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[92.176.231.205]) by smtp.gmail.com with ESMTPSA id i3-20020a5d5583000000b0031f82743e25sm1648384wrv.67.2023.11.17.00.59.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Nov 2023 00:59:08 -0800 (PST) From: Javier Martinez Canillas To: Maxime Ripard Cc: linux-kernel@vger.kernel.org, Sahaj Sarup , Daniel Vetter , David Airlie , Maarten Lankhorst , Thomas Zimmermann , dri-devel@lists.freedesktop.org Subject: Re: [PATCH 3/3] drm/ssd130x: Change "solomon,page-offset" property default value In-Reply-To: References: <20231116180743.2763021-1-javierm@redhat.com> <20231116180743.2763021-3-javierm@redhat.com> Date: Fri, 17 Nov 2023 09:59:08 +0100 Message-ID: <87bkbs21sz.fsf@minerva.mail-host-address-is-not-set> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Maxime Ripard writes: Hello Maxime, > On Thu, Nov 16, 2023 at 07:07:39PM +0100, Javier Martinez Canillas wrote: >> This is used to specify the page start address offset of the display RAM. >> >> The value is used as offset when setting the page start address with the >> SSD130X_SET_PAGE_RANGE command, and the driver currently sets its value to >> 1 if the property is not present in the Device Tree. >> >> But the datasheet mentions that the value on reset for the page start is a >> 0, so it makes more sense to also have 0 as the default value for the page >> offset if the property is not present. > > I can see the argument, but that's a DT ABI breaking change. > Yes, I know it's a DT ABI breaking change but what I'm trying to argue is that the DT binding schema isn't correct to start with. Even the RPi DTBO for this device (which I guess is used by most people with a SSD1306) has a property to explicitly set this to 0: ssd1306: oled@3c{ ... solomon,page-offset = <0>; ... }; https://github.com/raspberrypi/linux/blob/rpi-6.1.y/arch/arm/boot/dts/overlays/ssd1306-overlay.dts >> In fact, using a default value of 1 leads to the display not working when >> the emulated fbdev is attached to the framebuffer console. > > Could we fix that one instead? What is the issue about, exactly > This is the issue that Sahaj reported: https://twitter.com/sahajsarup/status/1725088484736766364 I can try to figure out how to make the fbcon to work with a page-offset=1 but didn't investigate since thought that 0 is a much better default. Just like the maximum resolution is the default if no width and height are set. > Maxime -- Best regards, Javier Martinez Canillas Core Platforms Red Hat