mainlining shenanigans
02b9aec592
When I have KASAN enabled on my kernel and I start stressing the
touchscreen my system tends to hang. The touchscreen is one of the
only things that does a lot of big i2c transfers and ends up hitting
the DMA paths in the geni i2c driver. It appears that KASAN adds
enough delay in my system to tickle a race condition in the DMA setup
code.
When the system hangs, I found that it was running the geni_i2c_irq()
over and over again. It had these:
m_stat = 0x04000080
rx_st = 0x30000011
dm_tx_st = 0x00000000
dm_rx_st = 0x00000000
dma = 0x00000001
Notably we're in DMA mode but are getting M_RX_IRQ_EN and
M_RX_FIFO_WATERMARK_EN over and over again.
Putting some traces in geni_i2c_rx_one_msg() showed that when we
failed we were getting to the start of geni_i2c_rx_one_msg() but were
never executing geni_se_rx_dma_prep().
I believe that the problem here is that we are starting the geni
command before we run geni_se_rx_dma_prep(). If a transfer makes it
far enough before we do that then we get into the state I have
observed. Let's change the order, which seems to work fine.
Although problems were seen on the RX path, code inspection suggests
that the TX should be changed too. Change it as well.
Fixes:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.