linux/drivers/spi
Lukas Wunner 3bd7f6589f
spi: bcm2835: Overcome sglist entry length limitation
When in DMA mode, the BCM2835 SPI controller requires that the FIFO is
accessed in 4 byte chunks.  This rule is not fulfilled if a transfer
consists of multiple sglist entries, one per page, and the first entry
starts in the middle of a page with an offset not a multiple of 4.

The driver currently falls back to programmed I/O for such transfers,
incurring a significant performance penalty.

Overcome this hardware limitation by transferring the first few bytes of
a transfer without DMA such that the remainder of the first sglist entry
becomes a multiple of 4.  Specifics are provided in kerneldoc comments.

An alternative approach would have been to split transfers in the
->prepare_message hook, but this may necessitate two transfers per page,
defeating the goal of clustering multiple pages together in a single
transfer for efficiency.  E.g. if the first TX sglist entry's length is
23 and the first RX's is 40, the first transfer would send and receive
23 bytes, the second 40 - 23 = 17 bytes, the third 4096 - 17 = 4079
bytes, the fourth 4096 - 4079 = 17 bytes and so on.  In other words,
O(n) transfers are necessary (n = number of sglist entries), whereas
the algorithm implemented herein only requires O(1) additional work.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Mathias Duckeck <m.duckeck@kunbus.de>
Cc: Frank Pavlic <f.pavlic@kunbus.de>
Cc: Martin Sperl <kernel@martin.sperl.org>
Cc: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
2018-11-28 15:58:15 +00:00
..
internals.h spi: Add an helper to flush the message queue 2018-04-23 15:48:18 +01:00
Kconfig spi: npcm: add NPCM PSPI controller driver 2018-11-13 12:01:22 -08:00
Makefile spi: npcm: add NPCM PSPI controller driver 2018-11-13 12:01:22 -08:00
spi-altera.c spi: altera: Consolidate TX/RX data register access 2017-08-16 11:53:31 +01:00
spi-armada-3700.c Merge remote-tracking branches 'spi/topic/a3700', 'spi/topic/atmel', 'spi/topic/bcm53xx', 'spi/topic/davinci' and 'spi/topic/dw' into spi-next 2018-01-26 17:57:24 +00:00
spi-at91-usart.c spi: at91-usart: add power management support 2018-11-27 14:15:11 +00:00
spi-ath79.c spi: add flags parameter to txrx_word function pointers 2018-08-01 14:50:24 +01:00
spi-atmel.c spi: Do not print a message if spi_controller_{suspend,resume}() fails 2018-09-05 12:38:27 +01:00
spi-au1550.c
spi-axi-spi-engine.c spi: spi-axi: fix potential use-after-free after deregistration 2017-10-31 11:15:10 +00:00
spi-bcm63xx-hsspi.c spi/bcm63xx-hsspi: keep pll clk enabled 2018-09-18 09:16:34 -07:00
spi-bcm63xx.c spi/bcm63xx: fix error return code in bcm63xx_spi_probe() 2017-08-08 11:36:35 +01:00
spi-bcm2835.c spi: bcm2835: Overcome sglist entry length limitation 2018-11-28 15:58:15 +00:00
spi-bcm2835aux.c spi: bcm2835: make license text and module license match 2018-11-14 14:18:18 -08:00
spi-bcm-qspi.c spi: bcm-qspi: switch back to reading flash using smaller chunks 2018-10-11 15:00:34 +01:00
spi-bcm-qspi.h
spi-bitbang-txrx.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
spi-bitbang.c spi: spi-gpio: add SPI_3WIRE support 2018-08-01 14:50:28 +01:00
spi-brcmstb-qspi.c
spi-butterfly.c spi: add flags parameter to txrx_word function pointers 2018-08-01 14:50:24 +01:00
spi-cadence.c spi: cadence: Fix missing clk_disable_unprepare() on error in cnds_runtime_resume() 2018-07-11 15:34:53 +01:00
spi-cavium-octeon.c
spi-cavium-thunderx.c
spi-cavium.c
spi-cavium.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
