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authorJulius Werner <jwerner@chromium.org>2014-09-24 15:40:49 -0700
committerPatrick Georgi <pgeorgi@google.com>2015-04-10 11:57:44 +0200
commit886d29bcd808476e0e83f68e3f7905fba4304b0a (patch)
treebb77525bc88e1cbc2bd35737bd5441e36e691507 /src/lib
parenteaa9c4596b083ee1d1a48c5e7632abdb5b7e5297 (diff)
downloadcoreboot-886d29bcd808476e0e83f68e3f7905fba4304b0a.tar.xz
gpio: Remove non-ternary tristate mode, make ternaries easier
The function to read board IDs from tristate GPIOs currently supports two output modes: a normal base-3 integer, or a custom format where every two bits represent one tristate pin. Each board decides which representation to use on its own, which is inconsistent and provides another possible gotcha to trip over when reading unfamiliar code. The two-bits-per-pin format creates the additional problem that a complete list of IDs (such as some boards use to build board-ID tables) necessarily has "holes" in them (since 0b11 does not correspond to a possible pin state), which makes them extremely tricky to write, read and expand. It's also very unintuitive in my opinion, although it was intended to make it easier to read individual pin states from a hex representation. This patch switches all boards over to base-3 and removes the other format to improve consistency. The tristate reading function will just print the pin states as they are read to make it easier to debug them, and we add a new BASE3() macro that can generate ternary numbers from pin states. Also change the order of all static initializers of board ID pin lists to write the most significant bit first, hoping that this can help clear up confusion about the endianness of the pins. CQ-DEPEND=CL:219902 BUG=None TEST=Booted on a Nyan_Blaze (with board ID 1, unfortunately the only one I have). Compiled on Daisy, Peach_Pit, Nyan, Nyan_Big, Nyan_Blaze, Rush, Rush_Ryu, Storm, Veryon_Pinky and Falco for good measure. Change-Id: I3ce5a0829f260db7d7df77e6788c2c6d13901b8f Signed-off-by: Patrick Georgi <pgeorgi@chromium.org> Original-Commit-Id: 2fa9545ac431c9af111ee4444d593ee4cf49554d Original-Change-Id: I6133cdaf01ed6590ae07e88d9e85a33dc013211a Original-Signed-off-by: Julius Werner <jwerner@chromium.org> Original-Reviewed-on: https://chromium-review.googlesource.com/219901 Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org> Reviewed-on: http://review.coreboot.org/9401 Tested-by: build bot (Jenkins) Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Diffstat (limited to 'src/lib')
-rw-r--r--src/lib/tristate_gpios.c15
1 files changed, 9 insertions, 6 deletions
diff --git a/src/lib/tristate_gpios.c b/src/lib/tristate_gpios.c
index 5ee5580ae8..0967a8f4be 100644
--- a/src/lib/tristate_gpios.c
+++ b/src/lib/tristate_gpios.c
@@ -17,10 +17,12 @@
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
+#include <base3.h>
+#include <console/console.h>
#include <delay.h>
#include <gpio.h>
-int gpio_get_tristates(gpio_t gpio[], int num_gpio, int tertiary)
+int gpio_get_tristates(gpio_t gpio[], int num_gpio)
{
/*
* GPIOs which are tied to stronger external pull up or pull down
@@ -31,6 +33,7 @@ int gpio_get_tristates(gpio_t gpio[], int num_gpio, int tertiary)
* internally pulled to.
*/
+ static const char tristate_char[] = {[0] = '0', [1] = '1', [Z] = 'Z'};
int temp;
int index;
int id = 0;
@@ -62,14 +65,14 @@ int gpio_get_tristates(gpio_t gpio[], int num_gpio, int tertiary)
* 1: pull up
* 2: floating
*/
+ printk(BIOS_DEBUG, "Reading tristate GPIOs: ");
for (index = num_gpio - 1; index >= 0; --index) {
- if (tertiary)
- id *= 3;
- else
- id <<= 2;
temp = gpio_get(gpio[index]);
- id += ((value[index] ^ temp) << 1) | temp;
+ temp |= ((value[index] ^ temp) << 1);
+ printk(BIOS_DEBUG, "%c ", tristate_char[temp]);
+ id = (id * 3) + temp;
}
+ printk(BIOS_DEBUG, "= %d\n", id);
/* Disable pull up / pull down to conserve power */
for (index = 0; index < num_gpio; ++index)