Daniel Thompson has uploaded this change for review. ( https://review.coreboot.org/26947 Change subject: bitbang_spi: Half-duplex optimization ...................................................................... bitbang_spi: Half-duplex optimization Currently, the core of bitbang_spi is a full-duplex SPI loop but in practice this code is only ever used half-duplex. Spliting this code into two half duplex loops allows us to optimize performance by reducing communications and/or CPU pipeline stalls. Change-Id: I33b9f363716f651146c09113bda5fffe53b16738 Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> --- M bitbang_spi.c 1 file changed, 20 insertions(+), 5 deletions(-) git pull ssh://review.coreboot.org:29418/flashrom refs/changes/47/26947/1 diff --git a/bitbang_spi.c b/bitbang_spi.c index 2c7a3f1..3b5617b 100644 --- a/bitbang_spi.c +++ b/bitbang_spi.c @@ -119,14 +119,16 @@ return 0; } -static uint8_t bitbang_spi_rw_byte(const struct bitbang_spi_master *master, - uint8_t val) +static uint8_t bitbang_spi_read_byte(const struct bitbang_spi_master *master) { uint8_t ret = 0; int i; for (i = 7; i >= 0; i--) { - bitbang_spi_set_sck_set_mosi(master, 0, (val >> i) & 1); + if (i == 0) + bitbang_spi_set_sck_set_mosi(master, 0, 0); + else + bitbang_spi_set_sck(master, 0); programmer_delay(master->half_period); ret <<= 1; ret |= bitbang_spi_set_sck_get_miso(master, 1); @@ -135,6 +137,19 @@ return ret; } +static void bitbang_spi_write_byte(const struct bitbang_spi_master *master, + uint8_t val) +{ + int i; + + for (i = 7; i >= 0; i--) { + bitbang_spi_set_sck_set_mosi(master, 0, (val >> i) & 1); + programmer_delay(master->half_period); + bitbang_spi_set_sck(master, 1); + programmer_delay(master->half_period); + } +} + static int bitbang_spi_send_command(struct flashctx *flash, unsigned int writecnt, unsigned int readcnt, const unsigned char *writearr, @@ -150,9 +165,9 @@ bitbang_spi_request_bus(master); bitbang_spi_set_cs(master, 0); for (i = 0; i < writecnt; i++) - bitbang_spi_rw_byte(master, writearr[i]); + bitbang_spi_write_byte(master, writearr[i]); for (i = 0; i < readcnt; i++) - readarr[i] = bitbang_spi_rw_byte(master, 0); + readarr[i] = bitbang_spi_read_byte(master); bitbang_spi_set_sck(master, 0); programmer_delay(master->half_period); -- To view, visit https://review.coreboot.org/26947 To unsubscribe, or for help writing mail filters, visit https://review.coreboot.org/settings Gerrit-Project: flashrom Gerrit-Branch: master Gerrit-MessageType: newchange Gerrit-Change-Id: I33b9f363716f651146c09113bda5fffe53b16738 Gerrit-Change-Number: 26947 Gerrit-PatchSet: 1 Gerrit-Owner: Daniel Thompson <daniel.thompson@linaro.org>