From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:33924) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TfDFT-0004Wx-Vo for qemu-devel@nongnu.org; Sun, 02 Dec 2012 12:22:36 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TfDFS-00025i-R1 for qemu-devel@nongnu.org; Sun, 02 Dec 2012 12:22:35 -0500 Received: from mail-bk0-f45.google.com ([209.85.214.45]:59526) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TfDFS-00025b-JX for qemu-devel@nongnu.org; Sun, 02 Dec 2012 12:22:34 -0500 Received: by mail-bk0-f45.google.com with SMTP id jk13so680924bkc.4 for ; Sun, 02 Dec 2012 09:22:33 -0800 (PST) Message-ID: <50BB8E56.1050303@gmail.com> Date: Sun, 02 Dec 2012 18:22:30 +0100 From: Antoine Mathys MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] [PATCH 4/4] hw/ds1338.c: Handle stuck bits and preserve CH List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: peter.maydell@linaro.org, paul@codesourcery.com Preserve the CH bit when updating the time. Per the datasheet, some bits in the first eight registers must always read back as zero. These registers can be written in two ways: 1. By ourselves when we update the registers with the current time. 2. By user request Even though (1) is not supposed to set these bits it is safer to check anyway. In order not to duplicate this logic I thus chose to enforce it at read time. Note that currently we don't preserve what the user sends in (2). We will have to once we support stopping the clock (CH bit). Signed-off-by: Antoine Mathys --- hw/ds1338.c | 50 ++++++++++++++++++++++++++++++++++---------------- 1 file changed, 34 insertions(+), 16 deletions(-) diff --git a/hw/ds1338.c b/hw/ds1338.c index f3c6bc5..8f85635 100644 --- a/hw/ds1338.c +++ b/hw/ds1338.c @@ -40,17 +40,17 @@ static const VMStateDescription vmstate_ds1338 = { } }; -static void capture_current_time(DS1338State *s) +/* Write TM to the RTC registers. */ +static void write_time(DS1338State *s, const struct tm *tm) { - /* Capture the current time into the secondary registers - * which will be actually read by the data transfer operation. - */ - struct tm now; - qemu_get_timedate(&now, s->offset); - s->nvram[0] = to_bcd(now.tm_sec); - s->nvram[1] = to_bcd(now.tm_min); + /* Preserve the CH flag. */ + s->nvram[0] &= 0x80; + s->nvram[0] |= to_bcd(tm->tm_sec); + + s->nvram[1] = to_bcd(tm->tm_min); + if (s->nvram[2] & 0x40) { - int tmp = now.tm_hour; + int tmp = tm->tm_hour; if (tmp == 0) { tmp = 24; } @@ -60,12 +60,30 @@ static void capture_current_time(DS1338State *s) s->nvram[2] = 0x60 | to_bcd(tmp - 12); } } else { - s->nvram[2] = to_bcd(now.tm_hour); + s->nvram[2] = to_bcd(tm->tm_hour); } - s->nvram[3] = to_bcd(now.tm_wday + 1); - s->nvram[4] = to_bcd(now.tm_mday); - s->nvram[5] = to_bcd(now.tm_mon + 1); - s->nvram[6] = to_bcd(now.tm_year - 100); + s->nvram[3] = to_bcd(tm->tm_wday + 1); + s->nvram[4] = to_bcd(tm->tm_mday); + s->nvram[5] = to_bcd(tm->tm_mon + 1); + s->nvram[6] = to_bcd(tm->tm_year - 100); +} + +static void update_read_buffer(DS1338State *s) +{ + /* Capture the current time into the secondary registers + * which will be actually read by the data transfer operation. + */ + struct tm now; + qemu_get_timedate(&now, s->offset); + write_time(s, &now); + + /* Ensure specified bits read as zero. */ + s->nvram[1] &= 0x7F; + s->nvram[2] &= 0x7F; + s->nvram[3] &= 0x07; + s->nvram[4] &= 0x3F; + s->nvram[5] &= 0x1F; + s->nvram[7] &= 0xB3; } static void inc_regptr(DS1338State *s) @@ -76,7 +94,7 @@ static void inc_regptr(DS1338State *s) */ s->ptr = (s->ptr + 1) & (NVRAM_SIZE - 1); if (!s->ptr) { - capture_current_time(s); + update_read_buffer(s); } } @@ -91,7 +109,7 @@ static void ds1338_event(I2CSlave *i2c, enum i2c_event event) * START_SEND, because the guest can't get at that data * without going through a START_RECV which would overwrite it. */ - capture_current_time(s); + update_read_buffer(s); break; case I2C_START_SEND: s->addr_byte = true; -- 1.7.10.4