From ab135622cf478585bdfcb68b85e4a817d74a0c42 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Tue, 17 Nov 2020 12:56:33 +0000 Subject: tmp105: Correct handling of temperature limit checks MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The TMP105 datasheet says that in Interrupt Mode (when TM==1) the device signals an alert when the temperature equals or exceeds the T_high value and then remains high until a device register is read or the device responds to the SMBUS Alert Response address, or the device is put into Shutdown Mode. Thereafter the Alert pin will only be re-signalled when temperature falls below T_low; alert can then be cleared in the same set of ways, and the device returns to its initial "alert when temperature goes above T_high" mode. (If this textual description is confusing, see figure 3 in the TI datasheet at https://www.ti.com/lit/gpn/tmp105 .) We were misimplementing this as a simple "always alert if temperature is above T_high or below T_low" condition, which gives a spurious alert on startup if using the "T_high = 80 degrees C, T_low = 75 degrees C" reset limit values. Implement the correct (hysteresis) behaviour by tracking whether we are currently looking for the temperature to rise over T_high or for it to fall below T_low. Our implementation of the comparator mode (TM==0) wasn't wrong, but rephrase it to match the way that interrupt mode is now handled for clarity. Signed-off-by: Peter Maydell Reviewed-by: Cédric Le Goater Message-id: 20201110150023.25533-3-peter.maydell@linaro.org --- hw/misc/tmp105.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 61 insertions(+), 9 deletions(-) (limited to 'hw/misc/tmp105.c') diff --git a/hw/misc/tmp105.c b/hw/misc/tmp105.c index 0a4aad4854..d299d9b21b 100644 --- a/hw/misc/tmp105.c +++ b/hw/misc/tmp105.c @@ -41,16 +41,40 @@ static void tmp105_alarm_update(TMP105State *s) return; } - if ((s->config >> 1) & 1) { /* TM */ - if (s->temperature >= s->limit[1]) - s->alarm = 1; - else if (s->temperature < s->limit[0]) - s->alarm = 1; + if (s->config >> 1 & 1) { + /* + * TM == 1 : Interrupt mode. We signal Alert when the + * temperature rises above T_high, and expect the guest to clear + * it (eg by reading a device register). + */ + if (s->detect_falling) { + if (s->temperature < s->limit[0]) { + s->alarm = 1; + s->detect_falling = false; + } + } else { + if (s->temperature >= s->limit[1]) { + s->alarm = 1; + s->detect_falling = true; + } + } } else { - if (s->temperature >= s->limit[1]) - s->alarm = 1; - else if (s->temperature < s->limit[0]) - s->alarm = 0; + /* + * TM == 0 : Comparator mode. We signal Alert when the temperature + * rises above T_high, and stop signalling it when the temperature + * falls below T_low. + */ + if (s->detect_falling) { + if (s->temperature < s->limit[0]) { + s->alarm = 0; + s->detect_falling = false; + } + } else { + if (s->temperature >= s->limit[1]) { + s->alarm = 1; + s->detect_falling = true; + } + } } tmp105_interrupt_update(s); @@ -197,6 +221,29 @@ static int tmp105_post_load(void *opaque, int version_id) return 0; } +static bool detect_falling_needed(void *opaque) +{ + TMP105State *s = opaque; + + /* + * We only need to migrate the detect_falling bool if it's set; + * for migration from older machines we assume that it is false + * (ie temperature is not out of range). + */ + return s->detect_falling; +} + +static const VMStateDescription vmstate_tmp105_detect_falling = { + .name = "TMP105/detect-falling", + .version_id = 1, + .minimum_version_id = 1, + .needed = detect_falling_needed, + .fields = (VMStateField[]) { + VMSTATE_BOOL(detect_falling, TMP105State), + VMSTATE_END_OF_LIST() + } +}; + static const VMStateDescription vmstate_tmp105 = { .name = "TMP105", .version_id = 0, @@ -212,6 +259,10 @@ static const VMStateDescription vmstate_tmp105 = { VMSTATE_UINT8(alarm, TMP105State), VMSTATE_I2C_SLAVE(i2c, TMP105State), VMSTATE_END_OF_LIST() + }, + .subsections = (const VMStateDescription*[]) { + &vmstate_tmp105_detect_falling, + NULL } }; @@ -224,6 +275,7 @@ static void tmp105_reset(I2CSlave *i2c) s->config = 0; s->faults = tmp105_faultq[(s->config >> 3) & 3]; s->alarm = 0; + s->detect_falling = false; s->limit[0] = 0x4b00; /* T_LOW, 75 degrees C */ s->limit[1] = 0x5000; /* T_HIGH, 80 degrees C */ -- cgit v1.2.3