> >>
> >> > u32 temp;
> >> >
> >> > bxt_port_to_phy_channel(display, port, &phy, &ch); @@ -4302,40
> >> > +4302,41 @@ static const struct intel_dpll_mgr adlp_pll_mgr = {
> >> >
> >> > /**
> >> > * intel_shared_dpll_init - Initialize shared DPLLs
> >> > - * @i915: i915 device
> >> > + * @display: intel_display device
> >> > *
> >> > - * Initialize shared DPLLs for @i915.
> >> > + * Initialize shared DPLLs for @display.
> >> > */
> >> > -void intel_shared_dpll_init(struct drm_i915_private *i915)
> >> > +void intel_shared_dpll_init(struct intel_display *display)
> >> > {
> >> > + struct drm_i915_private *i915 = to_i915(display->drm);
> >> > const struct intel_dpll_mgr *dpll_mgr = NULL;
> >> > const struct dpll_info *dpll_info;
> >> > int i;
> >> >
> >> > - mutex_init(&i915->display.dpll.lock);
> >> > + mutex_init(&display->dpll.lock);
> >> >
> >> > - if (DISPLAY_VER(i915) >= 14 || IS_DG2(i915))
> >> > + if (DISPLAY_VER(display) >= 14 || display->platform.dg2)
> >> > /* No shared DPLLs on DG2; port PLLs are part of the PHY */
> >> > dpll_mgr = NULL;
> >> > - else if (IS_ALDERLAKE_P(i915))
> >> > + else if (display->platform.alderlake_p)
> >> > dpll_mgr = &adlp_pll_mgr;
> >> > - else if (IS_ALDERLAKE_S(i915))
> >> > + else if (display->platform.alderlake_s)
> >> > dpll_mgr = &adls_pll_mgr;
> >> > - else if (IS_DG1(i915))
> >> > + else if (display->platform.dg1)
> >> > dpll_mgr = &dg1_pll_mgr;
> >> > - else if (IS_ROCKETLAKE(i915))
> >> > + else if (display->platform.rocketlake)
> >> > dpll_mgr = &rkl_pll_mgr;
> >> > - else if (DISPLAY_VER(i915) >= 12)
> >> > + else if (DISPLAY_VER(display) >= 12)
> >> > dpll_mgr = &tgl_pll_mgr;
> >> > - else if (IS_JASPERLAKE(i915) || IS_ELKHARTLAKE(i915))
> >> > + else if (display->platform.jasperlake ||
> >> > +display->platform.elkhartlake)
> >> > dpll_mgr = &ehl_pll_mgr;
> >> > - else if (DISPLAY_VER(i915) >= 11)
> >> > + else if (DISPLAY_VER(display) >= 11)
> >> > dpll_mgr = &icl_pll_mgr;
> >> > - else if (IS_GEMINILAKE(i915) || IS_BROXTON(i915))
> >> > + else if (display->platform.geminilake ||
> >> > + display->platform.broxton)
> >> > dpll_mgr = &bxt_pll_mgr;
> >> > - else if (DISPLAY_VER(i915) == 9)
> >> > + else if (DISPLAY_VER(display) == 9)
> >> > dpll_mgr = &skl_pll_mgr;
> >> > - else if (HAS_DDI(i915))
> >> > + else if (HAS_DDI(display))
> >> > dpll_mgr = &hsw_pll_mgr;
> >> > else if (HAS_PCH_IBX(i915) || HAS_PCH_CPT(i915))
> >> > dpll_mgr = &pch_pll_mgr; @@ -4346,20 +4347,20 @@ void
> >> > intel_shared_dpll_init(struct
> >> drm_i915_private *i915)
> >> > dpll_info = dpll_mgr->dpll_info;
> >> >
> >> > for (i = 0; dpll_info[i].name; i++) {
> >> > - if (drm_WARN_ON(&i915->drm,
> >> > - i >= ARRAY_SIZE(i915-
> >> >display.dpll.shared_dplls)))
> >> > + if (drm_WARN_ON(display->drm,
> >> > + i >=
> >> > + ARRAY_SIZE(display->dpll.shared_dplls)))
> >> > break;
> >> >
> >> > /* must fit into unsigned long bitmask on 32bit */
> >> > - if (drm_WARN_ON(&i915->drm, dpll_info[i].id >= 32))
> >> > + if (drm_WARN_ON(display->drm, dpll_info[i].id >= 32))
> >> > break;
> >> >
> >> > - i915->display.dpll.shared_dplls[i].info = &dpll_info[i];
> >> > - i915->display.dpll.shared_dplls[i].index = i;
> >> > + display->dpll.shared_dplls[i].info = &dpll_info[i];
> >> > + display->dpll.shared_dplls[i].index = i;
> >> > }
> >> >
> >> > - i915->display.dpll.mgr = dpll_mgr;
> >> > - i915->display.dpll.num_shared_dpll = i;
> >> > + display->dpll.mgr = dpll_mgr;
> >> > + display->dpll.num_shared_dpll = i;
> >> > }
> >> >
> >> > /**
> >> > diff --git a/drivers/gpu/drm/i915/display/intel_dpll_mgr.h
> >> > b/drivers/gpu/drm/i915/display/intel_dpll_mgr.h
> >> > index 3d988f17f31d..caffb084830c 100644
> >> > --- a/drivers/gpu/drm/i915/display/intel_dpll_mgr.h
> >> > +++ b/drivers/gpu/drm/i915/display/intel_dpll_mgr.h
> >> > @@ -35,7 +35,6 @@
> >> > ((__pll) = &(__display)->dpll.shared_dplls[(__i)])
> >> > ; (__i)++)
> >> >
> >> > enum tc_port;
> >> > -struct drm_i915_private;
> >> > struct drm_printer;
> >> > struct intel_atomic_state;
> >> > struct intel_crtc;
> >> > @@ -422,7 +421,7 @@ bool intel_dpll_get_hw_state(struct
> >> > intel_display *display, void intel_enable_shared_dpll(const struct
> >> > intel_crtc_state *crtc_state); void
> >> > intel_disable_shared_dpll(const struct intel_crtc_state
> >> > *crtc_state); void intel_shared_dpll_swap_state(struct
> >> > intel_atomic_state *state); -void intel_shared_dpll_init(struct
> >> > drm_i915_private *i915);
> >> > +void intel_shared_dpll_init(struct intel_display *display);
> >> > void intel_dpll_update_ref_clks(struct intel_display *display);
> >> > void intel_dpll_readout_hw_state(struct intel_display *display);
> >> > void intel_dpll_sanitize_state(struct intel_display *display);
> >>
> >> --
> >> Jani Nikula, Intel
>
> --
> Jani Nikula, Intel
