[PATCH v4 1/2] drm/i915: Assume dual channel LVDS if pixel clock necessitates it

[PATCH v4 1/2] drm/i915: Assume dual channel LVDS if pixel clock necessitates it

[Lukas Wunner]

Single channel LVDS maxes out at 112 MHz, anything above must be dual
channel. This avoids the need to specify i915.lvds_channel_mode=2 on
all 17" MacBook Pro models with i915 graphics since they had 1920x1200
(193 MHz), plus those 15" pre-retina models which had a resolution
of 1680x1050 (119 MHz) as a BTO option.

v2: Avoid hardcoding 17" models by assuming dual channel LVDS if the
resolution necessitates it, suggested by Jani Nikula.

v3: Fix typo, thanks Joonas Lahtinen.

v4: Split commit in two, suggested by Ville Syrjälä.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Tested-by: Lukas Wunner <lukas@wunner.de>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: stable@vger.kernel.org
---

Notes:
    Source for 112 MHz limit of single channel LVDS is section 2.3 of:
    https://01.org/linuxgraphics/sites/default/files/documentation/ivb_ihd_os_vol3_part4.pdf

 drivers/gpu/drm/i915/intel_lvds.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index 5abda1d..ee621e3 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -848,6 +848,11 @@ static bool compute_is_dual_link_lvds(struct intel_lvds_encoder *lvds_encoder)
 	if (i915.lvds_channel_mode > 0)
 		return i915.lvds_channel_mode == 2;
 
+	/* single channel LVDS is limited to 112 MHz */
+	if (lvds_encoder->attached_connector->base.panel.fixed_mode->clock
+	    > 112999)
+		return true;
+
 	if (dmi_check_system(intel_dual_link_lvds))
 		return true;
 
@@ -1111,6 +1116,8 @@ void intel_lvds_init(struct drm_device *dev)
 out:
 	mutex_unlock(&dev->mode_config.mutex);
 
+	intel_panel_init(&intel_connector->panel, fixed_mode, downclock_mode);
+
 	lvds_encoder->is_dual_link = compute_is_dual_link_lvds(lvds_encoder);
 	DRM_DEBUG_KMS("detected %s-link lvds configuration\n",
 		      lvds_encoder->is_dual_link ? "dual" : "single");
@@ -1125,7 +1132,6 @@ out:
 	}
 	drm_connector_register(connector);
 
-	intel_panel_init(&intel_connector->panel, fixed_mode, downclock_mode);
 	intel_panel_setup_backlight(connector, INVALID_PIPE);
 
 	return;
-- 
1.8.5.2 (Apple Git-48)

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[PATCH v4 2/2] drm/i915: Add missing MacBook Pro models with dual channel LVDS

[Lukas Wunner]

Single channel LVDS maxes out at 112 MHz. The 15" pre-retina models
shipped with 1440x900 (106 MHz) by default or 1680x1050 (119 MHz)
as a BTO option, both versions used dual channel LVDS even though
the smaller one would have fit into a single channel.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Cc: stable@vger.kernel.org
---

Notes:
    Bug report showing that the MacBookPro8,2 with 1440x900 uses dual
    channel LVDS (this lead to it being hardcoded in intel_lvds.c by
    Daniel Vetter with commit 618563e3945b9d0864154bab3c607865b557cecc):
    https://bugzilla.kernel.org/show_bug.cgi?id=42842
    
    If i915.lvds_channel_mode=2 is missing even though the machine needs
    it, every other vertical line is white and consequently, only the left
    half of the screen is visible (verified by myself on a MacBookPro9,1).
    
    Forum posting concerning a MacBookPro6,2 with 1440x900, author is
    using i915.lvds_channel_mode=2 on the kernel command line, proving
    that the machine uses dual channels:
    https://bbs.archlinux.org/viewtopic.php?id=185770
    
    Chi Mei N154C6-L04 with 1440x900 is a replacement panel for all
    MacBook Pro "A1286" models, and that model number encompasses the
    MacBookPro6,2 / 8,2 / 9,1. Page 17 of the panel's datasheet shows
    it's driven with dual channel LVDS:
    http://www.ebay.com/itm/-/400690878560
    http://www.everymac.com/ultimate-mac-lookup/?search_keywords=A1286
    http://www.taopanel.com/chimei/datasheet/N154C6-L04.pdf
    
    Those three 15" models, MacBookPro6,2 / 8,2 / 9,1, are the only
    ones with i915 graphics and dual channel LVDS, so that list should
    be complete. And the 8,2 is already in intel_lvds.c.
    
