From 2cf3683472f043e6748c48228df6d8a35a47ecc2 Mon Sep 17 00:00:00 2001 From: Yi Li Date: Mon, 6 Apr 2009 19:00:44 -0700 Subject: [PATCH 1/1] Blackfin SPI Driver: fix bug - spi controller driver does not assert/deassert CS correctly This bug can be observed when two SPI devices are sharing the spi bus: One device is set as SPI CS 7, another one is using SPI CS 4. In spi_bfin5xx.c: cs_active(), cs_deactive() are used to control SPI_FLG register. From the debug bellow: cs_active: flag: 0x7f91, chip->flag: 0x7f80, cs: 7 cs_active: flag: 0xef91, chip->flag: 0xef10, cs: 4 When device A (cs_7) activate CS 7, SPI_FLG is set as 0x7f91 (however, SPI_FLG should be set as 0x7f80, or 0x6f91 if in broadcast mode). Due to some HW bug (very possibly), if SPI_FLG is set as 0x7f91, SPISSEL7 is asserted, however SPISSEL4 will be asserted too (I can see this using the scope). This is unreasonable according to HRM. Signed-off-by: Yi Li Signed-off-by: Bryan Wu Acked-by: David Brownell Cc: David Brownell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/spi/spi_bfin5xx.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/spi/spi_bfin5xx.c b/drivers/spi/spi_bfin5xx.c index 317731a..1222925 100644 --- a/drivers/spi/spi_bfin5xx.c +++ b/drivers/spi/spi_bfin5xx.c @@ -189,6 +189,7 @@ static void cs_deactive(struct driver_data *drv_data, struct chip_data *chip) { u16 flag = read_FLAG(drv_data); + flag &= ~chip->flag; flag |= (chip->flag << 8); write_FLAG(drv_data, flag); @@ -1036,7 +1037,6 @@ static int setup(struct spi_device *spi) struct bfin5xx_spi_chip *chip_info = NULL; struct chip_data *chip; struct driver_data *drv_data = spi_master_get_devdata(spi->master); - u8 spi_flg; /* Abort device setup if requested features are not supported */ if (spi->mode & ~(SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST)) { @@ -1119,8 +1119,7 @@ static int setup(struct spi_device *spi) * SPI_BAUD, not the real baudrate */ chip->baud = hz_to_spi_baud(spi->max_speed_hz); - spi_flg = ~(1 << (spi->chip_select)); - chip->flag = ((u16) spi_flg << 8) | (1 << (spi->chip_select)); + chip->flag = 1 << (spi->chip_select); chip->chip_select_num = spi->chip_select; switch (chip->bits_per_word) { -- 1.8.2.3