shinys000114/linux
1
0
Fork 0
mirror of https://github.com/hardkernel/linux.git synced 2026-06-07 11:26:02 +09:00
Code Issues Packages Projects Releases Wiki Activity

UPSTREAM: spi: add software implementation for SPI_CS_WORD

Browse Source 
This adds a default software implementation for the SPI_CS_WORD flag for
controllers that don't have such a feature.

The SPI_CS_WORD flag indicates that the CS line should be toggled
between each word sent, not just between each transfer. The
implementation works by using existing functions to split transfers into
one-word-sized transfers and sets the cs_change bit for each of the
new transfers.

Change-Id: Iaf210b28f14ae7319e689ef5c411d8a17fdd04ce
Signed-off-by: David Lechner <david@lechnology.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Jon Lin <jon.lin@rock-chips.com>
(cherry picked from commit cbaa62e009)
This commit is contained in:
David Lechner
2018-09-12 19:39:18 -05:00
committed by Tao Huang
parent d41a1fe15e
commit 4353a70bdb
1 changed files with 30 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
drivers/spi/spi.c
View File

@@ -2785,8 +2785,10 @@ int spi_setup(struct spi_device *spi)
return -EINVAL;
/* help drivers fail *cleanly* when they need options
* that aren't supported with their current controller
* SPI_CS_WORD has a fallback software implementation,
* so it is ignored here.
*/
bad_bits = spi->mode & ~spi->controller->mode_bits;
bad_bits = spi->mode & ~(spi->controller->mode_bits | SPI_CS_WORD);
ugly_bits = bad_bits &
(SPI_TX_DUAL | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD);
if (ugly_bits) {
@@ -2840,6 +2842,33 @@ static int __spi_validate(struct spi_device *spi, struct spi_message *message)
if (list_empty(&message->transfers))
return -EINVAL;
/* If an SPI controller does not support toggling the CS line on each
* transfer (indicated by the SPI_CS_WORD flag), we can emulate it by
* splitting transfers into one-word transfers and ensuring that
* cs_change is set for each transfer.
*/
if ((spi->mode & SPI_CS_WORD) && !(ctlr->mode_bits & SPI_CS_WORD)) {
size_t maxsize;
int ret;
maxsize = (spi->bits_per_word + 7) / 8;
/* spi_split_transfers_maxsize() requires message->spi */
message->spi = spi;
ret = spi_split_transfers_maxsize(ctlr, message, maxsize,
GFP_KERNEL);
if (ret)
return ret;
list_for_each_entry(xfer, &message->transfers, transfer_list) {
/* don't change cs_change on the last entry in the list */
if (list_is_last(&xfer->transfer_list, &message->transfers))
break;
xfer->cs_change = 1;
}
}
/* Half-duplex links include original MicroWire, and ones with
* only one data pin like SPI_3WIRE (switches direction) or where
* either MOSI or MISO is missing. They can also be caused by