From: Lukas Wunner <lukas@wunner.de>
To: Stefan Wahren <wahrenst@gmx.net>
Cc: Mark Brown <broonie@kernel.org>, Vinod Koul <vkoul@kernel.org>,
linux-spi@vger.kernel.org, dmaengine@vger.kernel.org,
linux-rpi-kernel@lists.infradead.org,
bcm-kernel-feedback-list@broadcom.com,
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>
Subject: Re: [PATCH 00/10] Raspberry Pi SPI speedups
Date: Sun, 11 Aug 2019 21:52:35 +0200 [thread overview]
Message-ID: <20190811195235.gojfdgubq7zheino@wunner.de> (raw)
In-Reply-To: <fc10f730-6916-7f24-3185-5bdb39a965c9@gmx.net>
On Sun, Aug 11, 2019 at 09:50:17PM +0200, Stefan Wahren wrote:
> Am 03.08.19 um 12:10 schrieb Lukas Wunner:
> > 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.
>
> i know the BCM2711 / Raspberry Pi 4 isn't upstreamed yet, but this
> series hasn't been tested with RPi 4?
No, I only have the CM1 and CM3 at my disposal for testing,
the series seemed to work fine on both.
Thanks,
Lukas
next prev parent reply other threads:[~2019-08-11 19:52 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-03 10:10 [PATCH 00/10] Raspberry Pi SPI speedups 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 [this message]
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
2019-09-09 16:56 ` Mark Brown
2019-09-10 11:21 ` Mark Brown
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