diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c index 565ef69ce614..241e08ae7c27 100644 --- 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; @@ -109,6 +110,45 @@ static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev) } } +/* + * 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 @@ -151,6 +191,12 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data) } 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; } @@ -175,30 +221,25 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data) 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; + 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; + } + + i2c_dev->curr_msg = msgs; + i2c_dev->num_msgs = num; reinit_completion(&i2c_dev->completion); - bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR); - - 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; - - 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); @@ -209,31 +250,15 @@ static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev, 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)