diff options
Diffstat (limited to 'target/linux/brcm2708/patches-4.9/950-0110-i2c-bcm2835-Add-support-for-Repeated-Start-Condition.patch')
| -rw-r--r-- | target/linux/brcm2708/patches-4.9/950-0110-i2c-bcm2835-Add-support-for-Repeated-Start-Condition.patch | 181 |
1 files changed, 0 insertions, 181 deletions
diff --git a/target/linux/brcm2708/patches-4.9/950-0110-i2c-bcm2835-Add-support-for-Repeated-Start-Condition.patch b/target/linux/brcm2708/patches-4.9/950-0110-i2c-bcm2835-Add-support-for-Repeated-Start-Condition.patch deleted file mode 100644 index 9ae16e426a..0000000000 --- a/target/linux/brcm2708/patches-4.9/950-0110-i2c-bcm2835-Add-support-for-Repeated-Start-Condition.patch +++ /dev/null @@ -1,181 +0,0 @@ -From db656eb11aebb0d7e4b833f9b452503ddb1351f1 Mon Sep 17 00:00:00 2001 -From: =?UTF-8?q?Noralf=20Tr=C3=B8nnes?= <noralf@tronnes.org> -Date: Fri, 23 Sep 2016 04:54:27 +0200 -Subject: [PATCH] i2c: bcm2835: Add support for Repeated Start Condition -MIME-Version: 1.0 -Content-Type: text/plain; charset=UTF-8 -Content-Transfer-Encoding: 8bit - -Documentation/i2c/i2c-protocol states that Combined transactions should -separate messages with a Start bit and end the whole transaction with a -Stop bit. This patch adds support for issuing only a Start between -messages instead of a Stop followed by a Start. - -This implementation differs from downstream i2c-bcm2708 in 2 respects: -- it uses an interrupt to detect that the transfer is active instead - of using polling. There is no interrupt for Transfer Active, but by - not prefilling the FIFO it's possible to use the TXW interrupt. -- when resetting/disabling the controller between transfers it writes - CLEAR to the control register instead of just zero. - Using just zero gave many errors. This might be the reason why - downstream had to disable this feature and make it available with a - module parameter. - -I have run thousands of transfers to a DS1307 (rtc), MMA8451 (accel) -and AT24C32 (eeprom) in parallel without problems. - -Signed-off-by: Noralf Trønnes <noralf@tronnes.org> -Acked-by: Eric Anholt <eric@anholt.net> ---- - drivers/i2c/busses/i2c-bcm2835.c | 101 ++++++++++++++++++++++++--------------- - 1 file changed, 63 insertions(+), 38 deletions(-) - ---- a/drivers/i2c/busses/i2c-bcm2835.c -+++ b/drivers/i2c/busses/i2c-bcm2835.c -@@ -63,6 +63,7 @@ struct bcm2835_i2c_dev { - struct i2c_adapter adapter; - struct completion completion; - struct i2c_msg *curr_msg; -+ int num_msgs; - u32 msg_err; - u8 *msg_buf; - size_t msg_buf_remaining; -@@ -110,6 +111,45 @@ static void bcm2835_drain_rxfifo(struct - } - - /* -+ * Repeated Start Condition (Sr) -+ * The BCM2835 ARM Peripherals datasheet mentions a way to trigger a Sr when it -+ * talks about reading from a slave with 10 bit address. This is achieved by -+ * issuing a write, poll the I2CS.TA flag and wait for it to be set, and then -+ * issue a read. -+ * A comment in https://github.com/raspberrypi/linux/issues/254 shows how the -+ * firmware actually does it using polling and says that it's a workaround for -+ * a problem in the state machine. -+ * It turns out that it is possible to use the TXW interrupt to know when the -+ * transfer is active, provided the FIFO has not been prefilled. -+ */ -+ -+static void bcm2835_i2c_start_transfer(struct bcm2835_i2c_dev *i2c_dev) -+{ -+ u32 c = BCM2835_I2C_C_ST | BCM2835_I2C_C_I2CEN; -+ struct i2c_msg *msg = i2c_dev->curr_msg; -+ bool last_msg = (i2c_dev->num_msgs == 1); -+ -+ if (!i2c_dev->num_msgs) -+ return; -+ -+ i2c_dev->num_msgs--; -+ i2c_dev->msg_buf = msg->buf; -+ i2c_dev->msg_buf_remaining = msg->len; -+ -+ if (msg->flags & I2C_M_RD) -+ c |= BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR; -+ else -+ c |= BCM2835_I2C_C_INTT; -+ -+ if (last_msg) -+ c |= BCM2835_I2C_C_INTD; -+ -+ bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr); -+ bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len); -+ bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c); -+} -+ -+/* - * Note about I2C_C_CLEAR on error: - * The I2C_C_CLEAR on errors will take some time to resolve -- if you were in - * non-idle state and I2C_C_READ, it sets an abort_rx flag and runs through -@@ -153,6 +193,12 @@ static irqreturn_t bcm2835_i2c_isr(int t - } - - bcm2835_fill_txfifo(i2c_dev); -+ -+ if (i2c_dev->num_msgs && !i2c_dev->msg_buf_remaining) { -+ i2c_dev->curr_msg++; -+ bcm2835_i2c_start_transfer(i2c_dev); -+ } -+ - return IRQ_HANDLED; - } - -@@ -177,30 +223,25 @@ complete: - return IRQ_HANDLED; - } - --static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev, -- struct i2c_msg *msg) -+static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], -+ int num) - { -- u32 c; -+ struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap); - unsigned long time_left; -+ int i; - -- i2c_dev->curr_msg = msg; -- i2c_dev->msg_buf = msg->buf; -- i2c_dev->msg_buf_remaining = msg->len; -- reinit_completion(&i2c_dev->completion); -- -- bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR); -+ for (i = 0; i < (num - 1); i++) -+ if (msgs[i].flags & I2C_M_RD) { -+ dev_warn_once(i2c_dev->dev, -+ "only one read message supported, has to be last\n"); -+ return -EOPNOTSUPP; -+ } - -- if (msg->flags & I2C_M_RD) { -- c = BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR; -- } else { -- c = BCM2835_I2C_C_INTT; -- bcm2835_fill_txfifo(i2c_dev); -- } -- c |= BCM2835_I2C_C_ST | BCM2835_I2C_C_INTD | BCM2835_I2C_C_I2CEN; -+ i2c_dev->curr_msg = msgs; -+ i2c_dev->num_msgs = num; -+ reinit_completion(&i2c_dev->completion); - -- bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr); -- bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len); -- bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c); -+ bcm2835_i2c_start_transfer(i2c_dev); - - time_left = wait_for_completion_timeout(&i2c_dev->completion, - BCM2835_I2C_TIMEOUT); -@@ -211,31 +252,15 @@ static int bcm2835_i2c_xfer_msg(struct b - return -ETIMEDOUT; - } - -- if (likely(!i2c_dev->msg_err)) -- return 0; -+ if (!i2c_dev->msg_err) -+ return num; - - dev_dbg(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err); - - if (i2c_dev->msg_err & BCM2835_I2C_S_ERR) - return -EREMOTEIO; -- else -- return -EIO; --} -- --static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], -- int num) --{ -- struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap); -- int i; -- int ret = 0; -- -- for (i = 0; i < num; i++) { -- ret = bcm2835_i2c_xfer_msg(i2c_dev, &msgs[i]); -- if (ret) -- break; -- } - -- return ret ?: i; -+ return -EIO; - } - - static u32 bcm2835_i2c_func(struct i2c_adapter *adap) |