Messages in this thread | | | From | David Brownell <> | Subject | Re: [PATCH 16/16] Blackfin SPI Driver: fix bug - correct usage of struct spi_transfer.cs_change | Date | Thu, 20 Nov 2008 12:51:33 -0800 |
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On Monday 17 November 2008, Bryan Wu wrote: > From: Yi Li <yi.li@analog.com> > > According to comments in linux/spi/spi.h: > > * All SPI transfers start with the relevant chipselect active. Normally > * it stays selected until after the last transfer in a message. Drivers > * can affect the chipselect signal using cs_change. > * > * (i) If the transfer isn't the last one in the message, this flag is > * used to make the chipselect briefly go inactive in the middle of the > * message. Toggling chipselect in this way may be needed to terminate > * a chip command, letting a single spi_message perform all of group of > * chip transactions together. > * > * (ii) When the transfer is the last one in the message, the chip may > * stay selected until the next transfer. On multi-device SPI busses > * with nothing blocking messages going to other devices, this is just > * a performance hint; starting a message to another device deselects > * this one. But in other cases, this can be used to ensure correctness. > * Some devices need protocol transactions to be built from a series of > * spi_message submissions, where the content of one message is determined > * by the results of previous messages and where the whole transaction > * ends when the chipselect goes intactive. > > Signed-off-by: Yi Li <yi.li@analog.com> > Signed-off-by: Bryan Wu <cooloney@kernel.org>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
> --- > drivers/spi/spi_bfin5xx.c | 15 ++++++++------- > 1 files changed, 8 insertions(+), 7 deletions(-) > > diff --git a/drivers/spi/spi_bfin5xx.c b/drivers/spi/spi_bfin5xx.c > index 8cf5d6e..0e3102a 100644 > --- a/drivers/spi/spi_bfin5xx.c > +++ b/drivers/spi/spi_bfin5xx.c > @@ -540,15 +540,13 @@ static void giveback(struct driver_data *drv_data) > > msg->state = NULL; > > - /* disable chip select signal. And not stop spi in autobuffer mode */ > - if (drv_data->tx_dma != 0xFFFF) { > - cs_deactive(drv_data, chip); > - bfin_spi_disable(drv_data); > - } > - > if (!drv_data->cs_change) > cs_deactive(drv_data, chip); > > + /* Not stop spi in autobuffer mode */ > + if (drv_data->tx_dma != 0xFFFF) > + bfin_spi_disable(drv_data); > + > if (msg->complete) > msg->complete(msg->context); > } > @@ -757,7 +755,8 @@ static void pump_transfers(unsigned long data) > > write_STAT(drv_data, BIT_STAT_CLR); > cr = (read_CTRL(drv_data) & (~BIT_CTL_TIMOD)); > - cs_active(drv_data, chip); > + if (drv_data->cs_change) > + cs_active(drv_data, chip); > > dev_dbg(&drv_data->pdev->dev, > "now pumping a transfer: width is %d, len is %d\n", > @@ -920,6 +919,8 @@ static void pump_transfers(unsigned long data) > message->state = next_transfer(drv_data); > } > > + if (drv_data->cs_change) > + cs_active(drv_data, chip); > /* Schedule next transfer tasklet */ > tasklet_schedule(&drv_data->pump_transfers); > > -- > 1.5.6.3 > >
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