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From: Raimonds Cicans <ray@apollo.lv>
To: linux-media@vger.kernel.org
Subject: cx23885: risc op code error - strange solution...
Date: Thu, 17 Jun 2021 23:30:12 +0300	[thread overview]
Message-ID: <5f01f85e-a8a0-4d79-d7a3-d32d9e4888a5@apollo.lv> (raw)

[-- Attachment #1: Type: text/plain, Size: 645 bytes --]

Hi!

Yet again I try to fight cx23885 driver's "risc op code error" bug.

I found very weird "fix":
If I apply attached patch _AND_ enable KASAN, then problem disappear.
If I disable KASAN or delete _ANY_ new line from patch, then problem 
reappear.

I tried to replace "printk" with delays and with memory barriers, but 
nothing works.

I would like to hear from community any ideas:
1. why this "fix" helps
2. what weird things "printk" can do when KASAN enabled
3. why we need two consecutive "cx23885_irq_get_mask(dev);" commands, 
first of which need strange "companions"
4. what else I can try to use instead of "printk"


Raimonds Cicans

[-- Attachment #2: cx23885-core_risc_KASAN.patch --]
[-- Type: text/x-patch, Size: 438 bytes --]

--- /usr/src/linux-5.10.27-gentoo__orig/drivers/media/pci/cx23885/cx23885-core.c	2021-04-03 09:20:56.609971911 +0300
+++ /usr/src/linux-5.10.27-gentoo/drivers/media/pci/cx23885/cx23885-core.c	2021-06-17 22:34:49.503333355 +0300
@@ -1517,6 +1517,10 @@
 	if (debug > 4)
 		cx23885_tsport_reg_dump(port);
 
+	printk(KERN_INFO);
+	cx23885_irq_get_mask(dev);
+	printk(KERN_INFO);
+
 	cx23885_irq_get_mask(dev);
 
 	/* clear dma in progress */

                 reply	other threads:[~2021-06-17 20:40 UTC|newest]

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