| Message ID | 20200908224006.25636-18-digetx@gmail.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Improvements for Tegra I2C driver | expand |
On Wed, Sep 09, 2020 at 01:39:49AM +0300, Dmitry Osipenko wrote: > The barrier() was intended to reduce possibility of racing with the > interrupt handler, but driver's code evolved significantly and today's > driver enables interrupt only when it waits for completion notification. > Hence barrier() has no good use anymore, let's remove it. > > Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> > Signed-off-by: Dmitry Osipenko <digetx@gmail.com> > --- > drivers/i2c/busses/i2c-tegra.c | 13 +++++-------- > 1 file changed, 5 insertions(+), 8 deletions(-) Acked-by: Thierry Reding <treding@nvidia.com>
On Wed, 09 Sep 2020 01:39:49 +0300, Dmitry Osipenko wrote: > The barrier() was intended to reduce possibility of racing with the > interrupt handler, but driver's code evolved significantly and today's > driver enables interrupt only when it waits for completion notification. > Hence barrier() has no good use anymore, let's remove it. > > Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> > Signed-off-by: Dmitry Osipenko <digetx@gmail.com> > Acked-by: Thierry Reding <treding@nvidia.com> > --- > drivers/i2c/busses/i2c-tegra.c | 13 +++++-------- > 1 file changed, 5 insertions(+), 8 deletions(-) Tested-by: Thierry Reding <treding@nvidia.com>
diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c index 71e82a68c942..ab83d1de6c94 100644 --- a/drivers/i2c/busses/i2c-tegra.c +++ b/drivers/i2c/busses/i2c-tegra.c @@ -795,18 +795,17 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev) words_to_transfer = tx_fifo_avail; /* - * Update state before writing to FIFO. If this casues us - * to finish writing all bytes (AKA buf_remaining goes to 0) we - * have a potential for an interrupt (PACKET_XFER_COMPLETE is - * not maskable). We need to make sure that the isr sees - * buf_remaining as 0 and doesn't call us back re-entrantly. + * Update state before writing to FIFO. Note that this may + * cause us to finish writing all bytes (AKA buf_remaining + * goes to 0), hence we have a potential for an interrupt + * (PACKET_XFER_COMPLETE is not maskable), but GIC interrupt + * is disabled at this point. */ buf_remaining -= words_to_transfer * BYTES_PER_FIFO_WORD; tx_fifo_avail -= words_to_transfer; i2c_dev->msg_buf_remaining = buf_remaining; i2c_dev->msg_buf = buf + words_to_transfer * BYTES_PER_FIFO_WORD; - barrier(); i2c_writesl(i2c_dev, buf, I2C_TX_FIFO, words_to_transfer); @@ -827,10 +826,8 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev) memcpy(&val, buf, buf_remaining); val = le32_to_cpu(val); - /* Again update before writing to FIFO to make sure isr sees. */ i2c_dev->msg_buf_remaining = 0; i2c_dev->msg_buf = NULL; - barrier(); i2c_writel(i2c_dev, val, I2C_TX_FIFO); }