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Sat, 14 Nov 2026 08:05:53 -0800 (PST) Received: from at-Standard-PC-Q35-ICH9-2009 ([106.202.114.179]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1b505b5bf76sm13378548c88.10.2026.11.14.08.05.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 14 Nov 2026 08:05:53 -0800 (PST) From: Atharva Tiwari To: Cc: Atharva Tiwari , Sebastian Zygadlo , Yossef Osman , Andre Eikmeyer , Bjorn Helgaas , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)), "H. Peter Anvin" , Alex Deucher , =?UTF-8?q?Christian=20K=C3=B6nig?= , David Airlie , Simona Vetter , Harry Wentland , Leo Li , Rodrigo Siqueira , Kenneth Feng , Hans de Goede , =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= , linux-pci@vger.kernel.org (open list:PCI SUBSYSTEM), linux-kernel@vger.kernel.org (open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)), amd-gfx@lists.freedesktop.org (open list:RADEON and AMDGPU DRM DRIVERS), dri-devel@lists.freedesktop.org (open list:DRM DRIVERS), platform-driver-x86@vger.kernel.org (open list:X86 PLATFORM DRIVERS) Subject: [PATCH v2 01/12] platform/apple-gmux: Fix power for MMIO systems Date: Sat, 14 Nov 2026 11:03:48 -0500 Message-ID: <20261114160457.3034-2-atharvatiwarilinuxdev@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261114160457.3034-1-atharvatiwarilinuxdev@gmail.com> References: <20261114160457.3034-1-atharvatiwarilinuxdev@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Currently The dGPU on MMIO Systems, dies when we write the gmux values to turn off the gpu. On MMIO macs Using only gmux dosent work, instead we have to use PWRD method + GMUX, which turns off the entire bridge, and completely messes the pci config, so we can't use pci to traverse through it. we save the entire bridge using ACPI addresses then we run PWRD(1) to turn off the bridge, then we write gmux states, and resume we do the vice versa, but here we dont need to retrain the link and write the MMIO variable. Tested-by: Sebastian Zygadlo Tested-by: Yossef Osman Co-developed-by: Andre Eikmeyer Signed-off-by: Andre Eikmeyer Signed-off-by: Atharva Tiwari --- drivers/platform/x86/apple-gmux.c | 159 ++++++++++++++++++++++++++++-- 1 file changed, 152 insertions(+), 7 deletions(-) diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c index 9c728ac4e..34e94f2b2 100644 --- a/drivers/platform/x86/apple-gmux.c +++ b/drivers/platform/x86/apple-gmux.c @@ -65,6 +65,10 @@ struct apple_gmux_data { struct backlight_device *bdev; + /* power handling data */ + struct pci_dev *discrete_pdev; + enum apple_gmux_type type; + /* switcheroo data */ acpi_handle dhandle; int gpe; @@ -502,23 +506,158 @@ static int gmux_switch_ddc(enum vga_switcheroo_client_id id) /** * DOC: Power control * - * gmux is able to cut power to the discrete GPU. It automatically takes care + * gmux is able to cut power to the discrete GPU. On most + * Systems the gmux automatically takes care * of the correct sequence to tear down and bring up the power rails for * core voltage, VRAM and PCIe. + * + * But on MMIO systems, the standard gmux writes does not work instead we + * have to use a combination of ACPI and GMUX, + * and Using PWRD (the method that used in macOS to turn on/off the dGPU and its bridges), + * which turns off the entire bridge and messes up the PCI config, + * so we can't use pci_upstream_bridge to traverse + * through the bridge, so we use ACPI addresses to save/restore bridges. + * + * NOTE: Communication to these bridges (not the dGPU/HDA) in any form + * when the bridge is off, will result in CPU CATERR. */ +static int gmux_save_restore_pci(acpi_handle parent_handle, const char *name, + bool save, acpi_handle *out_handle) +{ + acpi_status status; + acpi_handle handle; + struct acpi_device *adev; + struct device *dev; + struct pci_dev *pdev; + + if (name) { + status = acpi_get_handle(parent_handle, name, &handle); + if (ACPI_FAILURE(status)) + return -EIO; + + if (out_handle) + *out_handle = handle; + } else + handle = parent_handle; + + adev = acpi_fetch_acpi_dev(handle); + if (!adev) + return -EIO; + + dev = acpi_get_first_physical_node(adev); + if (!dev || !dev_is_pci(dev)) + return -EIO; + + pdev = to_pci_dev(dev); + + if (save) { + pci_save_state(pdev); + pdev->current_state = PCI_D3cold; + } else { + pdev->current_state = PCI_D0; + pci_restore_state(pdev); + } + return 0; +} + static int gmux_set_discrete_state(struct apple_gmux_data *gmux_data, enum vga_switcheroo_state state) { reinit_completion(&gmux_data->powerchange_done); + acpi_handle discrete_handle; + acpi_status status; + unsigned long long result; + + if (!gmux_data->discrete_pdev) + return -ENODEV; + + discrete_handle = ACPI_HANDLE(&gmux_data->discrete_pdev->dev); + if (!discrete_handle) + return -ENODEV; if (state == VGA_SWITCHEROO_ON) { - gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 1); - gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 3); + if (gmux_data->type == APPLE_GMUX_TYPE_MMIO) { + acpi_handle handle; + u16 vendor; + int i; + + gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 2); + msleep(100); + gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 3); + + status = acpi_execute_simple_method(discrete_handle, "PWRD", 0); + if (ACPI_FAILURE(status)) + return -EIO; + msleep(20); + + if (gmux_save_restore_pci(NULL, "\\_SB_.PCI0.PEG0", 0, &handle)) + return -EIO; + + if (gmux_save_restore_pci(handle, "EGP0", 0, &handle)) + return -EIO; + + if (gmux_save_restore_pci(handle, "EGP1", 0, &handle)) + return -EIO; + + for (i = 0; i < 1000; i++) { + pci_read_config_word(gmux_data->discrete_pdev, + PCI_VENDOR_ID, &vendor); + if (vendor != 0xffff) + break; + msleep(1); + } + if (vendor == 0xffff) + return -ETIMEDOUT; + + if (gmux_save_restore_pci(handle, "GFX0", 0, NULL)) + return -EIO; + + if (gmux_save_restore_pci(handle, "HDAU", 0, NULL)) + return -EIO; + } else { + gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 1); + gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 3); + } pr_debug("Discrete card powered up\n"); } else { - gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 1); - gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 0); + if (gmux_data->type == APPLE_GMUX_TYPE_MMIO) { + acpi_handle parent_handle = discrete_handle; + bool saved_hda = false; + + /* If the power state was OFF, then we only do + * PWRD and we do not save registers, as the + * registers are already saved + */ + if (gmux_data->power_state == VGA_SWITCHEROO_OFF) + goto do_pwrd; + + while (ACPI_SUCCESS(acpi_get_parent(parent_handle, + &parent_handle))) { + if (!saved_hda) { + if (!gmux_save_restore_pci(parent_handle, + "HDAU", true, NULL)) { + saved_hda = true; + pci_save_state(gmux_data->discrete_pdev); + gmux_data->discrete_pdev->current_state = + PCI_D3cold; + } + } + if (gmux_save_restore_pci(parent_handle, NULL, true, NULL)) + break; + } +do_pwrd: + status = acpi_execute_simple_method(discrete_handle, "PWRD", 1); + if (ACPI_FAILURE(status)) + return -EIO; + msleep(20); + gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 1); + mdelay(10); + gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 0); + } else { + gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 1); + gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 0); + } pr_debug("Discrete card powered down\n"); } @@ -552,10 +691,14 @@ static enum vga_switcheroo_client_id gmux_get_client_id(struct pci_dev *pdev) else if (pdev->vendor == PCI_VENDOR_ID_NVIDIA && pdev->device == 0x0863) return VGA_SWITCHEROO_IGD; - else + else { + if (!apple_gmux_data->discrete_pdev) + apple_gmux_data->discrete_pdev = pci_dev_get(pdev); + return VGA_SWITCHEROO_DIS; -} + } +} static const struct vga_switcheroo_handler gmux_handler_no_ddc = { .switchto = gmux_switchto, .power_state = gmux_set_power_state, @@ -803,6 +946,7 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id) if (!gmux_data) return -ENOMEM; pnp_set_drvdata(pnp, gmux_data); + gmux_data->type = type; switch (type) { case APPLE_GMUX_TYPE_MMIO: @@ -993,6 +1137,7 @@ static void gmux_remove(struct pnp_dev *pnp) gmux_fini_debugfs(gmux_data); vga_switcheroo_unregister_handler(); + pci_dev_put(gmux_data->discrete_pdev); gmux_disable_interrupts(gmux_data); if (gmux_data->gpe >= 0) { acpi_disable_gpe(NULL, gmux_data->gpe); -- 2.55.0