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From: Lukas Wunner <lukas@wunner.de>
To: Mark Brown <broonie@kernel.org>,
	linux-spi@vger.kernel.org, dmaengine@vger.kernel.org,
	linux-rpi-kernel@lists.infradead.org,
	bcm-kernel-feedback-list@broadcom.com
Cc: Eric Anholt <eric@anholt.net>, Nuno Sa <nuno.sa@analog.com>,
	Martin Sperl <kernel@martin.sperl.org>,
	Noralf Tronnes <noralf@tronnes.org>,
	Robert Jarzmik <robert.jarzmik@free.fr>,
	Florian Kauer <florian.kauer@koalo.de>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Ray Jui <rjui@broadcom.com>,
	Scott Branden <sbranden@broadcom.com>,
	Vinod Koul <vkoul@kernel.org>, Stefan Wahren <wahrenst@gmx.net>
Subject: Re: [PATCH 00/10] Raspberry Pi SPI speedups
Date: Sat, 7 Sep 2019 11:06:37 +0200
Message-ID: <20190907090637.macdahajrzjepluc@wunner.de> (raw)
In-Reply-To: <cover.1564825752.git.lukas@wunner.de>

Dear Mark,

On Sat, Aug 03, 2019 at 12:10:00PM +0200, Lukas Wunner wrote:
> So far the BCM2835 SPI driver cannot cope with TX-only and RX-only
> transfers (rx_buf or tx_buf is NULL) when using DMA:  It relies on
> the SPI core to convert them to full-duplex transfers by allocating
> and DMA-mapping a dummy rx_buf or tx_buf.  This costs performance.
> 
> Resolve by pre-allocating reusable DMA descriptors which cyclically
> clear the RX FIFO (for TX-only transfers) or zero-fill the TX FIFO
> (for RX-only transfers).  Patch [07/10] provides some numbers for
> the achieved latency improvement and CPU time reduction with an
> SPI Ethernet controller.  SPI displays should see a similar speedup.
> I've also made an effort to reduce peripheral and memory bus accesses.

Just a gentle ping, this patch set was posted to the list 5 weeks ago,
has all necessary acks and has been tested successfully by 2 people
besides myself.

Do you have any thoughts on it?  Any objections?

In case the patches no longer apply cleanly I've prepared this branch
based on your for-next branch of Aug 23 from which you can merge if
you prefer that:

https://github.com/l1k/linux/commits/bcm2835_spi_simplex_v1

However I can also repost if necessary.

(PS: Apologies for misspelling your name as "Marc" in my e-mail of Aug 24.)

Thanks,

Lukas

> Lukas Wunner (10):
>   dmaengine: bcm2835: Allow reusable descriptors
>   dmaengine: bcm2835: Allow cyclic transactions without interrupt
>   spi: Guarantee cacheline alignment of driver-private data
>   spi: bcm2835: Drop dma_pending flag
>   spi: bcm2835: Work around DONE bit erratum
>   spi: bcm2835: Cache CS register value for ->prepare_message()
>   spi: bcm2835: Speed up TX-only DMA transfers by clearing RX FIFO
>   dmaengine: bcm2835: Document struct bcm2835_dmadev
>   dmaengine: bcm2835: Avoid accessing memory when copying zeroes
>   spi: bcm2835: Speed up RX-only DMA transfers by zero-filling TX FIFO
> 
>  drivers/dma/bcm2835-dma.c |  38 +++-
>  drivers/spi/spi-bcm2835.c | 408 ++++++++++++++++++++++++++++++++------
>  drivers/spi/spi.c         |  18 +-
>  3 files changed, 390 insertions(+), 74 deletions(-)
> 
> -- 
> 2.20.1

  parent reply index

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-03 10:10 Lukas Wunner
2019-08-03 10:10 ` [PATCH 01/10] dmaengine: bcm2835: Allow reusable descriptors Lukas Wunner
2019-08-08 12:30   ` Vinod Koul
2019-08-03 10:10 ` [PATCH 04/10] spi: bcm2835: Drop dma_pending flag Lukas Wunner
2019-08-03 10:10 ` [PATCH 05/10] spi: bcm2835: Work around DONE bit erratum Lukas Wunner
2019-08-11 19:45   ` Stefan Wahren
2019-08-11 19:57     ` Lukas Wunner
2019-08-11 20:29       ` Eric Anholt
2019-08-19 19:20       ` Stefan Wahren
2019-08-03 10:10 ` [PATCH 09/10] dmaengine: bcm2835: Avoid accessing memory when copying zeroes Lukas Wunner
2019-08-08 12:31   ` Vinod Koul
2019-08-03 10:10 ` [PATCH 07/10] spi: bcm2835: Speed up TX-only DMA transfers by clearing RX FIFO Lukas Wunner
2019-08-03 10:10 ` [PATCH 06/10] spi: bcm2835: Cache CS register value for ->prepare_message() Lukas Wunner
2019-08-03 10:10 ` [PATCH 02/10] dmaengine: bcm2835: Allow cyclic transactions without interrupt Lukas Wunner
2019-08-08 12:30   ` Vinod Koul
2019-08-03 10:10 ` [PATCH 08/10] dmaengine: bcm2835: Document struct bcm2835_dmadev Lukas Wunner
2019-08-08 12:31   ` Vinod Koul
2019-08-03 10:10 ` [PATCH 10/10] spi: bcm2835: Speed up RX-only DMA transfers by zero-filling TX FIFO Lukas Wunner
2019-08-03 10:10 ` [PATCH 03/10] spi: Guarantee cacheline alignment of driver-private data Lukas Wunner
2019-09-10 11:29   ` Mark Brown
2019-08-03 16:01 ` [PATCH 00/10] Raspberry Pi SPI speedups Noralf Trønnes
2019-08-11 19:50 ` Stefan Wahren
2019-08-11 19:52   ` Lukas Wunner
2019-08-19 19:22 ` Stefan Wahren
2019-08-21 15:21 ` kernel
2019-08-24 10:33 ` Lukas Wunner
2019-09-07  9:06 ` Lukas Wunner [this message]
2019-09-09 16:56   ` Mark Brown
2019-09-10 11:21   ` Mark Brown

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