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Mon, 05 May 2025 00:25:01 -0700 (PDT) Received: from localhost.localdomain ([27.67.185.150]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22e1522fa58sm48014325ad.242.2025.05.05.00.24.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 05 May 2025 00:25:00 -0700 (PDT) From: Nam Tran To: pavel@ucw.cz Cc: andy@kernel.org, geert@linux-m68k.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, christophe.jaillet@wanadoo.fr, corbet@lwn.net, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, florian.fainelli@broadcom.com, bcm-kernel-feedback-list@broadcom.com, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v8 0/5] auxdisplay: add support for TI LP5812 4x3 Matrix LED driver Date: Mon, 5 May 2025 14:24:33 +0700 Message-Id: <20250505072433.8193-1-trannamatk@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Wed, 30 Apr 2025 Pavel Machek wrote: > > > > > Is it intended to be used as a 4x3 matrix, or is this just an internal > > > > > wiring detail, and should it be exposed as 12 individual LEDs instead? > > > > > > > > The 4×3 matrix is a real and fundamental aspect of the LP5812’s operation. > > > > It is not just an internal wiring detail. > > > > The device adopts a Time-Cross-Multiplexing (TCM) structure, where 4 output > > > > pins control 12 LED dots individually through scanning. Each pin includes > > > > both high-side and low-side drive circuits, meaning matrix multiplexing is > > > > required for proper operation — it cannot be treated as 12 completely > > > > independent LEDs. > > > > > > Scanning is really a detail. > > > > > > If this is used as rectangular 4x3 display, then it goes to auxdisplay. > > > > > > If this is used as a power LED, SD activity LED, capslock and numlock > > > ... placed randomly all around the device, then it goes LED subsystem. > > > > The LP5812 is used for LED status indication in devices like smart speakers, > > wearables, and routers, not as a structured rectangular display. > > Well, IIRC it also supports automated animations, and that does not > make sense on LED indicators. So... what device do _you_ have and how > exactly is it used there? We’re using the LP5812 in a battery-powered smart speaker as a status indicator with visually enhanced lighting — for example, breathing effects during standby and fading effects during voice processing. While the LP5812 supports autonomous animations, they’re used here to offload real-time brightness control from the main controller. Each LED’s animation engine enables smooth transitions like fade-in/fade-out and breathing effects. These patterns are configured once and run autonomously, saving MCU load and power, while still serving traditional indicator roles. Best regards, Nam Tran