Re: [PATCH v2 1/8] mmc: sdhci: Get rid of finish_tasklet

Faiz Abbas
2019-04-02T07:59:10Z

Hi Adrian,

On 26/03/19 1:03 PM, Adrian Hunter wrote:
> On 18/03/19 11:33 AM, Ulf Hansson wrote:
>> + Arnd, Grygorii
>>
>> On Fri, 15 Feb 2019 at 20:17, Faiz Abbas <faiz_abbas@ti.com> wrote:
>>>
>>> sdhci.c has two bottom halves implemented. A threaded_irq for handling
>>> card insert/remove operations and a tasklet for finishing mmc requests.
>>> With the addition of external dma support, dmaengine APIs need to
>>> terminate in non-atomic context before unmapping the dma buffers.
>>>
>>> To facilitate this, remove the finish_tasklet and move the call of
>>> sdhci_request_done() to the threaded_irq() callback. Also move the
>>> interrupt result variable to sdhci_host so it can be populated from
>>> anywhere inside the sdhci_irq handler.
>>>
>>> Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
>>
>> Adrian, I think it makes sense to apply this patch, even if there is
>> very minor negative impact throughput wise.
>>
>> To me, it doesn't seems like MMC/SD/SDIO has good justification for
>> using tasklets, besides from the legacy point of view, of course.
>> Instead, I think we should try to move all mmc hosts into using
>> threaded IRQs.
>>
>> So, what do you think? Can you overlook the throughput drop and
>> instead we can try to recover this on top with other optimizations?
>
> I tend to favour good results as expressed here:
>
> https://lkml.org/lkml/2007/6/22/360
>
> So I want to do optimization first.
>
> But performance is not the only problem with the patch. Give me a few
> days and I will see what I can come up with.
>

Gentle ping on this.

Thanks,
Faiz