On Mon, Jan 04, 2016 at 05:52:06PM +0100, Lukas Wunner wrote: > Document what I've learned so far about the gmux so that we can > collaboratively reverse-engineer its remaining unknown bits > without everyone having to start from scratch. > +Jon Corbet +Daniel Vetter +linux-doc Any concerns with this series? If not, I'll take it in via the pdx86 tree. Thanks, Darren > The DOC sections are bound together in the gpu.tmpl DocBook > under a new vga_switcheroo "Handlers" chapter. Eventually > this should be amended with documentation about the four other > handlers that exist so far (nouveau v1 DSM, nouveau Optimus DSM, > radeon ATPX, amdgpu ATPX). > > Requires kernel-doc with asciidoc support. > > The EFI variable was reverse-engineered by Bruno Bierbaumer > <bruno@xxxxxxxxxxxxxx> and Andreas Heider <andreas@xxxxxxxx>. > > Some of the remaining open questions: > > * How are vblank intervals synchronized on retinas to achieve seamless > switching? Is the DP mux capable of this? It's not mentioned in the > data sheets. Or is it done at the OS level, i.e. do we have to > synchronize vblank intervals between DRM drivers? There's a signal > coming from the panel connector and going into gmux, could this be > the vblank signal as received by the panel to properly time the > switch? > > * On retinas there's an I2C bus between gmux and the connector of the > right I/O board, apparently leading to the Parade PS8401A HDMI > repeater. What is this for, is it controlled via gmux registers? > Data sheet: > http://www.paradetech.com/products/jitter-cleaning-repeaters/ps8401/ > > * On retinas there's an I2C bus between gmux and the LED driver. > Pre-retinas connected the LED driver to SMBUS. Are there additional > gmux registers on retinas to control it? > > * The MacPro6,1 2013 also has a gmux, the same Renesas R4F2113 as the > retina MacBook Pro. The Mac Pro doesn't have a built-in display, > so what is its purpose? Power control of the dual FirePro GPUs? > Switching of the external DP/Thunderbolt ports? The iFixit teardown > clearly shows one TI HD3SS212 DisplayPort mux on the logic board next > to one of the three Thunderbolt controllers. However six muxes would > be necessary to switch all six ports between GPUs. The mux is probably > necessary for one of the display configurations allowed by Apple, > but which one? > https://www.ifixit.com/Teardown/Mac+Pro+Late+2013+Teardown/20778 > https://d3nevzfk7ii3be.cloudfront.net/igi/fELBTnt31QhnDsqq.huge > https://support.apple.com/en-us/HT202801 > > * Registers we haven't decoded yet: > 0x700 32 Bit configmap? > 0x708 32 Bit power sequence? > 0x712 8 Bit status of clock from panel on retinas? > 0x713 8 Bit dito? > 0x724 16 Bit backlight, raw value? > 0x760 32 Bit backlight > 0x764 32 Bit backlight > 0x768 8 Bit backlight > 0x76a 16 Bit backlight > 0x76c 16 Bit backlight > 0x76e 16 Bit backlight > 0x77f edp/dp/hdmi probe? retina only. > > Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx> > --- > Documentation/DocBook/gpu.tmpl | 22 ++++++++ > drivers/platform/x86/apple-gmux.c | 113 ++++++++++++++++++++++++++++++++++++++ > 2 files changed, 135 insertions(+) > > diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl > index 225a246..9e95aa1 100644 > --- a/Documentation/DocBook/gpu.tmpl > +++ b/Documentation/DocBook/gpu.tmpl > @@ -3658,8 +3658,30 @@ int num_ioctls;</synopsis> > </sect1> > </chapter> > > + <chapter id="handlers"> > + <title>Handlers</title> > + <sect1> > + <title>apple-gmux Handler</title> > +!Pdrivers/platform/x86/apple-gmux.c Overview > +!Pdrivers/platform/x86/apple-gmux.c Interrupt > + <sect2> > + <title>Graphics mux</title> > +!Pdrivers/platform/x86/apple-gmux.c Graphics mux > + </sect2> > + <sect2> > + <title>Power control</title> > +!Pdrivers/platform/x86/apple-gmux.c Power control > + </sect2> > + <sect2> > + <title>Backlight control</title> > +!Pdrivers/platform/x86/apple-gmux.c Backlight control > + </sect2> > + </sect1> > + </chapter> > + > !Cdrivers/gpu/vga/vga_switcheroo.c > !Cinclude/linux/vga_switcheroo.h > +!Cdrivers/platform/x86/apple-gmux.c > </part> > > </book> > diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c > index aa58d41..f236250 100644 > --- a/drivers/platform/x86/apple-gmux.c > +++ b/drivers/platform/x86/apple-gmux.c > @@ -3,6 +3,7 @@ > * > * Copyright (C) Canonical Ltd. <seth.forshee@xxxxxxxxxxxxx> > * Copyright (C) 2010-2012 Andreas Heider <andreas@xxxxxxxx> > + * Copyright (C) 2015 Lukas Wunner <lukas@xxxxxxxxx> > * > * This program is free software; you can redistribute it and/or modify > * it under the terms of the GNU General Public License version 2 as > @@ -26,6 +27,24 @@ > #include <acpi/video.h> > #include <asm/io.h> > > +/** > + * DOC: Overview > + * > + * :1: http://www.latticesemi.com/en/Products/FPGAandCPLD/LatticeXP2.aspx > + * :2: http://www.renesas.com/products/mpumcu/h8s/h8s2100/h8s2113/index.jsp > + * > + * gmux is a microcontroller built into the MacBook Pro to support dual GPUs: > + * A {1}[Lattice XP2] on pre-retinas, a {2}[Renesas R4F2113] on retinas. > + * > + * (The MacPro6,1 2013 also has a gmux, however it is unclear why since it has > + * dual GPUs but no built-in display.) > + * > + * gmux is connected to the LPC bus of the southbridge. Its I/O ports are > + * accessed differently depending on the microcontroller: Driver functions > + * to access a pre-retina gmux are infixed `_pio_`, those for a retina gmux > + * are infixed `_index_`. > + */ > + > struct apple_gmux_data { > unsigned long iostart; > unsigned long iolen; > @@ -247,6 +266,20 @@ static bool gmux_is_indexed(struct apple_gmux_data *gmux_data) > return false; > } > > +/** > + * DOC: Backlight control > + * > + * :3: http://www.ti.com/lit/ds/symlink/lp8543.pdf > + * :4: http://www.ti.com/lit/ds/symlink/lp8545.pdf > + * > + * On single GPU MacBooks, the PWM signal for the backlight is generated by > + * the GPU. On dual GPU MacBook Pros by contrast, either GPU may be suspended > + * to conserve energy. Hence the PWM signal needs to be generated by a separate > + * backlight driver which is controlled by gmux. The earliest generation > + * MBP5 2008/09 uses a {3}[TI LP8543] backlight driver. All newer models > + * use a {4}[TI LP8545]. > + */ > + > static int gmux_get_brightness(struct backlight_device *bd) > { > struct apple_gmux_data *gmux_data = bl_get_data(bd); > @@ -273,6 +306,68 @@ static const struct backlight_ops gmux_bl_ops = { > .update_status = gmux_update_status, > }; > > +/** > + * DOC: Graphics mux > + * > + * :5: http://pimg-fpiw.uspto.gov/fdd/07/870/086/0.pdf > + * :6: http://www.nxp.com/documents/data_sheet/CBTL06141.pdf > + * :7: http://www.ti.com/lit/ds/symlink/hd3ss212.pdf > + * :8: https://www.pericom.com/assets/Datasheets/PI3VDP12412.pdf > + * :9: http://www.ti.com/lit/ds/symlink/sn74lv4066a.pdf > + * :10: http://pdf.datasheetarchive.com/indexerfiles/Datasheets-SW16/DSASW00308511.pdf > + * :11: http://www.ti.com/lit/ds/symlink/ts3ds10224.pdf > + * > + * On pre-retinas, the LVDS outputs of both GPUs feed into gmux which muxes > + * either of them to the panel. One of the tricks gmux has up its sleeve is > + * to lengthen the blanking interval of its output during a switch to > + * synchronize it with the GPU switched to. This allows for a flicker-free > + * switch that is imperceptible by the user ({5}[US 8,687,007 B2]). > + * > + * On retinas, muxing is no longer done by gmux itself, but by a separate > + * chip which is controlled by gmux. The chip is triple sourced, it is > + * either an {6}[NXP CBTL06142], {7}[TI HD3SS212] or {8}[Pericom PI3VDP12412]. > + * The panel is driven with eDP instead of LVDS since the pixel clock > + * required for retina resolution exceeds LVDS' limits. > + * > + * Pre-retinas are able to switch the panel's DDC pins separately. > + * This is handled by a {9}[TI SN74LV4066A] which