From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anatolij Gustschin Date: Fri, 22 May 2020 16:52:13 +0200 Subject: [PATCH 09/26] video: Add support for copying to a hardware framebuffer In-Reply-To: <20200519231058.19945-10-sjg@chromium.org> References: <20200519231058.19945-1-sjg@chromium.org> <20200519231058.19945-10-sjg@chromium.org> Message-ID: <20200522165213.3eda920d@crub> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On Tue, 19 May 2020 17:10:41 -0600 Simon Glass sjg at chromium.org wrote: > Some architectures use a cached framebuffer and flush the cache as needed > so that changes are visible. This is supported by U-Boot. > > However x86 uses an uncached framebuffer with a 'write-combining' feature > to speed up writes. Reads are permitted but they are extremely expensive. > > Unfortunately, reading from the frame buffer is quite common, e.g. to > scroll it. This makes scrolling very slow. > > Add a new feature which supports copying modified parts of the frame > buffer to the uncached hardware buffer. This speeds up scrolling by at > least 10x on x86 so the extra complexity cost seems worth it. > > As a starting point, add the Kconfig, update the video structures to keep > track of the buffer and add a function to do the copy. > > Signed-off-by: Simon Glass Reviewed-by: Anatolij Gustschin