spi-clps711x.c
spi-coldfire-qspi.c
spi-davinci.c spi: spi-davinci: Don't error when SPI_CS_WORD and cs_gpio 2018-09-18 10:40:34 -07:00
spi-dln2.c
spi-dw-mid.c spi: dw: Convert to generalized SPI controller API 2018-02-12 12:04:16 +00:00
spi-dw-mmio.c dw: spi: add support for Amazon's Alpine spi controller 2018-10-11 15:11:04 +01:00
spi-dw-pci.c
spi-dw.c dw: spi: add support for Amazon's Alpine spi controller 2018-10-11 15:11:04 +01:00
spi-dw.h dw: spi: add support for Amazon's Alpine spi controller 2018-10-11 15:11:04 +01:00
spi-efm32.c
spi-ep93xx.c spi: spi-ep93xx: Use dma_data_direction for ep93xx_spi_dma_{finish,prepare} 2018-10-09 00:11:28 +01:00
spi-falcon.c spi: spi-falcon: drop check of boot select 2017-09-01 11:33:22 +01:00
spi-fsl-cpm.c
spi-fsl-cpm.h
spi-fsl-dspi.c spi: spi-fsl-dspi: use IRQF_SHARED mode to request IRQ 2018-11-05 11:53:28 +00:00
spi-fsl-espi.c spi: Do not print a message if spi_controller_{suspend,resume}() fails 2018-09-05 12:38:27 +01:00
spi-fsl-lib.c
spi-fsl-lib.h
spi-fsl-lpspi.c spi: fsl-lpspi: Prevent FIFO under/overrun by default 2018-10-10 12:41:36 +01:00
spi-fsl-spi.c Merge remote-tracking branches 'spi/topic/devprop', 'spi/topic/fsl', 'spi/topic/fsl-dspi', 'spi/topic/imx' and 'spi/topic/lantiq' into spi-next 2017-04-26 15:58:04 +01:00
spi-fsl-spi.h
spi-geni-qcom.c spi: spi-geni-qcom: Simplify probe function 2018-11-05 11:53:52 +00:00
spi-gpio.c Merge branch 'spi-4.20' into spi-next 2018-10-21 17:00:14 +01:00
spi-img-spfi.c spi: img-spfi: Set device select bits for SPFI port state 2018-07-30 16:31:54 +01:00
spi-imx.c spi: imx: use PIO mode if size is small 2018-10-12 18:54:02 +02:00
spi-iproc-qspi.c
spi-jcore.c spi: jcore: disable ref_clk after getting its rate 2018-03-18 17:57:42 -07:00
spi-lantiq-ssc.c Merge remote-tracking branches 'spi/topic/devprop', 'spi/topic/fsl', 'spi/topic/fsl-dspi', 'spi/topic/imx' and 'spi/topic/lantiq' into spi-next 2017-04-26 15:58:04 +01:00
spi-lm70llp.c spi: add flags parameter to txrx_word function pointers 2018-08-01 14:50:24 +01:00
spi-loopback-test.c spi: loopback-test: implement testing with no CS 2017-07-26 13:08:56 +01:00
spi-lp8841-rtc.c
spi-mem.c spi: spi-mem: Fix inverted logic in op sanity check 2018-09-27 23:29:57 +01:00
spi-meson-spicc.c spi: meson-spicc: Fix error handling in meson_spicc_probe() 2018-05-02 05:59:21 +09:00
spi-meson-spifc.c
spi-mpc52xx-psc.c
spi-mpc52xx.c spi: mpc52xx: Use gpio_is_valid() 2018-04-27 12:05:39 +01:00
spi-mpc512x-psc.c
spi-mt65xx.c spi: mediatek: add spi support for mt7629 IC 2018-11-27 14:17:20 +00:00
spi-mxic.c spi: Add MXIC controller driver 2018-11-05 11:55:06 +00:00
spi-mxs.c spi: mxs: Switch to SPDX identifier 2018-05-03 10:27:43 +09:00
spi-npcm-pspi.c spi: npcm: Fix uninitialized variable warning 2018-11-27 14:07:08 +00:00
spi-nuc900.c
spi-oc-tiny.c treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
spi-omap2-mcspi.c spi: omap2-mcspi: Add missing suspend and resume calls 2018-11-15 16:20:43 -08:00
spi-omap-100k.c
spi-omap-uwire.c
spi-orion.c spi: orion: cosmetics - alias long direct_access variables 2018-09-03 15:14:18 +01:00
spi-pic32-sqi.c spi: pic32-sqi: don't pass GFP_DMA32 to dma_alloc_coherent 2018-10-17 11:11:32 +01:00
spi-pic32.c spi: pic32: Use proper enum in dmaengine_prep_slave_rg 2018-09-20 18:11:22 -07:00
spi-pl022.c spi: pl022: Handle cs_change for last transfer 2018-11-13 10:05:49 -08:00
spi-ppc4xx.c
spi-pxa2xx-dma.c spi: pxa2xx: Use core message processing loop 2018-04-17 17:11:30 +01:00
