linux-kernel - [PATCH 1/3] fbdev: omap: use threaded IRQ for LCD DMA

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Message-ID: <20250102181953.1020878-2-aaro.koskinen@iki.fi>
Date: Thu,  2 Jan 2025 20:19:51 +0200
From: Aaro Koskinen <aaro.koskinen@....fi>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Helge Deller <deller@....de>,
	Janusz Krzysztofik <jmkrzyszt@...il.com>,
	Tony Lindgren <tony@...mide.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-fbdev@...r.kernel.org,
	linux-omap@...r.kernel.org,
	linux-input@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Aaro Koskinen <aaro.koskinen@....fi>
Subject: [PATCH 1/3] fbdev: omap: use threaded IRQ for LCD DMA

When using touchscreen and framebuffer, Nokia 770 crashes easily with:

    BUG: scheduling while atomic: irq/144-ads7846/82/0x00010000
    Modules linked in: usb_f_ecm g_ether usb_f_rndis u_ether libcomposite configfs omap_udc ohci_omap ohci_hcd
    CPU: 0 UID: 0 PID: 82 Comm: irq/144-ads7846 Not tainted 6.12.7-770 #2
    Hardware name: Nokia 770
    Call trace:
     unwind_backtrace from show_stack+0x10/0x14
     show_stack from dump_stack_lvl+0x54/0x5c
     dump_stack_lvl from __schedule_bug+0x50/0x70
     __schedule_bug from __schedule+0x4d4/0x5bc
     __schedule from schedule+0x34/0xa0
     schedule from schedule_preempt_disabled+0xc/0x10
     schedule_preempt_disabled from __mutex_lock.constprop.0+0x218/0x3b4
     __mutex_lock.constprop.0 from clk_prepare_lock+0x38/0xe4
     clk_prepare_lock from clk_set_rate+0x18/0x154
     clk_set_rate from sossi_read_data+0x4c/0x168
     sossi_read_data from hwa742_read_reg+0x5c/0x8c
     hwa742_read_reg from send_frame_handler+0xfc/0x300
     send_frame_handler from process_pending_requests+0x74/0xd0
     process_pending_requests from lcd_dma_irq_handler+0x50/0x74
     lcd_dma_irq_handler from __handle_irq_event_percpu+0x44/0x130
     __handle_irq_event_percpu from handle_irq_event+0x28/0x68
     handle_irq_event from handle_level_irq+0x9c/0x170
     handle_level_irq from generic_handle_domain_irq+0x2c/0x3c
     generic_handle_domain_irq from omap1_handle_irq+0x40/0x8c
     omap1_handle_irq from generic_handle_arch_irq+0x28/0x3c
     generic_handle_arch_irq from call_with_stack+0x1c/0x24
     call_with_stack from __irq_svc+0x94/0xa8
    Exception stack(0xc5255da0 to 0xc5255de8)
    5da0: 00000001 c22fc620 00000000 00000000 c08384a8 c106fc00 00000000 c240c248
    5dc0: c113a600 c3f6ec30 00000001 00000000 c22fc620 c5255df0 c22fc620 c0279a94
    5de0: 60000013 ffffffff
     __irq_svc from clk_prepare_lock+0x4c/0xe4
     clk_prepare_lock from clk_get_rate+0x10/0x74
     clk_get_rate from uwire_setup_transfer+0x40/0x180
     uwire_setup_transfer from spi_bitbang_transfer_one+0x2c/0x9c
     spi_bitbang_transfer_one from spi_transfer_one_message+0x2d0/0x664
     spi_transfer_one_message from __spi_pump_transfer_message+0x29c/0x498
     __spi_pump_transfer_message from __spi_sync+0x1f8/0x2e8
     __spi_sync from spi_sync+0x24/0x40
     spi_sync from ads7846_halfd_read_state+0x5c/0x1c0
     ads7846_halfd_read_state from ads7846_irq+0x58/0x348
     ads7846_irq from irq_thread_fn+0x1c/0x78
     irq_thread_fn from irq_thread+0x120/0x228
     irq_thread from kthread+0xc8/0xe8
     kthread from ret_from_fork+0x14/0x28

As a quick fix, switch to a threaded IRQ which provides a stable system.

Signed-off-by: Aaro Koskinen <aaro.koskinen@....fi>
---
 drivers/video/fbdev/omap/lcd_dma.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/video/fbdev/omap/lcd_dma.c b/drivers/video/fbdev/omap/lcd_dma.c
index f85817635a8c..0da23c57e475 100644
--- a/drivers/video/fbdev/omap/lcd_dma.c
+++ b/drivers/video/fbdev/omap/lcd_dma.c
@@ -432,8 +432,8 @@ static int __init omap_init_lcd_dma(void)
 
 	spin_lock_init(&lcd_dma.lock);
 
-	r = request_irq(INT_DMA_LCD, lcd_dma_irq_handler, 0,
-			"LCD DMA", NULL);
+	r = request_threaded_irq(INT_DMA_LCD, NULL, lcd_dma_irq_handler,
+				 IRQF_ONESHOT, "LCD DMA", NULL);
 	if (r != 0)
 		pr_err("unable to request IRQ for LCD DMA (error %d)\n", r);
 
-- 
2.39.2