Hi Robert, I recently got the Weather Cape (rev b) and noticed an issue with the tsl2550 light sensor in low light. It turns out Matt Ranostay posted a patch to LKML back in 2013 that fixes the issue:
[PATCH] tsl2550: fix lux1_input error in low light https://lkml.org/lkml/2013/6/14/16 However, it doesn't seem that patch was ever picked up. I've applied the patch to 4.4.35-ti-r70 and tested OK. The patch also applies OK to mainline (4.9-rc7). More details in this gist (also attached): https://gist.github.com/pdp7/4c91813a9ca79aba200d20884a0a0d63 Could you add the attached patch to ti-linux-kernel-dev? thanks, drew -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CAPgEAj4tD6ppXk0V-LMC3fynqSvVjp4XDRYTES28wZzgk8VfMw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
From c23e541ef11dc848ca60218aa74690dbb0158114 Mon Sep 17 00:00:00 2001 From: "mranos...@gmail.com" <mranos...@gmail.com> Date: Mon, 3 Jun 2013 22:38:49 +0000 Subject: [PATCH] tsl2550: fix lux1_input error in low light ADC channel 0 photodiode detects both infrared + visible light, but ADC channel 1 just detects infrared. However, the latter is a bit more sensitive in that range so complete darkness or low light causes a error condition in which the chan0 - chan1 is negative that results in a -EAGAIN. This patch changes the resulting lux1_input sysfs attribute message from "Resource temporarily unavailable" to a user-grokable lux value of 0. Signed-off-by: Matt Ranostay <mranos...@gmail.com> --- drivers/misc/tsl2550.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/misc/tsl2550.c b/drivers/misc/tsl2550.c index 87a1337..eb57610 100644 --- a/drivers/misc/tsl2550.c +++ b/drivers/misc/tsl2550.c @@ -177,7 +177,7 @@ static int tsl2550_calculate_lux(u8 ch0, u8 ch1) } else lux = 0; else - return -EAGAIN; + return 0; /* LUX range check */ return lux > TSL2550_MAX_LUX ? TSL2550_MAX_LUX : lux; -- 2.9.3
## [PATCH] tsl2550: fix lux1_input error in low light [Patch from LKML post by Matt Ranostay](https://lkml.org/lkml/2013/6/14/16) ``` From c23e541ef11dc848ca60218aa74690dbb0158114 Mon Sep 17 00:00:00 2001 From: Matt Ranostay <mranos...@gmail.com> Date: Mon, 3 Jun 2013 22:38:49 +0000 Subject: [PATCH] tsl2550: fix lux1_input error in low light ADC channel 0 photodiode detects both infrared + visible light, but ADC channel 1 just detects infrared. However, the latter is a bit more sensitive in that range so complete darkness or low light causes a error condition in which the chan0 - chan1 is negative that results in a -EAGAIN. This patch changes the resulting lux1_input sysfs attribute message from "Resource temporarily unavailable" to a user-grokable lux value of 0. Signed-off-by: Matt Ranostay <mranos...@gmail.com> --- drivers/misc/tsl2550.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/misc/tsl2550.c b/drivers/misc/tsl2550.c index 87a1337..eb57610 100644 --- a/drivers/misc/tsl2550.c +++ b/drivers/misc/tsl2550.c @@ -177,7 +177,7 @@ static int tsl2550_calculate_lux(u8 ch0, u8 ch1) } else lux = 0; else - return -EAGAIN; + return 0; /* LUX range check */ return lux > TSL2550_MAX_LUX ? TSL2550_MAX_LUX : lux; -- 2.9.3 ``` ## Build Info ### ti-linux-kernel-dev ``` [pdp7@skylake ti-linux-kernel-dev]$ git log -1 --oneline 9c848e7 4.4.35-ti-r70 release [pdp7@skylake ti-linux-kernel-dev]$ git status On branch ti-linux-4.4.y Your branch is up-to-date with 'origin/ti-linux-4.4.y'. Changes not staged for commit: (use "git add <file>..." to update what will be committed) (use "git checkout -- <file>..." to discard changes in working directory) modified: patches/defconfig no changes added to commit (use "git add" and/or "git commit -a") [pdp7@skylake KERNEL]$ git status On branch v4.4.35-ti-r70 [pdp7@skylake KERNEL]$ git log --oneline -2 ./drivers/misc/tsl2550.c c23e541 tsl2550: fix lux1_input error in low light 14e51e5 misc: Drop owner assignment from i2c_driver ``` ### BeagleBone ``` root@beaglebone:~# cat /etc/dogtag BeagleBoard.org Debian Image 2016-08-14 root@beaglebone:~# cat /etc/debian_version 8.6 root@beaglebone:~# uname -a Linux beaglebone 4.4.35-ti-r70 #1 SMP Fri Dec 2 05:22:17 CST 2016 armv7l GNU/Linux ``` ## Example ### Low light in the room #### Before patch ``` root@beaglebone:~# cat /sys/devices/platform/ocp/4819c000.i2c/i2c-2/2-0039/lux1_input cat: /sys/devices/platform/ocp/4819c000.i2c/i2c-2/2-0039/lux1_input: Resource temporarily unavailable ``` ### After patch ``` root@beaglebone:~# cat /sys/devices/platform/ocp/4819c000.i2c/i2c-2/2-0039/lux1_input 0 ``` ## Smartphone backlight over sensor ``` root@beaglebone:~# cat /sys/devices/platform/ocp/4819c000.i2c/i2c-2/2-0039/lux1_input 364 ```
