[PATCH] drm/amd/display: use proper context for logging

[PATCH] drm/amd/display: use proper context for logging

[Jiri Slaby (SUSE)]

The same as the rest of the code, get_ss_info_from_atombios() uses
calc_pll_cs->ctx->logger for logging. But calc_pll_cs->ctx is
initialized only later in calc_pll_max_vco_construct(). Therefore, any
output using DC_LOG_SYNC() leads to a NULL pointer deference in
get_ss_info_from_atombios().

To avoid accessing the NULL context, use clk_src->base.ctx->logger
in get_ss_info_from_atombios(). That context is initialized earlier in
dce110_clk_src_construct() -- before get_ss_info_from_atombios() is
actually called. This is done by temporarily redefining DC_LOGGER to
CTX->logger.

Before:
dce110_clk_src_construct() did:
 -> sets clk_src->base.ctx = ctx;
 -> ss_info_from_atombios_create()
   -> get_ss_info_from_atombios()   <- uses calc_pll_cs->ctx  # BOOM
 -> calc_pll_max_vco_construct()    <- sets calc_pll_cs->ctx

After:
dce110_clk_src_construct() does:
 -> sets clk_src->base.ctx = ctx;
 -> ss_info_from_atombios_create()
   -> get_ss_info_from_atombios()   <- uses clk_src->base.ctx

Closes: https://bugzilla.suse.com/show_bug.cgi?id=1271175
Closes: https://lore.kernel.org/all/a9ee54e6-2413-4156-9bde-d528ae3c63a3@kernel.org/
Fixes: 1296423bf23c ("drm/amd/display: define DC_LOGGER for logger")
Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: Lakha, Bhawanpreet <Bhawanpreet.Lakha@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Rodrigo Siqueira <siqueira@igalia.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: amd-gfx@lists.freedesktop.org
---
Cc: dri-devel@lists.freedesktop.org
---
 drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c b/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
index ecb8493ec523..d3f7aa853e3a 100644
--- a/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
@@ -1513,6 +1513,10 @@ static const struct clock_source_funcs dce110_clk_src_funcs = {
 	.get_dp_dto_frequency_100hz = get_dp_dto_frequency_100hz
 };
 
+/* calc_pll_cs->ctx is set only after get_ss_info_from_atombios(), unlike clk_src->base */
+#pragma push_macro("DC_LOGGER")
+#undef DC_LOGGER
+#define DC_LOGGER CTX->logger
 
 static void get_ss_info_from_atombios(
 		struct dce110_clk_src *clk_src,
@@ -1526,7 +1530,7 @@ static void get_ss_info_from_atombios(
 	struct spread_spectrum_info *ss_info_cur;
 	struct spread_spectrum_data *ss_data_cur;
 	uint32_t i;
-	DC_LOGGER_INIT();
+
 	if (ss_entries_num == NULL) {
 		DC_LOG_SYNC(
 			"Invalid entry !!!\n");
@@ -1631,6 +1635,8 @@ static void get_ss_info_from_atombios(
 	kfree(ss_info);
 }
 
+#pragma pop_macro("DC_LOGGER")
+
 static void ss_info_from_atombios_create(
 	struct dce110_clk_src *clk_src)
 {
-- 
2.55.0

Re: [PATCH] drm/amd/display: use proper context for logging

[Lakha, Bhawanpreet]

Hey, why not just do 

--- a/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
@@ -45,7 +45,7 @@
        clk_src->base.ctx

 #define DC_LOGGER \
-       calc_pll_cs->ctx->logger
+       clk_src->base.ctx->logger or CTX->logger


clk_src is available everywhere right after dce110_clk_src_construct()


Bhawan


________________________________________
From: Lakha, Bhawanpreet <Bhawanpreet.Lakha@amd.com>
Sent: July 22, 2026 1:51 PM
To: Jiri Slaby (SUSE) <jirislaby@kernel.org>; Deucher, Alexander <Alexander.Deucher@amd.com>
Cc: linux-kernel@vger.kernel.org <linux-kernel@vger.kernel.org>; Wentland, Harry <Harry.Wentland@amd.com>; Li, Sun peng (Leo) <Sunpeng.Li@amd.com>; Rodrigo Siqueira <siqueira@igalia.com>; Koenig, Christian <Christian.Koenig@amd.com>; David Airlie <airlied@gmail.com>; Simona Vetter <simona@ffwll.ch>; amd-gfx@lists.freedesktop.org <amd-gfx@lists.freedesktop.org>; dri-devel@lists.freedesktop.org <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH] drm/amd/display: use proper context for logging
 
