Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756517AbdCWRib (ORCPT ); Thu, 23 Mar 2017 13:38:31 -0400 Received: from bny206.haproxy.com ([37.58.153.206]:53046 "EHLO smtp.exceliance.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755341AbdCWRi3 (ORCPT ); Thu, 23 Mar 2017 13:38:29 -0400 Date: Thu, 23 Mar 2017 18:15:01 +0100 From: Willy TARREAU To: Geert Uytterhoeven Cc: Miguel Ojeda Sandonis , Greg Kroah-Hartman , Ksenija Stanojevic , Arnd Bergmann , linux-kernel@vger.kernel.org Subject: Re: [PATCH 00/13] Add HD44780 Character LCD support Message-ID: <20170323171501.GI9408@haproxy.com> References: <1486391895-9554-1-git-send-email-geert@linux-m68k.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1486391895-9554-1-git-send-email-geert@linux-m68k.org> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5058 Lines: 111 Hi Geert, On Mon, Feb 06, 2017 at 03:38:02PM +0100, Geert Uytterhoeven wrote: > Hi all, > > Character LCDs are currently typically driven from userspace, either > directly through bit-banging, or via some kind of serial (UART/i2c) > interface. > > This patch series adds kernel support for character LCDs using an > Hitachi HD44780 Character LCD Controller where its M6800 bus interface > is connected to GPIOs. It does so after extracting the character LCD > core support from the existing Parallel port LCD/Keypad Panel driver > into its own subdriver. > > - Patch 1 fixes a bug in the existing panel driver, > - Patches 2-8 perform clean ups and improvements to the panel driver, > - Patch 9 extract the character LCD core support from the panel driver > into an auxdisplay charlcd subdriver, > - Patches 10-11 add new features to the character LCD core driver > (4-bit interface support and support for displays with more than 2 > lines), > - Patch 12 adds DT bindings for describing HD44780 Character LCDs, > - Patch 13 adds a driver for HD44780 Character LCDs connected to > GPIOs, using the new character LCD core. > > Note that Linux has other support for HD44780 Character LCDs, but none of > it is generic: > - drivers/misc/arm-charlcd.c involves a custom IP block for interfacing > to the LCD controller, > - drivers/parisc/led.c is tightly coupled to LED handling on various HP > PA-RISC machines. > > This has been tested using a 20x4 character LCD with backlight, using both > 8-bit and 4-bit wiring to one or two 74HC595 shift registers connected to > an SPI master controller. > > Regression testing on original "panel" hardware would be appreciated. So I finally had the time to give it a try by applying your patchset on top of our 4.9 prod kernel. For now I'm getting a panic at boot : BUG: unable to handle kernel NULL pointer dereference at (null) IP: [] __mutex_lock_slowpath+0x6d/0x100 PGD 0 Oops: 0002 [#1] SMP Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.9.0-alb90.0-alb3100-lcdtest #3 Hardware name: To Be Filled By Intel To Be Filled By Intel/To be filled by Intel, BIOS 080015 04/01/2011 task: ffff88007c488000 task.stack: ffff88007c490000 RIP: 0010:[] [] __mutex_lock_slowpath+0x6d/0x100 RSP: 0000:ffff88007c493cc8 EFLAGS: 00010282 RAX: 0000000000000000 RBX: ffff88007c5a0f90 RCX: ffff88007c48d700 RDX: ffff88007c493cd0 RSI: 0000000000000000 RDI: ffff88007c5a0f94 RBP: ffff88007c488000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000002ea48c3 R12: ffff88007c5a0f94 R13: 00000000ffffffff R14: ffff88007c5a0f98 R15: ffff88007c470000 FS: 0000000000000000(0000) GS:ffff88007ee00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000001607000 CR4: 00000000000006f0 Stack: ffff88007ee0ea80 ffff88007c5a0f98 0000000000000000 0000000000000282 ffff88007c5a0f90 ffff88007c5a0f90 0000000000000000 ffff88007c493f28 ffff88007c493f28 ffffffff813e20de ffff88007c5a0f00 ffffffff812a9cc3 Call Trace: [] ? mutex_lock+0xe/0x20 [] ? charlcd_backlight+0x33/0x80 [] ? lcd_write_data_p8+0x80/0x80 [] ? charlcd_init_display+0x135/0x1a0 [] ? charlcd_register+0xf/0xf0 [] ? panel_attach+0x4c8/0x9c0 [] ? attach_driver_chain+0x60/0x60 [] ? port_check+0x1b/0x30 [] ? bus_for_each_dev+0x4f/0x80 [] ? __parport_register_driver+0x112/0x150 [] ? loop_init+0x11d/0x13c [] ? loop_init+0x13c/0x13c [] ? panel_init_module+0x1b9/0x20a [] ? do_one_initcall+0x42/0x160 [] ? kernel_init_freeable+0x10e/0x1d8 [] ? loglevel+0x36/0x36 [] ? rest_init+0x70/0x70 [] ? kernel_init+0xa/0x100 [] ? rest_init+0x70/0x70 [] ? ret_from_fork+0x22/0x30 Code: 03 83 f8 01 0f 84 9d 00 00 00 48 8b 43 10 48 8d 54 24 08 4c 8d 73 08 48 89 53 10 4c 89 74 24 08 48 89 44 24 10 41 bd ff ff ff ff <48> 89 10 48 89 6c 24 18 eb 1a 48 c7 45 08 02 00 00 00 c6 43 04 RIP [] __mutex_lock_slowpath+0x6d/0x100 RSP CR2: 0000000000000000 ---[ end trace e58465f0f36b5a27 ]--- Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 I suspect that's related to the backlight timer though I'm not sure. In case that helps I'm using the following config : $ grep 'PANEL\|LCD' .config CONFIG_PANEL=y CONFIG_PANEL_PARPORT=0 CONFIG_PANEL_PROFILE=4 CONFIG_PANEL_CHANGE_MESSAGE=y CONFIG_PANEL_BOOT_MESSAGE="ALOHA ALB3100" # CONFIG_BACKLIGHT_LCD_SUPPORT is not set # CONFIG_HID_PICOLCD is not set # CONFIG_USB_LCD is not set CONFIG_CHARLCD=y I'm going to comment out the backlight code to see if it improves the situation. Cheers, Willy