From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.4]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B6D4738B15E; Mon, 3 Aug 2026 18:41:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.4 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785782480; cv=none; b=iUhHd08gUmwi/v/RWd+y02tuJTrB1cMIAcG0ibrOG47BBB4fcs5zeW9SuYyLZue99toSm2pY3Wst63FCfu9FcK5j+1g5TAuVHXmFA2aGGwyTO1iBYrMIJlUIIIwjgqWxYrwxO5JClBxS2C3fUaUl+Nld+TbLcPiwOupVrZkwTe0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785782480; c=relaxed/simple; bh=MqV62ckTjykRVWX+ntN54Ek77uIGz8UuiFcKI+vRvnk=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=YErpfR0gKKXet+lEPraYfnxlpYOvy9JMd+EfEWZGYNMyXM+5qPn+vy2DC9wNK10DdEKaqUqsckp6Qt9TlXZAJ4/14Xhv1+gHMOyZMtcQsWLVq/m4TMEL07uWJGewDTgU/Dh6FngufqQ2G+mdPFvVy7pdf2RMOPImj96VF2cFOdY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=p1qiwWrI; arc=none smtp.client-ip=220.197.31.4 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="p1qiwWrI" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=cz TzwkOup/amQBLx5Tqq0ySvbnAWhyNs36XA7D0LTx0=; b=p1qiwWrI2nO8dYxXdj xiQnXLyn5jXkZviNBmNQ9N5TayS02tUDib1USVqr6GHjpzFQYLUIIjI9nvUGyh8C uI9BE26DgsE0S8wC+/1uE3F4Nvx2hLA6wAB4loZ8jQ6mYwrNVWic1jARMHzviSgc IncbHD8CODeyXTFr+laF6DyV8= Received: from localhost (unknown []) by gzga-smtp-mtada-g0-4 (Coremail) with SMTP id _____wAnoEuP4HBqSZOVNg--.52543S2; Tue, 04 Aug 2026 02:40:16 +0800 (CST) From: sh_def@163.com To: Helge Deller , linux-fbdev@vger.kernel.org Cc: Hui Su , =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= , Abdun Nihaal , Maxime Ripard , Tomi Valkeinen , Andrew Morton , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH] fbdev: ssd1307fb: defer I2C transfers from damage callbacks Date: Tue, 4 Aug 2026 02:39:57 +0800 Message-ID: <20260803183957.3481000-1-sh_def@163.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:_____wAnoEuP4HBqSZOVNg--.52543S2 X-Coremail-Antispam: 1Uf129KBjvJXoW3GF4UZr1fGr18uw45Aw47Jwb_yoWfuFyxpF yYqFyfAr4vga109rs3CFsrAryF9a93tr9Fkry3K3WxAFy7twnrur1v9r95ZrWDGrZ8Jrn7 ur9Yqw18Gr4UXFJanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0pESoGDUUUUU= X-CM-SenderInfo: xvkbvvri6rljoofrz/xtbCwRATcmpw4JBfpQAA3g From: Hui Su The fbdev damage callbacks may run from fbcon while printk has disabled preemption. They currently update the display synchronously, which enters the sleeping I2C transfer path from atomic context. A complete report from an RK3566 system follows: [ 258.129004] watchdog: watchdog0: watchdog did not stop! [ 258.129067] BUG: scheduling while atomic: systemd/1/0x00000003 [ 258.129076] Modules linked in: algif_hash algif_skcipher af_alg bnep binfmt_misc lz4hc lz4 zram snd_soc_hdmi_codec brcmfmac_wcc hci_uart fb_ssd1306(C) fbtft(C) btqca btrtl btintel btsdio snd_soc_simple_card motorcomm pwm_fan snd_soc_simple_card_utils ssd130x_spi nls_iso8859_1 ssd130x btbcm drm_shmem_helper display_connector brcmfmac ssd1307fb brcmutil bluetooth cfg80211 rfkill snd_soc_rockchip_i2s_tdm snd_soc_rk817 hantro_vpu snd_soc_core snd_compress snd_pcm_dmaengine v4l2_vp9 snd_pcm v4l2_h264 rockchip_rga snd_timer rk_crypto2 spi_rockchip_sfc videobuf2_dma_contig snd sm3_generic v4l2_mem2mem videobuf2_dma_sg dwmac_rk sm3 soundcore videobuf2_memops videobuf2_v4l2 stmmac_platform dw_hdmi_cec videodev videobuf2_common dw_hdmi_i2s_audio stmmac rk817_charger pcs_xpcs mc cpufreq_dt sch_fq_codel ip_tables x_tables autofs4 [ 258.129215] Preemption disabled at: [ 258.129216] [] vprintk_emit+0x11c/0x340 [ 258.129234] CPU: 0 PID: 1 Comm: systemd Tainted: G C 6.6.0-rc5-rockchip-rk356x #4 [ 258.129239] Hardware