AMD General

Why not just do 

--- a/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
@@ -45,7 +45,7 @@
        clk_src->base.ctx

 #define DC_LOGGER \
-       calc_pll_cs->ctx->logger
+       clk_src->base.ctx->logger or CTX->logger


clk_src is available everywhere right after dce110_clk_src_construct()


Bhawan

________________________________________
From: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Sent: July 22, 2026 2:32 AM
To: Deucher, Alexander <Alexander.Deucher@amd.com>
Cc: linux-kernel@vger.kernel.org <linux-kernel@vger.kernel.org>; Jiri Slaby (SUSE) <jirislaby@kernel.org>; Lakha, Bhawanpreet <Bhawanpreet.Lakha@amd.com>; Wentland, Harry <Harry.Wentland@amd.com>; Li, Sun peng (Leo) <Sunpeng.Li@amd.com>; Rodrigo Siqueira <siqueira@igalia.com>; Koenig, Christian <Christian.Koenig@amd.com>; David Airlie <airlied@gmail.com>; Simona Vetter <simona@ffwll.ch>; amd-gfx@lists.freedesktop.org <amd-gfx@lists.freedesktop.org>; dri-devel@lists.freedesktop.org <dri-devel@lists.freedesktop.org>
Subject: [PATCH] drm/amd/display: use proper context for logging
 
The same as the rest of the code, get_ss_info_from_atombios() uses
calc_pll_cs->ctx->logger for logging. But calc_pll_cs->ctx is
initialized only later in calc_pll_max_vco_construct(). Therefore, any
output using DC_LOG_SYNC() leads to a NULL pointer deference in
get_ss_info_from_atombios().

To avoid accessing the NULL context, use clk_src->base.ctx->logger
in get_ss_info_from_atombios(). That context is initialized earlier in
dce110_clk_src_construct() -- before get_ss_info_from_atombios() is
actually called. This is done by temporarily redefining DC_LOGGER to
CTX->logger.

Before:
dce110_clk_src_construct() did:
 -> sets clk_src->base.ctx = ctx;
 -> ss_info_from_atombios_create()
   -> get_ss_info_from_atombios()   <- uses calc_pll_cs->ctx  # BOOM
 -> calc_pll_max_vco_construct()    <- sets calc_pll_cs->ctx

After:
dce110_clk_src_construct() does:
 -> sets clk_src->base.ctx = ctx;
 -> ss_info_from_atombios_create()
   -> get_ss_info_from_atombios()   <- uses clk_src->base.ctx

Closes: https://bugzilla.suse.com/show_bug.cgi?id=1271175
Closes: https://lore.kernel.org/all/a9ee54e6-2413-4156-9bde-d528ae3c63a3@kernel.org/
Fixes: 1296423bf23c ("drm/amd/display: define DC_LOGGER for logger")
Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: Lakha, Bhawanpreet <Bhawanpreet.Lakha@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Rodrigo Siqueira <siqueira@igalia.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: amd-gfx@lists.freedesktop.org
---
Cc: dri-devel@lists.freedesktop.org
---
 drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c b/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
index ecb8493ec523..d3f7aa853e3a 100644
--- a/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c
@@ -1513,6 +1513,10 @@ static const struct clock_source_funcs dce110_clk_src_funcs = {
         .get_dp_dto_frequency_100hz = get_dp_dto_frequency_100hz
 };
 
+/* calc_pll_cs->ctx is set only after get_ss_info_from_atombios(), unlike clk_src->base */
+#pragma push_macro("DC_LOGGER")
+#undef DC_LOGGER
+#define DC_LOGGER CTX->logger
 
 static void get_ss_info_from_atombios(
                 struct dce110_clk_src *clk_src,
@@ -1526,7 +1530,7 @@ static void get_ss_info_from_atombios(
         struct spread_spectrum_info *ss_info_cur;
         struct spread_spectrum_data *ss_data_cur;
         uint32_t i;
-       DC_LOGGER_INIT();
+
         if (ss_entries_num == NULL) {
                 DC_LOG_SYNC(
                         "Invalid entry !!!\n");
@@ -1631,6 +1635,8 @@ static void get_ss_info_from_atombios(
         kfree(ss_info);
 }
 
+#pragma pop_macro("DC_LOGGER")
+
 static void ss_info_from_atombios_create(
         struct dce110_clk_src *clk_src)
 {
--
2.55.0