spi-pxa2xx-pci.c spi: pca2xx-pci: Allow MSI 2017-01-23 18:09:37 +00:00
spi-pxa2xx.c spi: pxa2xx: Fix '"CONFIG_OF" is not defined' warning 2018-11-16 19:06:24 -08:00
spi-pxa2xx.h spi: pxa2xx: Add ready signal 2018-11-13 10:02:09 -08:00
spi-qcom-qspi.c spi: Introduce new driver for Qualcomm QuadSPI controller 2018-10-11 15:11:09 +01:00
spi-qup.c spi: qup: fix 64-bit build warning 2017-08-10 15:50:23 +01:00
spi-rb4xx.c spi: rb4xx: Use SPI_BPW_MASK to set bits_per_word_mask 2018-10-10 12:48:06 +01:00
spi-rockchip.c spi: rockchip: support lsb-first mode 2018-11-05 11:42:43 +00:00
spi-rspi.c spi: spi-rspi: simplify getting .driver_data 2018-11-05 11:54:50 +00:00
spi-s3c24xx-fiq.h
spi-s3c24xx-fiq.S
spi-s3c24xx.c
spi-s3c64xx.c spi: spi-s3c64xx: Fix system resume support 2018-05-17 13:27:08 +09:00
spi-sc18is602.c spi: sc18is602: Add OF device ID table 2017-02-22 10:50:09 -08:00
spi-sh-hspi.c spi: use SPDX identifier for Renesas drivers 2018-08-28 20:32:00 +01:00
spi-sh-msiof.c spi: spi-sh-msiof: simplify getting .driver_data 2018-11-05 11:54:20 +00:00
spi-sh-sci.c spi: add flags parameter to txrx_word function pointers 2018-08-01 14:50:24 +01:00
spi-sh.c spi: use SPDX identifier for Renesas drivers 2018-08-28 20:32:00 +01:00
spi-sirf.c spi: sirf: account for const type of of_device_id.data 2018-01-03 11:38:46 +00:00
spi-slave-mt27xx.c spi: mediatek: add spi slave for Mediatek MT2712 2018-09-28 14:29:14 +01:00
spi-slave-system-control.c spi: slave: Fix missing break in switch 2018-10-03 16:23:10 +01:00
spi-slave-time.c spi: slave: Add SPI slave handler reporting uptime at previous message 2017-05-26 13:12:04 +01:00
spi-sprd-adi.c spi: sprd: Change to use devm_hwspin_lock_request_specific() 2018-06-26 13:52:27 -07:00
spi-sprd.c spi: sprd: don't mark remove function as __exit 2018-09-27 23:26:43 +01:00
spi-st-ssc4.c spi: st-ssc4: whitespace cleanup 2017-05-26 12:41:07 +01:00
spi-stm32-qspi.c spi: spi-mem: add stm32 qspi controller 2018-10-19 13:32:56 +01:00
spi-stm32.c spi: stm32: Fix error handling in stm32_spi_probe() 2018-04-17 11:46:23 +01:00
spi-sun4i.c spi: sun4i: disable clocks in the remove function 2017-12-07 11:59:15 +00:00
spi-sun6i.c spi: sun6i: disable/unprepare clocks on remove 2017-12-07 17:45:17 +00:00
spi-tegra20-sflash.c spi: tegra20-sflash: explicitly request exclusive reset control 2017-07-19 17:06:31 +01:00
spi-tegra20-slink.c spi: tegra20-slink: explicitly enable/disable clock 2018-09-03 12:23:41 +01:00
spi-tegra114.c spi: tegra114: correct register name in definition 2017-10-09 10:16:38 +01:00
spi-test.h spi: loopback-test: add elapsed time check 2017-03-17 21:54:08 +00:00
spi-ti-qspi.c spi: ti-qspi: Make sure res_mmap != NULL before dereferencing it 2018-05-17 13:36:00 +09:00
spi-tle62x0.c
spi-topcliff-pch.c spi/topcliff-pch: Delete an error message for a failed memory allocation in pch_spi_set_tx() 2017-01-17 18:38:02 +00:00
spi-txx9.c
spi-uniphier.c spi: uniphier: remove unnecessary include headers 2018-08-02 11:08:06 +01:00
spi-xcomm.c
spi-xilinx.c spi: xilinx: Add support for xlnx,axi-quad-spi-1.00.a 2017-11-27 16:31:20 +00:00
spi-xlp.c spi: xlp: fix error return code in xlp_spi_probe() 2017-08-08 11:36:07 +01:00
spi-xtensa-xtfpga.c spi: add flags parameter to txrx_word function pointers 2018-08-01 14:50:24 +01:00
spi-zynqmp-gqspi.c spi: spi-zynqmp-gqspi: simplify getting .driver_data 2018-11-05 11:54:35 +00:00
spi.c spi: Fix core transfer waits after slave support 2018-11-15 16:08:32 -08:00
spidev.c spi: spidev: Fix OF tree warning logic 2018-10-10 13:46:54 +01:00