    Possible motivation to use dual channel LVDS even on the 1440x900
    models: Reduce the number of different parts, i.e. use identical
    logic boards and display cabling on both versions and the only
    differing component is the panel.

 drivers/gpu/drm/i915/intel_lvds.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index ee621e3..fbcc7df 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -813,12 +813,28 @@ static int intel_dual_link_lvds_callback(const struct dmi_system_id *id)
 static const struct dmi_system_id intel_dual_link_lvds[] = {
 	{
 		.callback = intel_dual_link_lvds_callback,
-		.ident = "Apple MacBook Pro (Core i5/i7 Series)",
+		.ident = "Apple MacBook Pro 15\" (2010)",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro6,2"),
+		},
+	},
+	{
+		.callback = intel_dual_link_lvds_callback,
+		.ident = "Apple MacBook Pro 15\" (2011)",
 		.matches = {
 			DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
 			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro8,2"),
 		},
 	},
+	{
+		.callback = intel_dual_link_lvds_callback,
+		.ident = "Apple MacBook Pro 15\" (2012)",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro9,1"),
+		},
+	},
 	{ }	/* terminating entry */
 };
 
-- 
1.8.5.2 (Apple Git-48)

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Re: [PATCH v4 2/2] drm/i915: Add missing MacBook Pro models with dual channel LVDS

[Jani Nikula]

On Mon, 04 May 2015, Lukas Wunner <lukas@wunner.de> wrote:
> Single channel LVDS maxes out at 112 MHz. The 15" pre-retina models
> shipped with 1440x900 (106 MHz) by default or 1680x1050 (119 MHz)
> as a BTO option, both versions used dual channel LVDS even though
> the smaller one would have fit into a single channel.
>
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> Acked-by: Jani Nikula <jani.nikula@intel.com>
> Cc: stable@vger.kernel.org

Both pushed to drm-intel-fixes, with the notes moved into the commit
messages for posterity. There'll be others doing archeology on this! ;)

Thanks for the patches and review.

BR,
Jani.



> ---
>
> Notes:
>     Bug report showing that the MacBookPro8,2 with 1440x900 uses dual
>     channel LVDS (this lead to it being hardcoded in intel_lvds.c by
>     Daniel Vetter with commit 618563e3945b9d0864154bab3c607865b557cecc):
>     https://bugzilla.kernel.org/show_bug.cgi?id=42842
>     
>     If i915.lvds_channel_mode=2 is missing even though the machine needs
>     it, every other vertical line is white and consequently, only the left
>     half of the screen is visible (verified by myself on a MacBookPro9,1).
>     
>     Forum posting concerning a MacBookPro6,2 with 1440x900, author is
>     using i915.lvds_channel_mode=2 on the kernel command line, proving
>     that the machine uses dual channels:
>     https://bbs.archlinux.org/viewtopic.php?id=185770
>     
>     Chi Mei N154C6-L04 with 1440x900 is a replacement panel for all
>     MacBook Pro "A1286" models, and that model number encompasses the
>     MacBookPro6,2 / 8,2 / 9,1. Page 17 of the panel's datasheet shows
>     it's driven with dual channel LVDS:
>     http://www.ebay.com/itm/-/400690878560
>     http://www.everymac.com/ultimate-mac-lookup/?search_keywords=A1286
>     http://www.taopanel.com/chimei/datasheet/N154C6-L04.pdf
>     
>     Those three 15" models, MacBookPro6,2 / 8,2 / 9,1, are the only
>     ones with i915 graphics and dual channel LVDS, so that list should
>     be complete. And the 8,2 is already in intel_lvds.c.
>     
>     Possible motivation to use dual channel LVDS even on the 1440x900
>     models: Reduce the number of different parts, i.e. use identical
>     logic boards and display cabling on both versions and the only
>     differing component is the panel.
>
>  drivers/gpu/drm/i915/intel_lvds.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
> index ee621e3..fbcc7df 100644
> --- a/drivers/gpu/drm/i915/intel_lvds.c
> +++ b/drivers/gpu/drm/i915/intel_lvds.c
> @@ -813,12 +813,28 @@ static int intel_dual_link_lvds_callback(const struct dmi_system_id *id)
>  static const struct dmi_system_id intel_dual_link_lvds[] = {
>  	{
>  		.callback = intel_dual_link_lvds_callback,
> -		.ident = "Apple MacBook Pro (Core i5/i7 Series)",
> +		.ident = "Apple MacBook Pro 15\" (2010)",
> +		.matches = {
> +			DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
> +			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro6,2"),
> +		},
> +	},
> +	{
> +		.callback = intel_dual_link_lvds_callback,
> +		.ident = "Apple MacBook Pro 15\" (2011)",
>  		.matches = {
>  			DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
>  			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro8,2"),
>  		},
>  	},
> +	{
> +		.callback = intel_dual_link_lvds_callback,
> +		.ident = "Apple MacBook Pro 15\" (2012)",
> +		.matches = {
> +			DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
> +			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro9,1"),
> +		},
> +	},
>  	{ }	/* terminating entry */
>  };
>  
> -- 
> 1.8.5.2 (Apple Git-48)
>

-- 
Jani Nikula, Intel Open Source Technology Center
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