linux-kernel - Re: [PATCH 01/10] spi: dw: Add support for polled operation via no IRQ specified in DT

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Message-ID: <874kshpnor.fsf@soft-dev15.microsemi.net>
Date:   Fri, 15 May 2020 11:11:48 +0200
From:   Lars Povlsen <lars.povlsen@...rochip.com>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
CC:     Mark Brown <broonie@...nel.org>,
        Serge Semin <fancer.lancer@...il.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        SoC Team <soc@...nel.org>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        <linux-spi@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH 01/10] spi: dw: Add support for polled operation via no IRQ specified in DT


Serge Semin writes:

> Hi Mark
>
> On Wed, May 13, 2020 at 03:20:50PM +0100, Mark Brown wrote:
>> On Wed, May 13, 2020 at 04:00:22PM +0200, Lars Povlsen wrote:
>> > With this change a SPI controller can be added without having a IRQ
>> > associated, and causing all transfers to be polled. For SPI controllers
>> > without DMA, this can significantly improve performance by less
>> > interrupt handling overhead.
>>
>> This overlaps substantially with some work that Serge Semin (CCed) has
>> in progress, please coordinate with him.
>
> Thanks for copying me these mails. I haven't been Cc'ed in the series and
> hasn't been subscribed to the SPI mailing list, so I would have definitely
> missed that.
>
> I would like to coordinate my efforts with Lars. I'll have the patchset reviewed
> soon in addition providing my comments/suggestions of how to make it useful for
> both mine and Lars solution.

Serge - thanks for taking on this.

Note that my primary concern now is to get Sparx5 upstreamed. The
mem_ops (or dirmap) and polled mode are both performance enhancements,
which can be pulled from my series if it creates too much noise. I can
then add the necessary on top of your work/current kernel at a later
time.

> One thing I can tell about the mem_ops he implemented, is that they aren't
> mem_ops, but dirmap (as you remember it's also implemented in my code, but with
> alignment specific), and the exec_mem_op partly consists of a code, which belong
> to the supports_op() callback. The rest of my comments will be inlined in the
> patches.
>
> -Sergey

-- 
Lars Povlsen,
Microchip