Daniel Thompson has uploaded this change for review.

View Change

bitbang_spi: Add functions to optimize xfers

On systems where the overhead of getting/setting pins is much greater
than the half period (for example, USB bit banging) it significantly
boosts performance if we can bang more than one bit at the same time.
Add support for setting sck at the same time as mosi or miso activity.

Change-Id: Ic3430a9df34844cdfa82e109456be788eaa1789a
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
---
M bitbang_spi.c
M programmer.h
2 files changed, 27 insertions(+), 16 deletions(-)

git pull ssh://review.coreboot.org:29418/flashrom refs/changes/46/26946/1

diff --git a/bitbang_spi.c b/bitbang_spi.c
index edbc3e9..2c7a3f1 100644
--- a/bitbang_spi.c
+++ b/bitbang_spi.c
@@ -32,16 +32,6 @@
 	master->set_sck(val);
 }
 
-static void bitbang_spi_set_mosi(const struct bitbang_spi_master * const master, int val)
-{
-	master->set_mosi(val);
-}
-
-static int bitbang_spi_get_miso(const struct bitbang_spi_master * const master)
-{
-	return master->get_miso();
-}
-
 static void bitbang_spi_request_bus(const struct bitbang_spi_master * const master)
 {
 	if (master->request_bus)
@@ -54,6 +44,26 @@
 		master->release_bus();
 }
 
+static void bitbang_spi_set_sck_set_mosi(const struct bitbang_spi_master * const master, int sck, int mosi)
+{
+	if (master->set_sck_set_mosi) {
+		master->set_sck_set_mosi(sck, mosi);
+		return;
+	}
+
+	master->set_sck(sck);
+	master->set_mosi(mosi);
+}
+
+static int bitbang_spi_set_sck_get_miso(const struct bitbang_spi_master * const master, int sck)
+{
+	if (master->set_sck_get_miso)
+		return master->set_sck_get_miso(sck);
+
+	master->set_sck(sck);
+	return master->get_miso();
+}
+
 static int bitbang_spi_send_command(struct flashctx *flash,
 				    unsigned int writecnt, unsigned int readcnt,
 				    const unsigned char *writearr,
@@ -101,8 +111,7 @@
 	/* Only mess with the bus if we're sure nobody else uses it. */
 	bitbang_spi_request_bus(master);
 	bitbang_spi_set_cs(master, 1);
-	bitbang_spi_set_sck(master, 0);
-	bitbang_spi_set_mosi(master, 0);
+	bitbang_spi_set_sck_set_mosi(master, 0, 0);
 	/* FIXME: Release SPI bus here and request it again for each command or
 	 * don't release it now and only release it on programmer shutdown?
 	 */
@@ -117,13 +126,11 @@
 	int i;
 
 	for (i = 7; i >= 0; i--) {
-		bitbang_spi_set_mosi(master, (val >> i) & 1);
+		bitbang_spi_set_sck_set_mosi(master, 0, (val >> i) & 1);
 		programmer_delay(master->half_period);
-		bitbang_spi_set_sck(master, 1);
 		ret <<= 1;
-		ret |= bitbang_spi_get_miso(master);
+		ret |= bitbang_spi_set_sck_get_miso(master, 1);
 		programmer_delay(master->half_period);
-		bitbang_spi_set_sck(master, 0);
 	}
 	return ret;
 }
@@ -147,6 +154,7 @@
 	for (i = 0; i < readcnt; i++)
 		readarr[i] = bitbang_spi_rw_byte(master, 0);
 
+	bitbang_spi_set_sck(master, 0);
 	programmer_delay(master->half_period);
 	bitbang_spi_set_cs(master, 1);
 	programmer_delay(master->half_period);
diff --git a/programmer.h b/programmer.h
index e49f262..7bb51eb 100644
--- a/programmer.h
+++ b/programmer.h
@@ -181,6 +181,9 @@
 	int (*get_miso) (void);
 	void (*request_bus) (void);
 	void (*release_bus) (void);
+	/* optional functions to optimize xfers */
+	void (*set_sck_set_mosi) (int sck, int mosi);
+	int (*set_sck_get_miso) (int sck);
 	/* Length of half a clock period in usecs. */
 	unsigned int half_period;
 };

To view, visit change 26946. To unsubscribe, or for help writing mail filters, visit settings.