From 0e76718923ca71548636bf02adc48e6104e4fb05 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Fri, 25 Apr 2014 20:14:31 +0300 Subject: [PATCH] drm/i915: Add a brief description of the VLV display PHY internals MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Document the internal structure of the VLV display PHY a bit to help people understand how the different register blocks relate to each other. v2: Add a bit more text Make it a DOC: comment, but leave the ascii art out since it would get mangled Signed-off-by: Ville Syrjälä Reviewed-by: Chon Ming Lee Signed-off-by: Daniel Vetter --- Documentation/DocBook/drm.tmpl | 4 ++ drivers/gpu/drm/i915/i915_reg.h | 85 +++++++++++++++++++++++++++++++-- 2 files changed, 85 insertions(+), 4 deletions(-) diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl index 62573c17091d..b4f12d455166 100644 --- a/Documentation/DocBook/drm.tmpl +++ b/Documentation/DocBook/drm.tmpl @@ -2937,6 +2937,10 @@ int num_ioctls; probing, so those sections fully apply. + + DPIO +!Pdrivers/gpu/drm/i915/i915_reg.h DPIO + diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h index bab5d17f67d1..9b3681ee4a69 100644 --- a/drivers/gpu/drm/i915/i915_reg.h +++ b/drivers/gpu/drm/i915/i915_reg.h @@ -575,12 +575,89 @@ enum punit_power_well { #define DSI_PLL_M1_DIV_MASK (0x1ff << 0) #define CCK_DISPLAY_CLOCK_CONTROL 0x6b -/* - * DPIO - a special bus for various display related registers to hide behind +/** + * DOC: DPIO + * + * VLV and CHV have slightly peculiar display PHYs for driving DP/HDMI + * ports. DPIO is the name given to such a display PHY. These PHYs + * don't follow the standard programming model using direct MMIO + * registers, and instead their registers must be accessed trough IOSF + * sideband. VLV has one such PHY for driving ports B and C, and CHV + * adds another PHY for driving port D. Each PHY responds to specific + * IOSF-SB port. + * + * Each display PHY is made up of one or two channels. Each channel + * houses a common lane part which contains the PLL and other common + * logic. CH0 common lane also contains the IOSF-SB logic for the + * Common Register Interface (CRI) ie. the DPIO registers. CRI clock + * must be running when any DPIO registers are accessed. + * + * In addition to having their own registers, the PHYs are also + * controlled through some dedicated signals from the display + * controller. These include PLL reference clock enable, PLL enable, + * and CRI clock selection, for example. + * + * Eeach channel also has two splines (also called data lanes), and + * each spline is made up of one Physical Access Coding Sub-Layer + * (PCS) block and two TX lanes. So each channel has two PCS blocks + * and four TX lanes. The TX lanes are used as DP lanes or TMDS + * data/clock pairs depending on the output type. + * + * Additionally the PHY also contains an AUX lane with AUX blocks + * for each channel. This is used for DP AUX communication, but + * this fact isn't really relevant for the driver since AUX is + * controlled from the display controller side. No DPIO registers + * need to be accessed during AUX communication, + * + * Generally the common lane corresponds to the pipe and + * the spline (PCS/TX) correponds to the port. + * + * For dual channel PHY (VLV/CHV): + * + * pipe A == CMN/PLL/REF CH0 * - * DPIO is VLV only. + * pipe B == CMN/PLL/REF CH1 + * + * port B == PCS/TX CH0 + * + * port C == PCS/TX CH1 + * + * This is especially important when we cross the streams + * ie. drive port B with pipe B, or port C with pipe A. + * + * For single channel PHY (CHV): + * + * pipe C == CMN/PLL/REF CH0 + * + * port D == PCS/TX CH0 + * + * Note: digital port B is DDI0, digital port C is DDI1, + * digital port D is DDI2 + */ +/* + * Dual channel PHY (VLV/CHV) + * --------------------------------- + * | CH0 | CH1 | + * | CMN/PLL/REF | CMN/PLL/REF | + * |---------------|---------------| Display PHY + * | PCS01 | PCS23 | PCS01 | PCS23 | + * |-------|-------|-------|-------| + * |TX0|TX1|TX2|TX3|TX0|TX1|TX2|TX3| + * --------------------------------- + * | DDI0 | DDI1 | DP/HDMI ports + * --------------------------------- * - * Note: digital port B is DDI0, digital pot C is DDI1 + * Single channel PHY (CHV) + * ----------------- + * | CH0 | + * | CMN/PLL/REF | + * |---------------| Display PHY + * | PCS01 | PCS23 | + * |-------|-------| + * |TX0|TX1|TX2|TX3| + * ----------------- + * | DDI2 | DP/HDMI port + * ----------------- */ #define DPIO_DEVFN 0 -- 2.20.1