name: Rockchip RK3566 OPi 3B (DT) [ 258.129243] Call trace: [ 258.129245] dump_backtrace+0xa0/0x128 [ 258.129252] show_stack+0x20/0x38 [ 258.129256] dump_stack_lvl+0x60/0xb0 [ 258.129265] dump_stack+0x18/0x28 [ 258.129269] __schedule_bug+0xa0/0xc8 [ 258.129274] __schedule+0x9ac/0xd30 [ 258.129279] schedule+0x60/0x100 [ 258.129282] schedule_timeout+0x194/0x338 [ 258.129289] rk3x_i2c_xfer_common.isra.0+0x384/0x498 [ 258.129296] rk3x_i2c_xfer+0x20/0x60 [ 258.129300] __i2c_transfer+0x194/0x648 [ 258.129308] i2c_transfer+0x9c/0x130 [ 258.129313] i2c_transfer_buffer_flags+0x64/0x98 [ 258.129318] ssd1307fb_update_rect+0x42c/0x560 [ssd1307fb] [ 258.129334] ssd1307fb_defio_imageblit+0x34/0x50 [ssd1307fb] [ 258.129343] soft_cursor+0x13c/0x210 [ 258.129350] bit_cursor+0x2dc/0x550 [ 258.129354] fbcon_cursor+0xec/0x108 [ 258.129359] hide_cursor+0x44/0xc8 [ 258.129365] vt_console_print+0x398/0x3b0 [ 258.129370] console_flush_all.isra.0+0x17c/0x410 [ 258.129377] console_unlock+0x4c/0x100 [ 258.129382] vprintk_emit+0x1c8/0x340 [ 258.129386] vprintk_default+0x40/0x58 [ 258.129389] vprintk+0xb8/0xd0 [ 258.129392] _printk+0x68/0x98 [ 258.129398] watchdog_release+0x170/0x230 [ 258.129404] __fput+0xbc/0x288 [ 258.129409] __fput_sync+0x58/0x70 [ 258.129413] __arm64_sys_close+0x40/0x90 [ 258.129419] invoke_syscall+0x4c/0x118 [ 258.129426] el0_svc_common.constprop.0+0x48/0xf0 [ 258.129432] do_el0_svc+0x24/0x38 [ 258.129437] el0_svc+0x48/0x100 [ 258.129443] el0t_64_sync_handler+0xc0/0xc8 [ 258.129448] el0t_64_sync+0x190/0x198 [ 258.573087] ------------[ cut here ]------------ [ 258.573098] DEBUG_LOCKS_WARN_ON(val > preempt_count()) [ 258.573111] WARNING: CPU: 0 PID: 1 at kernel/sched/core.c:5871 preempt_count_sub+0x9c/0x148 [ 258.573130] Modules linked in: algif_hash algif_skcipher af_alg bnep binfmt_misc lz4hc lz4 zram snd_soc_hdmi_codec brcmfmac_wcc hci_uart fb_ssd1306(C) fbtft(C) btqca btrtl btintel btsdio snd_soc_simple_card motorcomm pwm_fan snd_soc_simple_card_utils ssd130x_spi nls_iso8859_1 ssd130x btbcm drm_shmem_helper display_connector brcmfmac ssd1307fb brcmutil bluetooth cfg80211 rfkill snd_soc_rockchip_i2s_tdm snd_soc_rk817 hantro_vpu snd_soc_core snd_compress snd_pcm_dmaengine v4l2_vp9 snd_pcm v4l2_h264 rockchip_rga snd_timer rk_crypto2 spi_rockchip_sfc videobuf2_dma_contig snd sm3_generic v4l2_mem2mem videobuf2_dma_sg dwmac_rk sm3 soundcore videobuf2_memops videobuf2_v4l2 stmmac_platform dw_hdmi_cec videodev videobuf2_common dw_hdmi_i2s_audio stmmac rk817_charger pcs_xpcs mc cpufreq_dt sch_fq_codel ip_tables x_tables autofs4 [ 258.573268] CPU: 0 PID: 1 Comm: systemd Tainted: G WC 6.6.0-rc5-rockchip-rk356x #4 [ 258.573274] Hardware name: Rockchip RK3566 OPi 3B (DT) ** 37 printk messages dropped ** [ 258.574064] Preemption disabled at: ** 42 printk messages dropped ** [ 259.190237] Preemption disabled at: Track damage in the driver's private data under a spinlock and merge multiple updates into a bounding rectangle. Queue the existing deferred-I/O work immediately for damage reported by fbdev drawing and write helpers, so allocation and I2C transfers run from process context without adding the configured mmap refresh delay. Keep full-screen updates for dirty mmap pages, for which no precise rectangle is available. Tested on an RK3566 board with a 128x64 OLED by running five rounds of 250 KERN_EMERG messages in total while issuing framebuffer writes every 15 ms. No atomic-sleep, preemption, or lockdep warning occurred. Kprobe tracing also confirmed that cursor-only damage remained an 8x16 partial update. Fixes: a2ed00da5047 ("drivers/video: add support for the Solomon SSD1307 OLED Controller") Cc: stable@vger.kernel.org Signed-off-by: Hui Su --- drivers/video/fbdev/ssd1307fb.c | 72 ++++++++++++++++++++++++++++++--- 1 file changed, 67 insertions(+), 5 deletions(-) diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c index 644b8d97b381..c4fdecafd856 100644 --- a/drivers/video/fbdev/ssd1307fb.c +++ b/drivers/video/fbdev/ssd1307fb.c @@ -14,6 +14,7 @@ #include #include #include +#include #include #include @@ -72,6 +73,13 @@ struct ssd1307fb_par { struct i2c_client *client; u32 height; struct fb_info *info; + /* Pending damage, with exclusive x2/y2, protected by damage_lock. */ + spinlock_t damage_lock; + bool damage_pending; + u32 damage_x1; + u32 damage_x2; + u32 damage_y1; + u32 damage_y2; u8 lookup_table[4]; u32 page_offset; u32 col_offset; @@ -302,19 +310,49 @@ static int ssd1307fb_blank(int blank_mode, struct fb_info *info) return ssd1307fb_write_cmd(par->client, SSD1307FB_DISPLAY_ON); } +static void ssd1307fb_schedule_damage(struct fb_info *info, u32 x, u32 y, + u32 width, u32 height) +{ + struct ssd1307fb_par *par = info->par; + unsigned long flags; + u32 x2, y2; + + if (!width || !height || x >= par->width || y >= par->height) + return; + + x2 = x + min(width, par->width - x); + y2 = y + min(height, par->height - y); + + spin_lock_irqsave(&par->damage_lock, flags); + if (par->damage_pending) { + par->damage_x1 = min(par->damage_x1, x); + par->damage_y1 = min(par->damage_y1, y); + par->damage_x2 = max(par->damage_x2, x2); + par->damage_y2 = max(par->damage_y2, y2); + } else { + par->damage_x1 = x; + par->damage_y1 = y; + par->damage_x2 = x2; + par->damage_y2 = y2; + par->damage_pending = true; + } + spin_unlock_irqrestore(&par->damage_lock, flags); + + /* Advance an already-pending mmap update as well. */ + mod_delayed_work(system_wq, &info->deferred_work, 0); +} + static void ssd1307fb_defio_damage_range(struct fb_info *info, off_t off, size_t len) { struct ssd1307fb_par *par = info->par; - ssd1307fb_update_display(par); + ssd1307fb_schedule_damage(info, 0, 0, par->width, par->height); } static void ssd1307fb_defio_damage_area(struct fb_info *info, u32 x, u32 y, u32 width, u32 height) { - struct ssd1307fb_par *par = info->par; - - ssd1307fb_update_rect(par, x, y, width, height); + ssd1307fb_schedule_damage(info, x, y, width, height); } FB_GEN_DEFAULT_DEFERRED_SYSMEM_OPS(ssd1307fb, @@ -329,7 +367,30 @@ static const struct fb_ops ssd1307fb_ops = { static void ssd1307fb_deferred_io(struct fb_info *info, struct list_head *pagereflist) { - ssd1307fb_update_display(info->par); + struct ssd1307fb_par *par = info->par; + unsigned long flags; + u32 x, y, width, height; + + spin_lock_irqsave(&par->damage_lock, flags); + if (!list_empty(pagereflist)) { + x = 0; + y = 0; + width = par->width; + height = par->height; + par->damage_pending = false; + } else if (par->damage_pending) { + x = par->damage_x1; + y = par->damage_y1; + width = par->damage_x2 - par->damage_x1; + height = par->damage_y2 - par->damage_y1; + par->damage_pending = false; + } else { + spin_unlock_irqrestore(&par->damage_lock, flags); + return; + } + spin_unlock_irqrestore(&par->damage_lock, flags); + + ssd1307fb_update_rect(par, x, y, width, height); } static int ssd1307fb_init(struct ssd1307fb_par *par) @@ -601,6 +662,7 @@ static int ssd1307fb_probe(struct i2c_client *client) par = info->par; par->info = info; par->client = client; + spin_lock_init(&par->damage_lock); par->device_info = device_get_match_data(dev); base-commit: 075b74841bd0065a3bda3440873c747938e69b68 -- 2.43.0