Re: [PATCH V2 2/3] dmaselftest: add memcpy selftest support functions

From: Sinan Kaya
Date: Wed Nov 04 2015 - 21:42:55 EST

On 11/3/2015 11:08 AM, Vinod Koul wrote:
On Tue, Nov 03, 2015 at 10:22:25AM +0200, Andy Shevchenko wrote:
On Tue, Nov 3, 2015 at 9:44 AM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
On Mon, Nov 2, 2015 at 10:30 PM, Vinod Koul <vinod.koul@xxxxxxxxx> wrote:
On Mon, Nov 02, 2015 at 11:18:37PM -0500, Sinan Kaya wrote:
On 11/2/2015 11:15 PM, Vinod Koul wrote:
On Mon, Nov 02, 2015 at 01:07:38AM -0500, Sinan Kaya wrote:

This one; on the other hand, is selftest to verify hardware is
working as expected during power up.

I prefer to have such nice case by run time parameter (let's say
common to all DMA Engine drivers)

We can have common code which is used for dmatest as well as selftest. I do
not want to see same code duplicated..

First thought was to merge this to dmatest, however, some DMA
controllers doesn't have a memcpy capability.

The tests should be based on capablity of memcpy

How would we test them?

Here is what I proposed.

- a common file that gets compiled into a module that wants to use self-test with a public API. It can be called from driver's probe routine.
- the test is independent of my implementation. It uses dmaengine API and should be portable to most drivers.
- there *are* still drivers in the kernel that has selftest code embedded inside them. I followed the design pattern from other drivers thinking this must have been a good idea and it paid off for me.

As far as I understand, there is interest in doing more than this and reusing the dmatest code for code duplication.

- Dmatest can be actually configured to run during boot.
- Nobody besides the dma driver developer uses dmatest. This leaves holes for regressions that are really hard to debug due to interaction with the rest of the system.
- Dmatest doesn't exist in most distribution kernels.

If we want to do something else, I need clear directions. I can remove the self test code completely from my driver. But, I need an equivalent functionality.

> That part is tricky, you need to do so thru clients, spi/audio/serial etc

My selftest code actually attaches to all slave devices and issues a memcpy command and then detaches from the slave devices.

Sinan Kaya
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
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