linux-kernel - Re: [PATCH] drm/i915/display: fix uninitialized variable

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Date:   Sat, 29 Aug 2020 01:10:51 +0000
From:   "Souza, Jose" <jose.souza@...el.com>
To:     "airlied@...ux.ie" <airlied@...ux.ie>,
        "Vivi, Rodrigo" <rodrigo.vivi@...el.com>,
        "Roper, Matthew D" <matthew.d.roper@...el.com>,
        "joonas.lahtinen@...ux.intel.com" <joonas.lahtinen@...ux.intel.com>,
        "Srivatsa, Anusha" <anusha.srivatsa@...el.com>,
        "Laxminarayan Bharadiya, Pankaj" 
        <pankaj.laxminarayan.bharadiya@...el.com>,
        "trix@...hat.com" <trix@...hat.com>,
        "wambui.karugax@...il.com" <wambui.karugax@...il.com>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "jani.nikula@...ux.intel.com" <jani.nikula@...ux.intel.com>,
        "Kasireddy, Vivek" <vivek.kasireddy@...el.com>
CC:     "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/i915/display: fix uninitialized variable

Just merged the first patch that fixed this issue, thanks anyways.

2034c2129bc4a91d471815d4dc7a2a69eaa5338d - drm/i915/display: Ensure that ret is always initialized in icl_combo_phy_verify_state


On Tue, 2020-08-25 at 16:20 -0700, trix@...hat.com wrote:
> From: Tom Rix <
> trix@...hat.com
> >
> 
> clang static analysis flags this error
> 
> intel_combo_phy.c:268:7: warning: The left expression of the
>   compound assignment is an uninitialized value.
>   The computed value will also be garbage
>                 ret &= check_phy_reg(...
>                 ~~~ ^
> 
> ret has no initial values, in icl_combo_phy_verify_state() ret is
> set by the next statment and then updated by similar &= logic.
> 
> Because the check_phy_req() are only register reads, reorder the
> statements.
> 
> Fixes: 239bef676d8e ("drm/i915/display: Implement new combo phy initialization step")
> Signed-off-by: Tom Rix <
> trix@...hat.com
> >
> ---
>  drivers/gpu/drm/i915/display/intel_combo_phy.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_combo_phy.c b/drivers/gpu/drm/i915/display/intel_combo_phy.c
> index 6968de4f3477..7622ef66c987 100644
> --- a/drivers/gpu/drm/i915/display/intel_combo_phy.c
> +++ b/drivers/gpu/drm/i915/display/intel_combo_phy.c
> @@ -264,6 +264,8 @@ static bool icl_combo_phy_verify_state(struct drm_i915_private *dev_priv,
>  	if (!icl_combo_phy_enabled(dev_priv, phy))
>  		return false;
>  
> +	ret = cnl_verify_procmon_ref_values(dev_priv, phy);
> +
>  	if (INTEL_GEN(dev_priv) >= 12) {
>  		ret &= check_phy_reg(dev_priv, phy, ICL_PORT_TX_DW8_LN0(phy),
>  				     ICL_PORT_TX_DW8_ODCC_CLK_SEL |
> @@ -276,8 +278,6 @@ static bool icl_combo_phy_verify_state(struct drm_i915_private *dev_priv,
>  				     DCC_MODE_SELECT_CONTINUOSLY);
>  	}
>  
> -	ret = cnl_verify_procmon_ref_values(dev_priv, phy);
> -
>  	if (phy_is_master(dev_priv, phy)) {
>  		ret &= check_phy_reg(dev_priv, phy, ICL_PORT_COMP_DW8(phy),
>  				     IREFGEN, IREFGEN);
>