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a44648b057
Long ago I've noticed (but didn't pay much attention) that spi_mpc83xx using PM calculations that differs from what specs describe. I.e. u8 pm = mpc83xx_spi->spibrg / (spi->max_speed_hz * 4); While specs says: "The SPI baud rate generator clock source (either system clock or system clock divided by 16, depending on DIV16 bit) is divided by 4 * ([PM] + 1), a range from 4 to 64.". Thus " - 1" is missing in the spi_mpc83xx's formula. Why nobody noticed that bug? Probably because sysclk usually less then user expects, e.g. you expect 200 MHz, but real clock is 198 MHz, and integer rounding helps when this formula is used. Suppose it's SPI in QE, SYSCLK at 198 MHz, thus SPIBRG at 99MHz, 25 MHz requested. PM = (99MHz / ( 25 MHz * 4 )), PM == 0, output SPICLK will be 24.75 MHz At lower frequencies this bug is more noticeable, though. And this bug shows itself in all its beauty if SYSCLK is equal or a bit more than you expect (200 MHz SYSCLK, 100 MHz SPIBRG): PM = (100MHz / ( 25 MHz * 4 )), PM == 1, output SPICLK will be 12.625 MHz! Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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| .. | ||
| at25.c | ||
| atmel_spi.c | ||
| atmel_spi.h | ||
| au1550_spi.c | ||
| Kconfig | ||
| Makefile | ||
| mpc52xx_psc_spi.c | ||
| omap2_mcspi.c | ||
| omap_uwire.c | ||
| pxa2xx_spi.c | ||
| spi.c | ||
| spi_bfin5xx.c | ||
| spi_bitbang.c | ||
| spi_butterfly.c | ||
| spi_imx.c | ||
| spi_lm70llp.c | ||
| spi_mpc83xx.c | ||
| spi_s3c24xx.c | ||
| spi_s3c24xx_gpio.c | ||
| spi_txx9.c | ||
| spidev.c | ||
| tle62x0.c | ||
| xilinx_spi.c | ||