Re: [PATCH] fbdev: ssd1307fb: defer I2C transfers from damage callbacks

On 8/3/26 20:39, [email protected] wrote:
> From: Hui Su <[email protected]>
> 
> 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] [<ffff80008012f96c>] 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: [email protected]
> Signed-off-by: Hui Su <[email protected]>
> ---
>   drivers/video/fbdev/ssd1307fb.c | 72 ++++++++++++++++++++++++++++++---
>   1 file changed, 67 insertions(+), 5 deletions(-)
applied.

Thanks!
Helge