drm/dp: Correctly mask DP_TRAINING_AUX_RD_INTERVAL values for DP 1.4
diff mbox

Message ID 1521219275-25802-1-git-send-email-matthew.s.atwood@intel.com
State New
Headers show

Commit Message

Matt Atwood March 16, 2018, 4:54 p.m. UTC
From: Matt Atwood <matthew.s.atwood@intel.com>

DP_TRAINING_AUX_RD_INTERVAL with DP 1.3 spec changed bit scheeme from 8
bits to 7 in DPCD 0x000e. The 8th bit is used to identify extended
receiver capabilities. For panels that use this new feature wait interval
would be increased by 512 ms, when spec is max 16 ms. This behavior is
described in table 2-158 of DP 1.4 spec address 0000eh.

With the introduction of DP 1.4 spec main link clock recovery was
standardized to 100 us regardless of TRAINING_AUX_RD_INTERVAL value.

To avoid breaking panels that are not spec compiant we now warn on
invalid values.

V2: commit title/message, masking all 7 bits, warn on out of spec values.
V3: commit message, make link train clock recovery follow DP 1.4 spec.
V4: style changes
V5: typo
V6: print statement revisions, DP_REV to DPCD_REV, comment correction
V7: typo
V8: Style

Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>
---
 drivers/gpu/drm/drm_dp_helper.c | 22 ++++++++++++++++++----
 include/drm/drm_dp_helper.h     |  6 ++++++
 2 files changed, 24 insertions(+), 4 deletions(-)

Comments

Jani Nikula March 19, 2018, 7:13 p.m. UTC | #1
On Fri, 16 Mar 2018, matthew.s.atwood@intel.com wrote:
> From: Matt Atwood <matthew.s.atwood@intel.com>
>
> DP_TRAINING_AUX_RD_INTERVAL with DP 1.3 spec changed bit scheeme from 8
> bits to 7 in DPCD 0x000e. The 8th bit is used to identify extended
> receiver capabilities. For panels that use this new feature wait interval
> would be increased by 512 ms, when spec is max 16 ms. This behavior is
> described in table 2-158 of DP 1.4 spec address 0000eh.
>
> With the introduction of DP 1.4 spec main link clock recovery was
> standardized to 100 us regardless of TRAINING_AUX_RD_INTERVAL value.
>
> To avoid breaking panels that are not spec compiant we now warn on
> invalid values.
>
> V2: commit title/message, masking all 7 bits, warn on out of spec values.
> V3: commit message, make link train clock recovery follow DP 1.4 spec.
> V4: style changes
> V5: typo
> V6: print statement revisions, DP_REV to DPCD_REV, comment correction
> V7: typo
> V8: Style
>
> Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>
> ---
>  drivers/gpu/drm/drm_dp_helper.c | 22 ++++++++++++++++++----
>  include/drm/drm_dp_helper.h     |  6 ++++++

This should be sent to dri-devel. See scripts/get_maintainer.pl.

BR,
Jani.
kernel test robot March 20, 2018, 12:56 a.m. UTC | #2
Hi Matt,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on v4.16-rc4]
[also build test ERROR on next-20180319]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/matthew-s-atwood-intel-com/drm-dp-Correctly-mask-DP_TRAINING_AUX_RD_INTERVAL-values-for-DP-1-4/20180319-073021
config: i386-allyesconfig (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   In file included from drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_link.c:42:0:
>> drivers/gpu/drm/amd/amdgpu/../display/include/dpcd_defs.h:32:2: error: expected identifier before numeric constant
     DPCD_REV_10 = 0x10,
     ^~~~

vim +32 drivers/gpu/drm/amd/amdgpu/../display/include/dpcd_defs.h

4562236b3b Harry Wentland 2017-09-12  30  
4562236b3b Harry Wentland 2017-09-12  31  enum dpcd_revision {
4562236b3b Harry Wentland 2017-09-12 @32  	DPCD_REV_10 = 0x10,
4562236b3b Harry Wentland 2017-09-12  33  	DPCD_REV_11 = 0x11,
4562236b3b Harry Wentland 2017-09-12  34  	DPCD_REV_12 = 0x12,
4562236b3b Harry Wentland 2017-09-12  35  	DPCD_REV_13 = 0x13,
4562236b3b Harry Wentland 2017-09-12  36  	DPCD_REV_14 = 0x14
4562236b3b Harry Wentland 2017-09-12  37  };
4562236b3b Harry Wentland 2017-09-12  38  

