From patchwork Fri Mar 22 05:17:57 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yifeng Li X-Patchwork-Id: 10864907 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 986F91575 for ; Fri, 22 Mar 2019 05:19:02 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7D8832A5D4 for ; Fri, 22 Mar 2019 05:19:02 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 718F22A5E2; Fri, 22 Mar 2019 05:19:02 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C5C242A5D4 for ; Fri, 22 Mar 2019 05:19:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727689AbfCVFSl (ORCPT ); Fri, 22 Mar 2019 01:18:41 -0400 Received: from tomli.me ([153.92.126.73]:58774 "EHLO tomli.me" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727672AbfCVFSl (ORCPT ); Fri, 22 Mar 2019 01:18:41 -0400 Received: from tomli.me (localhost [127.0.0.1]) by tomli.me (OpenSMTPD) with ESMTP id 6dec5519; Fri, 22 Mar 2019 05:18:36 +0000 (UTC) X-HELO: localhost.lan Authentication-Results: tomli.me; auth=pass (login) smtp.auth=tomli Received: from Unknown (HELO localhost.lan) (2402:f000:1:1501:200:5efe:dddb:8cda) by tomli.me (qpsmtpd/0.95) with ESMTPSA (DHE-RSA-CHACHA20-POLY1305 encrypted); Fri, 22 Mar 2019 05:18:36 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed; d=tomli.me; h=from:to:cc:subject:date:message-id:in-reply-to:references:mime-version:content-transfer-encoding; s=1490979754; bh=ymwVquARYH25vOe0O0vYizscGzeglujnl89fDE4zx3I=; b=kt2n+ny+dKi3hEREliTN1XJapS1eaqIkSsPrxneYWfJ+B3xh0+3tkoDYptb0efaYd/thuJuMJYmKwM1hMdnSUbXEVE0zv0Ygi4rFWlvofMWl/8xOqFWG9CJMm3x36M2JerTBkHs3rJqPtYv4b3B5aAd1qajX7U7sIQd0/18HXXDSzTDanoC99ndhHLAk7WxykUbGSk9QocwOG7iciYYF3W3gVe58r5zb2qCvAbncS6OD7qVP2AepyqCwz67Uo2KCP3wsMzKR0F/pa4dCw8yG43mwrgz0jJRiBTHFYnZSRd8nyS5P9xnXigu4si4MMt4v9oc04I6NkgXt8ZMfdY8myQ== From: Yifeng Li To: Sudip Mukherjee , Teddy Wang , linux-kernel@vger.kernel.org Cc: Bartlomiej Zolnierkiewicz , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, Yifeng Li Subject: [PATCH v2 5/7] Documentation: fb: sm712fb: add information mainly about 2D. Date: Fri, 22 Mar 2019 13:17:57 +0800 Message-Id: <20190322051759.15007-6-tomli@tomli.me> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190322051759.15007-1-tomli@tomli.me> References: <20190322051759.15007-1-tomli@tomli.me> MIME-Version: 1.0 Sender: linux-fbdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This commits add information about 32-bit color, 2D acceleration, as well as adding additional, general information about the hardware and many existing problems of the sm712fb driver. Signed-off-by: Yifeng Li --- Documentation/fb/sm712fb.txt | 123 +++++++++++++++++++++++++++++++---- 1 file changed, 110 insertions(+), 13 deletions(-) diff --git a/Documentation/fb/sm712fb.txt b/Documentation/fb/sm712fb.txt index c388442edf51..906b48aa40e4 100644 --- a/Documentation/fb/sm712fb.txt +++ b/Documentation/fb/sm712fb.txt @@ -1,31 +1,128 @@ What is sm712fb? ================= -This is a graphics framebuffer driver for Silicon Motion SM712 based processors. +"sm712fb" is a graphics framebuffer driver for Silicon Motion SM710 (LynxEM), +SM712 (LynxEM+), and SM720 (Lynx3DM, Lynx3DM+, aka. LynxEM4+) series of +video controllers. This series of video controller is a legacy from ~1998, +and was used on many classic, "prehistoric" laptops from 1998-2004, such as +IBM Thinkpad S30 and 240X. It was also used on some servers, industrial +computers, x86 and non-x86 embedded devices where only basic graphics was +needed. + +Notably, Lemote YeeLoong 8089, a MIPS laptop based on the Chinese Loongson +2F MIPS processor, is also using this chip because of hardware constraints, +and at a time, somewhat popular in the free software community due the +fact that it was the first laptop powered exclusively by free software, +and it was also an inexpensive platform for non-x86 hobbyists to explore. How to use it? ============== -Switching modes is done using the video=sm712fb:... boot parameter. - -If you want, for example, enable a resolution of 1280x1024x24bpp you should -pass to the kernel this command line: "video=sm712fb:0x31B". +You should not compile-in vesafb, since SM7xx can be used in a VGA +compatible mode, resulting conflicts with this driver. In addition, +the VGA compatible mode was never tested by the maintainers. -You should not compile-in vesafb. +Currently, the driver supports 3 modes: 640x480, 800x600, 1024x768, +at 16, 24 or 32-bit depth. Switching modes