On 08/07/2015 05:29 PM, Russell King - ARM Linux wrote:
> On Fri, Aug 07, 2015 at 11:08:48AM -0400, Peter Hurley wrote:
>> [ + Greg KH ]
>>
>> On 08/07/2015 09:57 AM, Russell King - ARM Linux wrote:
>>> As it is something that the driver has _not_ supported, you are clearly
>>> adding a feature to an existing driver. It's not a bug fix.
>>>
>>>>> If something else has been converted to pause channels and that is causing
>>>>> a problem, then _that_ conversion is where the bug lies, not the lack of
>>>>> support in the omap-dma.
>>
>> FWIW, the actual bug is the api that silently does nothing.
>
> Incorrect.
>
> static int omap_dma_pause(struct dma_chan *chan)
> {
> struct omap_chan *c = to_omap_dma_chan(chan);
>
> /* Pause/Resume only allowed with cyclic mode */
> if (!c->cyclic)
> return -EINVAL;
>
> Asking for the channel to be paused will return an error code indicating
> that the request failed. That will be propagated back through to the
> return code of dmaengine_pause().
>
> If we look at what 8250-dma.c is doing:
>
> if (dma->rx_running) {
> dmaengine_pause(dma->rxchan);
>
> It's 8250-dma.c which is silently _ignoring_ the return code, failing
> to check that the operation it requested worked. Maybe this should be
> WARN_ON(dmaengine_pause(dma->rxchan)) or at least it should print a
> message?
I think this is what Peter meant by saying "silently does nothing".
> So, I guess that means that older kernels will just have to remain broken -
> all because the basic testing of the original code was never undertaken
> to ensure that basic stuff like reception of characters worked properly.
Hehe. I wouldn't describe testing at 3mbaud as basic. This reads as I
didn't do any kind of testing at all prior submitting the driver. This
was not the case.
Sebastian
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