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Sat, 24 Oct 2026 21:03:01 -0700 (PDT) Received: from at-Standard-PC-Q35-ICH9-2009 ([106.221.76.40]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-198a32ff780sm11635283c88.22.2026.10.24.21.02.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 24 Oct 2026 21:03:01 -0700 (PDT) From: Atharva Tiwari To: Cc: Atharva Tiwari , 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?= , Andre Eikmeyer , 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 07/13] platform/apple-gmux: Add check to detect FSS Date: Sat, 24 Oct 2026 23:59:43 -0400 Message-ID: <20261025040046.1602-8-atharvatiwarilinuxdev@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261025040046.1602-1-atharvatiwarilinuxdev@gmail.com> References: <20261025040046.1602-1-atharvatiwarilinuxdev@gmail.com> X-Mailing-List: platform-driver-x86@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 On MMIO macs, there is feature called FSS, we assume its a display syncing technology between internal links (for example 5K iMacs). We detect it and then warn the user about it, if its broken/unavailable. Signed-off-by: Atharva Tiwari --- drivers/platform/x86/apple-gmux.c | 2 ++ include/linux/apple-gmux.h | 1 + 2 files changed, 3 insertions(+) diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c index 6a9580f27..dda281f2f 100644 --- a/drivers/platform/x86/apple-gmux.c +++ b/drivers/platform/x86/apple-gmux.c @@ -1224,6 +1224,8 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id) else if (boot_gpu == 1) gmux_switchto(VGA_SWITCHEROO_DIS); + if (type == APPLE_GMUX_TYPE_MMIO && gmux_read8(gmux_data, GMUX_PORT_FSS) & 1) + pr_warn("FSS Failure, display tearing expected\n"); /* * Retina MacBook Pros cannot switch the panel's AUX separately * and need eDP pre-calibration. They are distinguishable from diff --git a/include/linux/apple-gmux.h b/include/linux/apple-gmux.h index 206d97ffd..a4fa84500 100644 --- a/include/linux/apple-gmux.h +++ b/include/linux/apple-gmux.h @@ -22,6 +22,7 @@ #define GMUX_PORT_VERSION_RELEASE 0x06 #define GMUX_PORT_SWITCH_DISPLAY 0x10 #define GMUX_PORT_SWITCH_GET_DISPLAY 0x11 +#define GMUX_PORT_FSS 0x12 #define GMUX_PORT_INTERRUPT_ENABLE 0x14 #define GMUX_PORT_INTERRUPT_STATUS 0x16 #define GMUX_PORT_SWITCH_DDC 0x28 -- 2.55.0