:::::: The code at line 32 was first introduced by commit
:::::: 4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c drm/amd/dc: Add dc display driver (v2)

:::::: TO: Harry Wentland <harry.wentland@amd.com>
:::::: CC: Alex Deucher <alexander.deucher@amd.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
kernel test robot March 20, 2018, 1:26 a.m. UTC | #3
Hi Matt,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on v4.16-rc4]
[also build test ERROR on next-20180319]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/matthew-s-atwood-intel-com/drm-dp-Correctly-mask-DP_TRAINING_AUX_RD_INTERVAL-values-for-DP-1-4/20180319-073021
config: ia64-allyesconfig (attached as .config)
compiler: ia64-linux-gcc (GCC) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=ia64 

All errors (new ones prefixed by >>):

   In file included from drivers/gpu/drm/amd/amdgpu/../display/include/dpcd_defs.h:29:0,
                    from drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_link.c:42:
>> include/drm/drm_dp_helper.h:67:45: error: expected identifier before numeric constant
    # define DPCD_REV_10                        0x10
                                                ^
   drivers/gpu/drm/amd/amdgpu/../display/include/dpcd_defs.h:32:2: note: in expansion of macro 'DPCD_REV_10'
     DPCD_REV_10 = 0x10,
     ^~~~~~~~~~~

vim +67 include/drm/drm_dp_helper.h

    63	
    64	/* AUX CH addresses */
    65	/* DPCD */
    66	#define DP_DPCD_REV                         0x000
  > 67	# define DPCD_REV_10                        0x10
    68	# define DPCD_REV_11                        0x11
    69	# define DPCD_REV_12                        0x12
    70	# define DPCD_REV_13                        0x13
    71	# define DPCD_REV_14                        0x14
    72	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Patch
diff mbox

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index adf79be..6bee2df 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -119,18 +119,32 @@  u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SI
 EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis);
 
 void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
-	if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
+	int rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] &
+			  DP_TRAINING_AUX_RD_MASK;
+
+	if (rd_interval > 4)
+		DRM_DEBUG_KMS("AUX interval %d, out of range (max 4)\n",
+			      rd_interval);
+
+	if (rd_interval == 0 || dpcd[DP_DPCD_REV] >= DPCD_REV_14)
 		udelay(100);
 	else
-		mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
+		mdelay(rd_interval * 4);
 }
 EXPORT_SYMBOL(drm_dp_link_train_clock_recovery_delay);
 
 void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
-	if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
+	int rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] &
+			  DP_TRAINING_AUX_RD_MASK;
+
+	if (rd_interval > 4)
+		DRM_DEBUG_KMS("AUX interval %d, out of range (max 4)\n",
+			      rd_interval);
+
+	if (rd_interval == 0)
 		udelay(400);
 	else
-		mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
+		mdelay(rd_interval * 4);
 }
 EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay);
 
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index da58a42..8c59ce4 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -64,6 +64,11 @@ 
 /* AUX CH addresses */
 /* DPCD */
 #define DP_DPCD_REV                         0x000
+# define DPCD_REV_10                        0x10
+# define DPCD_REV_11                        0x11
+# define DPCD_REV_12                        0x12
+# define DPCD_REV_13                        0x13
+# define DPCD_REV_14                        0x14
 
 #define DP_MAX_LINK_RATE                    0x001
 
@@ -118,6 +123,7 @@ 
 # define DP_DPCD_DISPLAY_CONTROL_CAPABLE     (1 << 3) /* edp v1.2 or higher */
 
 #define DP_TRAINING_AUX_RD_INTERVAL         0x00e   /* XXX 1.2? */
+# define DP_TRAINING_AUX_RD_MASK            0x7F    /* XXX 1.2? */
 
 #define DP_ADAPTER_CAP			    0x00f   /* 1.2 */
 # define DP_FORCE_LOAD_SENSE_CAP	    (1 << 0)