Gitweb: http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=f6febccd7f86fbe94858a4a32d9384cc014c9f40 Commit: f6febccd7f86fbe94858a4a32d9384cc014c9f40 Parent: 4f9d5f4a353440f2265781bfa641587964901861 Author: Atsushi Nemoto <[EMAIL PROTECTED]> AuthorDate: Sat Feb 23 15:23:39 2008 -0800 Committer: Linus Torvalds <[EMAIL PROTECTED]> CommitDate: Sat Feb 23 17:12:14 2008 -0800
atmel_spi: fix clock polarity The atmel_spi driver does not initialize clock polarity correctly (except for at91rm9200 CS0 channel) in some case. The atmel_spi driver uses gpio-controlled chipselect. OTOH spi clock signal is controlled by CSRn.CPOL bit, but this register controls clock signal correctly only in 'real transfer' duration. At the time of cs_activate() call, CSRn.CPOL will be initialized correctly, but the controller do not know which channel is to be used next, so clock signal will stay at the inactive state of last transfer. If clock polarity of new transfer and last transfer was differ, new transfer will start with wrong clock signal state. For example, if you started SPI MODE 2 or 3 transfer after SPI MODE 0 or 1 transfer, the clock signal state at the assertion of chipselect will be low. Of course this will violates SPI transfer. This patch is short term solution for this problem. It makes all CSRn.CPOL match for the transfer before activating chipselect. For longer term, the best fix might be to let NPCS0 stay selected permanently in MR and overwrite CSR0 with to the new slave's settings before asserting CS. Signed-off-by: Atsushi Nemoto <[EMAIL PROTECTED]> Acked-by: Haavard Skinnemoen <[EMAIL PROTECTED]> Cc: David Brownell <[EMAIL PROTECTED]> Signed-off-by: Andrew Morton <[EMAIL PROTECTED]> Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]> --- drivers/spi/atmel_spi.c | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-) diff --git a/drivers/spi/atmel_spi.c b/drivers/spi/atmel_spi.c index 293b7ca..85687aa 100644 --- a/drivers/spi/atmel_spi.c +++ b/drivers/spi/atmel_spi.c @@ -87,6 +87,16 @@ static void cs_activate(struct atmel_spi *as, struct spi_device *spi) unsigned gpio = (unsigned) spi->controller_data; unsigned active = spi->mode & SPI_CS_HIGH; u32 mr; + int i; + u32 csr; + u32 cpol = (spi->mode & SPI_CPOL) ? SPI_BIT(CPOL) : 0; + + /* Make sure clock polarity is correct */ + for (i = 0; i < spi->master->num_chipselect; i++) { + csr = spi_readl(as, CSR0 + 4 * i); + if ((csr ^ cpol) & SPI_BIT(CPOL)) + spi_writel(as, CSR0 + 4 * i, csr ^ SPI_BIT(CPOL)); + } mr = spi_readl(as, MR); mr = SPI_BFINS(PCS, ~(1 << spi->chip_select), mr); - To unsubscribe from this list: send the line "unsubscribe git-commits-head" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html