is done using the +`video=sm712fb:0x___` boot parameter. If you want, for example, +enable a resolution of 1280x1024x24bpp, you should pass to the kernel +this command line: "video=sm712fb:0x31B". -Currently supported video modes are: +Please consult the following table for the hexadecimal codes of +different modes. [Graphic modes] -bpp | 640x480 800x600 1024x768 1280x1024 -----+-------------------------------------------- - 8 | 0x301 0x303 0x305 0x307 - 16 | 0x311 0x314 0x317 0x31A - 24 | 0x312 0x315 0x318 0x31B +bpp | 640x480 800x600 1024x768 +----+--------------------------- + 16 | 0x311 0x314 0x317 + 24 | 0x312 0x315 0x318 + 32 | 0x329 0x32E 0x338 + +32-bit is really 8:8:8:8, but the final 8-bit number is an "empty" +alpha channel, it's otherwise equal to 24-bit color. However, they +could still be useful. For example, "fbterm" supports 32-bit mode +but not 24-bit mode. + +Notes about Modesetting +======================== + +The modesetting code in sm712fb has major problems. + +* Switching to 8-bit color mode will result in a black screen, so +they are removed from the list of supported graphic modes. But they +can still be switched to on-the-fly, don't do that then! + +* Only a refresh rate of 60 Hz is supported. + +* 1024x768 with 16-bit color is not really supported, because the +registers have been hacked by the original developer to adapt +the 1024x600 screen on Lemote YeeLoong 8089. + +* If you are using a Lemote YeeLoong 8089, please remember that only +the 1024x768 modes are guaranteed to drive the LCD panel properly. +Other modes are meant to drive a CRT, and may drive the LCD incorrectly +and result in a white screen with random garbage. External VGA output is +unaffected. + +Due to the way registers are hardcoded, it's impossible to fix them +without a major code rewrite. If you've been hit by these problems badly +and really need to get them fixed, please contact the driver maintainers. + +2D acceleration +============== + +Without 2D acceleration, the framebuffer suffers from extremely low performance, +even scrolling a single line of text on the console required an unaccelerated +screen redraw. Thus, 2D acceleration is enable by default. However, currently +it's only supported on SM710/712 with Little-Endian CPUs. Big-endian and +SM720 devices are currently not supported. + +2D acceleration can be controlled using the `video=sm712fb:accel:1` parameter. +The default option, "1" activate 2D acceleration. If you have problems, you can +set "0" to disable it. Different options can be separated by a comma, for +example, "video=sm712fb:0x31B,accel:0" set the resolution to 1280x1024x24bpp +while disabling the 2D acceleration. + +Although it has been extensively tested by the maintainer, 2D acceleration +in 24-bit color mode may still have minor issues. If you've encounter any +screen glitches in 24-bit mode in Linux framebuffer the framebuffer, don't +hurry disabling it, you should try switching to 32-bit mode first, normally +it should fix the problem. If you can reliably reproduce the screen glitches, +please report your method to the maintainers. Missing Features ================ (alias TODO list) - * 2D acceleratrion +The following features are not implemented in this driver, + + * 2D acceleration on SM720 and Big-Endian CPUs. + * More VGA modes. * dual-head support + * hardware cursor support + +The first feature is planned to be implemented soon, but the maintainer +does not receive any monetary or hardware support from any company or OEMs, +and he has to purchase a test platform personally. The 1998's hardware +still costs 200 USD+, so don't expected an ETA. If you have a Big-Endian +platform and willing to help testing, please contact the maintainer, thanks! + +Other VGA modes, dual-head, or hardware cursor support should be possible to +implement, but parts of the code must be rewritten, and there's little demand +for them on this legacy (retro?) platform, so there's no plan to implement them. +If you have a genuine need for them, please contact the maintainers. + +Maintainers +================ + +This driver is maintained by + + * Tom Li + * Sudip Mukherjee + * Teddy Wang + +Tom Li was the last contributor of this driver who implemented 2D acceleration, +and is the main author of this documentation, please send any bug reports or +requests to Tom, but don't forget to CC other maintainers as well to make everyone +be informed.