CODEWITHSUNDEEP
cprintfspiomapisr
Nikhil Chaubey
Nikhil Chaubey

Reputation: 1

Spi interrupt handler works when a printf() is used

I am trying to initiate a spi communication between an omap processor an sam4l one. I have configured spi protocol and omap is the master. Now what I see is the test data I am sending is correctly reaching on sam4l and I can see the isr is printing that data. Using more printf here and there in isr makes the operation happen and the respective operation happens, but if I remove all printfs I can't see any operation happening. What can be the cause of this anomaly? Is it a usual case of wrong frequency settings or something? If code is needed I will post that too but its big. Thanks

Upvotes: 0

Views: 283

Answers (2)

Richard at ImageCraft
Richard at ImageCraft

Reputation: 665

If a routine works with printf "here and there" and not otherwise, almostcertainly the problem is that there are timing issues. As a trivial example, let's say you write to an SPI flash and then check its content. The flash memory write will take some times, so if you check immediately, the data would not be valid, but if you insert a printf call in between, it may have taken enough time that the read back is now valid.

Upvotes: 0

Ratnesh69
Ratnesh69

Reputation: 11

I think you are trying to print message in driver.

As printing message on console with slow down your driver, it may behave slowly and your driver work well.

Use pr_info() for debug and change setting to not come message on console by editing /proc/sys/kernel/printk to 4 4 1 7

-> It will store debug message in buffer.

-> Driver not slow down because of printing message on screen.

-> And you can see it by typing dmesg command later.

Then find orignal problem which may cause error.

Upvotes: 0

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