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([2401:4900:9397:bb62:5cb7:971b:ead7:8dc5]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ab36f4737esm3426729a91.7.2026.10.09.05.26.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Oct 2026 05:26:57 -0700 (PDT) From: chitranshmandhaniya@gmail.com To: hansg@kernel.org Cc: ilpo.jarvinen@linux.intel.com, platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org, Chitransh_Mandhaniya@dell.com Subject: [PATCH v3 0/2] platform/x86: dell-uart-backlight: fall back to PCH PWM on UART timeout Date: Fri, 9 Oct 2026 17:56:00 +0530 Message-ID: <20261009122602.56624-1-chitranshmandhaniya@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261009072401.52509-1-chitranshmandhaniya@gmail.com> References: <20261009072401.52509-1-chitranshmandhaniya@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Chitransh Mandhaniya Some Dell OptiPlex AIO 7410 (35W) ship with DELL0501 in ACPI but no physical UART scalar board, leaving the machine with zero backlight control after the UART probe times out. Patch 1 is a preparatory refactor that extracts the UART initialization sequence into dell_uart_bl_init() so the probe function can inspect its return value. Patch 2 adds a PCH PWM fallback path: when dell_uart_bl_init() returns -ETIMEDOUT, the driver reads the Intel PCH BLC_PWM registers and registers a BACKLIGHT_PLATFORM device. v2 -> v3: - Split into two patches: preparatory refactor + fallback (Ilpo) v1 -> v2: - Use __free(pci_dev_put) for automatic PCI device cleanup (Ilpo) - Replace 0x10 with SZ_16, add linux/sizes.h (Ilpo) - Name BIT(31) as PCH_BLC_PWM_ENABLE (Ilpo) - Fix double-space in block comment (Ilpo) - Reduce devm_backlight_device_register() to fewer lines (Ilpo) - Extract dell_uart_bl_init() for the normal UART backlight path so the probe function reads more clearly (Ilpo) Chitransh Mandhaniya (2): platform/x86: dell-uart-backlight: extract dell_uart_bl_init() from probe platform/x86: dell-uart-backlight: fall back to PCH PWM on UART timeout .../platform/x86/dell/dell-uart-backlight.c | 156 +++++++++++++++--- 1 file changed, 133 insertions(+), 23 deletions(-) -- 2.43.0