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    Subject[PATCH 15/16] Blackfin SPI Driver: fix bug - spi controller driver does not assert/deassert CS correctly
    Date
    From: Yi Li <yi.li@analog.com>

    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 <yi.li@analog.com>
    Signed-off-by: Bryan Wu <cooloney@kernel.org>
    ---
    drivers/spi/spi_bfin5xx.c | 5 ++---
    1 files changed, 2 insertions(+), 3 deletions(-)

    diff --git a/drivers/spi/spi_bfin5xx.c b/drivers/spi/spi_bfin5xx.c
    index 9c602ad..8cf5d6e 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);
    @@ -1032,7 +1033,6 @@ 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)) {
    @@ -1115,8 +1115,7 @@ 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) {
    --
    1.5.6.3

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