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From: Mark Brown <broonie@kernel.org>
To: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Serge Semin <fancer.lancer@gmail.com>,
	Linus Walleij <linus.walleij@stericsson.com>,
	Vinod Koul <vkoul@kernel.org>, Feng Tang <feng.tang@intel.com>,
	Grant Likely <grant.likely@secretlab.ca>,
	Alan Cox <alan@linux.intel.com>,
	Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru>,
	Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>,
	Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Paul Burton <paulburton@kernel.org>,
	Ralf Baechle <ralf@linux-mips.org>, Arnd Bergmann <arnd@arndb.de>,
	Rob Herring <robh+dt@kernel.org>,
	linux-mips@vger.kernel.org, devicetree@vger.kernel.org,
	Wan Ahmad Zainie <wan.ahmad.zainie.wan.mohamad@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jarkko Nikula <jarkko.nikula@linux.intel.com>,
	"wuxu.wu" <wuxu.wu@huawei.com>, Clement Leger <cleger@kalray.eu>,
	Linus Walleij <linus.walleij@linaro.org>,
	linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 01/16] spi: dw: Add Tx/Rx finish wait methods to the MID DMA
Date: Fri, 22 May 2020 13:10:23 +0100	[thread overview]
Message-ID: <20200522121023.GF5801@sirena.org.uk> (raw)
In-Reply-To: <20200522115235.rt3ay7lveimrgooa@mobilestation>

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On Fri, May 22, 2020 at 02:52:35PM +0300, Serge Semin wrote:
> On Fri, May 22, 2020 at 02:13:40PM +0300, Andy Shevchenko wrote:

> > > Changelog v4:
> > > - Get back ndelay() method to wait for an SPI transfer completion.
> > >   spi_delay_exec() isn't suitable for the atomic context.

> > OTOH we may teach spi_delay_exec() to perform atomic sleeps.

> Please, see it's implementation. It does atomic delay when the delay value
> is less than 10us. But selectively gets to the usleep_range() if value is
> greater than that.

Yes, I hadn't realised this was in atomic context - _delay_exec() is
just not safe to use there, it'll swich to a sleeping delay if the time
is long enough.

> > > +	while (dw_spi_dma_tx_busy(dws) && retry--)
> > > +		ndelay(ns);

> > I might be mistaken, but I think I told that this one misses to keep power
> > management in mind.

> Here we already in nearly atomic context due to the callback executed in the
> tasklet. What power management could be during a tasklet execution? Again we
> can't call sleeping methods in here. What do you suggest in substitution?

You'd typically have a cpu_relax() in there as well as the ndelay().

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  parent reply	other threads:[~2020-05-22 12:10 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-22  0:07 [PATCH v4 00/16] spi: dw: Add generic DW DMA controller support Serge Semin
2020-05-22  0:07 ` [PATCH v4 02/16] spi: dw: Enable interrupts in accordance with DMA xfer mode Serge Semin
2020-05-22  0:07 ` [PATCH v4 04/16] spi: dw: Discard unused void priv pointer Serge Semin
2020-05-22  0:07 ` [PATCH v4 06/16] spi: dw: Parameterize the DMA Rx/Tx burst length Serge Semin
2020-05-22 11:06   ` Andy Shevchenko
2020-05-22  0:07 ` [PATCH v4 07/16] spi: dw: Use DMA max burst to set the request thresholds Serge Semin
2020-05-22  0:08 ` [PATCH v4 11/16] spi: dw: Remove DW DMA code dependency from DW_DMAC_PCI Serge Semin
2020-05-22  0:08 ` [PATCH v4 12/16] spi: dw: Add DW SPI DMA/PCI/MMIO dependency on the DW SPI core Serge Semin
2020-05-22 11:07   ` Andy Shevchenko
2020-05-22 11:08     ` Andy Shevchenko
2020-05-22  0:08 ` [PATCH v4 14/16] spi: dw: Add DMA support to the DW SPI MMIO driver Serge Semin
2020-05-22  0:08 ` [PATCH v4 16/16] dt-bindings: spi: Convert DW SPI binding to DT schema Serge Semin
2020-05-28 23:28   ` Rob Herring
     [not found] ` <20200522000806.7381-2-Sergey.Semin@baikalelectronics.ru>
2020-05-22 11:13   ` [PATCH v4 01/16] spi: dw: Add Tx/Rx finish wait methods to the MID DMA Andy Shevchenko
     [not found]     ` <20200522115235.rt3ay7lveimrgooa@mobilestation>
2020-05-22 12:10       ` Mark Brown [this message]
2020-05-22 12:12       ` Andy Shevchenko
2020-05-22 12:18         ` Mark Brown
2020-05-22 12:34           ` Andy Shevchenko
     [not found]             ` <20200522124406.co7gmteojfsooerc@mobilestation>
     [not found]               ` <20200522131013.GH5801@sirena.org.uk>
     [not found]                 ` <20200522132742.taf2ixfjpyd5u3dt@mobilestation>
     [not found]                   ` <20200522140025.bmd6bhpjjk5msvsm@mobilestation>
2020-05-22 14:36                     ` Andy Shevchenko
     [not found]                       ` <20200522144542.brhibh453wid2d6v@mobilestation>
2020-05-22 15:22                         ` Mark Brown
2020-05-23  8:34                           ` Serge Semin
2020-05-25 11:41                             ` Mark Brown
2020-05-25 21:36                               ` Serge Semin

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