The patch titled
atmel_spi throughput improvement
has been removed from the -mm tree. Its filename was
atmel_spi-throughput-improvement.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: atmel_spi throughput improvement
From: Haavard Skinnemoen <[EMAIL PROTECTED]>
Don't insert (undesirable) delays between consecutive words (DLYBCT) or when
activating chipselects (DLYBS).
Removing the between-word delays improves the performance of bulk transfers
(such as mtd_dataflash, m25p80, mmc_spi) significantly. In one test, the
improvement was a factor of more than eight!
(The large DLYBCT value came from the legacy at91 SPI driver, and it's not
clear why it used such a huge value.)
Signed-off-by: Haavard Skinnemoen <[EMAIL PROTECTED]>
Signed-off-by: David Brownell <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---
drivers/spi/atmel_spi.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff -puN drivers/spi/atmel_spi.c~atmel_spi-throughput-improvement
drivers/spi/atmel_spi.c
--- a/drivers/spi/atmel_spi.c~atmel_spi-throughput-improvement
+++ a/drivers/spi/atmel_spi.c
@@ -490,9 +490,14 @@ static int atmel_spi_setup(struct spi_de
if (!(spi->mode & SPI_CPHA))
csr |= SPI_BIT(NCPHA);
- /* TODO: DLYBS and DLYBCT */
- csr |= SPI_BF(DLYBS, 10);
- csr |= SPI_BF(DLYBCT, 10);
+ /* DLYBS is mostly irrelevant since we manage chipselect using GPIOs.
+ *
+ * DLYBCT would add delays between words, slowing down transfers.
+ * It could potentially be useful to cope with DMA bottlenecks, but
+ * in those cases it's probably best to just use a lower bitrate.
+ */
+ csr |= SPI_BF(DLYBS, 0);
+ csr |= SPI_BF(DLYBCT, 0);
/* chipselect must have been muxed as GPIO (e.g. in board setup) */
npcs_pin = (unsigned int)spi->controller_data;
_
Patches currently in -mm which might be from [EMAIL PROTECTED] are
origin.patch
git-avr32.patch
git-mtd.patch
sanitize-the-type-of-struct-useru_ar0.patch
add-cmpxchg_local-to-avr32.patch
tty-let-architectures-override-the-user-kernel-macros.patch
maintainers-add-haavard-as-maintainer-of-the-atmel_serial-driver.patch
atmel_serial-clean-up-the-code.patch
atmel_serial-use-cpu_relax-when-busy-waiting.patch
atmel_serial-use-existing-console-options-only-if-brg-is-running.patch
atmel_serial-fix-bugs-in-probe-error-path-and-remove.patch
atmel_serial-split-the-interrupt-handler.patch
atmel_serial-add-dma-support.patch
atmel_serial-add-dma-support-fix.patch
atmel_serial-fix-broken-rx-buffer-allocation.patch
atmel_serial-use-container_of-instead-of-direct-cast.patch
atmel_serial-show-tty-name-in-proc-interrupts.patch
basic-pwm-driver-for-avr32-and-at91.patch
basic-pwm-driver-for-avr32-and-at91-fix.patch
pwm-led-driver.patch
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