is controlled by gmux. > + * The inactive GPU can thus probe the panel's EDID without switching over > + * the entire panel. Retinas lack this functionality as the chips used for > + * eDP muxing are incapable of switching the AUX channel separately (see > + * the linked data sheets, Pericom would be capable but this is unused). > + * However the retina panel has the NO_AUX_HANDSHAKE_LINK_TRAINING bit set > + * in its DPCD, allowing the inactive GPU to skip the AUX handshake and > + * set up the output with link parameters pre-calibrated by the active GPU. > + * > + * The external DP port is only fully switchable on the first two unibody > + * MacBook Pro generations, MBP5 2008/09 and MBP6 2010. This is done by an > + * {6}[NXP CBTL06141] which is controlled by gmux. It's the predecessor of the > + * eDP mux on retinas, the difference being support for 2.7 versus 5.4 Gbit/s. > + * > + * The following MacBook Pro generations replaced the external DP port with a > + * combined DP/Thunderbolt port and lost the ability to switch it between GPUs, > + * connecting it either to the discrete GPU or the Thunderbolt controller. > + * Oddly enough, while the full port is no longer switchable, AUX and HPD > + * are still switchable by way of an {10}[NXP CBTL03062] (on pre-retinas > + * MBP8 2011 and MBP9 2012) or two {11}[TI TS3DS10224] (on retinas) under the > + * control of gmux. Since the integrated GPU is missing the main link, > + * external displays appear to it as phantoms which fail to link-train. > + * > + * gmux receives the HPD signal of all display connectors and sends an > + * interrupt on hotplug. On generations which cannot switch external ports, > + * the discrete GPU can then be woken to drive the newly connected display. > + * The ability to switch AUX on these generations could be used to improve > + * reliability of hotplug detection by having the integrated GPU poll the > + * ports while the discrete GPU is asleep, but currently we do not make use > + * of this feature. > + * > + * gmux' initial switch state on bootup is user configurable via the EFI > + * variable `gpu-power-prefs-fa4ce28d-b62f-4c99-9cc3-6815686e30f9` (5th byte, > + * 1 = IGD, 0 = DIS). Based on this setting, the EFI firmware tells gmux to > + * switch the panel and the external DP connector and allocates a framebuffer > + * for the selected GPU. > + */ > + > static int gmux_switchto(enum vga_switcheroo_client_id id) > { > if (id == VGA_SWITCHEROO_IGD) { > @@ -288,6 +383,14 @@ static int gmux_switchto(enum vga_switcheroo_client_id id) > return 0; > } > > +/** > + * DOC: Power control > + * > + * gmux is able to cut power to the discrete GPU. It automatically takes care > + * of the correct sequence to tear down and bring up the power rails for > + * core voltage, VRAM and PCIe. > + */ > + > static int gmux_set_discrete_state(struct apple_gmux_data *gmux_data, > enum vga_switcheroo_state state) > { > @@ -352,6 +455,16 @@ static const struct vga_switcheroo_handler gmux_handler = { > .get_client_id = gmux_get_client_id, > }; > > +/** > + * DOC: Interrupt > + * > + * gmux is also connected to a GPIO pin of the southbridge and thereby is able > + * to trigger an ACPI GPE. On the MBP5 2008/09 it's GPIO pin 22 of the Nvidia > + * MCP79, on all following generations it's GPIO pin 6 of the Intel PCH. > + * The GPE merely signals that an interrupt occurred, the actual type of event > + * is identified by reading a gmux register. > + */ > + > static inline void gmux_disable_interrupts(struct apple_gmux_data *gmux_data) > { > gmux_write8(gmux_data, GMUX_PORT_INTERRUPT_ENABLE, > -- > 1.8.5.2 (Apple Git-48) > > -- > To unsubscribe from this list: send the line "unsubscribe platform-driver-x86" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Darren Hart Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe platform-driver-x86" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
