diff mbox series

[v5,01/36] i2c: tegra: Make tegra_i2c_flush_fifos() usable in atomic transfer

Message ID 20200906185039.22700-2-digetx@gmail.com
State Superseded
Headers show
Series Improvements for Tegra I2C driver | expand

Commit Message

Dmitry Osipenko Sept. 6, 2020, 6:50 p.m. UTC 
The tegra_i2c_flush_fifos() shouldn't sleep in atomic transfer and jiffies
are not updating if interrupts are disabled. Let's switch to use iopoll
API helpers for register-polling. The iopoll API provides helpers for both
atomic and non-atomic cases.

Note that this patch doesn't fix any known problem because normally FIFO
is flushed at the time of starting a new transfer.

Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/i2c/busses/i2c-tegra.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

Comments

Andy Shevchenko Sept. 7, 2020, 7:56 a.m. UTC | #1 
On Sun, Sep 6, 2020 at 9:51 PM Dmitry Osipenko <digetx@gmail.com> wrote:
>
> The tegra_i2c_flush_fifos() shouldn't sleep in atomic transfer and jiffies
> are not updating if interrupts are disabled. Let's switch to use iopoll
> API helpers for register-polling. The iopoll API provides helpers for both
> atomic and non-atomic cases.
>
> Note that this patch doesn't fix any known problem because normally FIFO
> is flushed at the time of starting a new transfer.

...

> +       if (i2c_dev->is_curr_atomic_xfer)
> +               err = readl_relaxed_poll_timeout_atomic(addr, val, !(val & mask),
> +                                                       1000, 1000000);
> +       else
> +               err = readl_relaxed_poll_timeout(addr, val, !(val & mask),
> +                                                1000, 1000000);
> +
> +       if (err) {
> +               dev_err(i2c_dev->dev, "failed to flush FIFO\n");

> +               return err;
>         }
>         return 0;

return err; ?
Dmitry Osipenko Sept. 7, 2020, 2:31 p.m. UTC | #2 
07.09.2020 10:56, Andy Shevchenko пишет:
> On Sun, Sep 6, 2020 at 9:51 PM Dmitry Osipenko <digetx@gmail.com> wrote:
>>
>> The tegra_i2c_flush_fifos() shouldn't sleep in atomic transfer and jiffies
>> are not updating if interrupts are disabled. Let's switch to use iopoll
>> API helpers for register-polling. The iopoll API provides helpers for both
>> atomic and non-atomic cases.
>>
>> Note that this patch doesn't fix any known problem because normally FIFO
>> is flushed at the time of starting a new transfer.
> 
> ...
> 
>> +       if (i2c_dev->is_curr_atomic_xfer)
>> +               err = readl_relaxed_poll_timeout_atomic(addr, val, !(val & mask),
>> +                                                       1000, 1000000);
>> +       else
>> +               err = readl_relaxed_poll_timeout(addr, val, !(val & mask),
>> +                                                1000, 1000000);
>> +
>> +       if (err) {
>> +               dev_err(i2c_dev->dev, "failed to flush FIFO\n");
> 
>> +               return err;
>>         }
>>         return 0;
> 
> return err; ?
> 

The return 0 is intentional here because returned "err" implies that
error happened and error code is returned, while 0 explicitly shows the
success status. Hence it's always cleaner and more expressive to
directly return 0 on success, IMO. I'd prefer to keep this part as-is.
diff mbox series

Patch

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 00d3e4d7a01e..ab88cdd70376 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -470,9 +470,9 @@  static int tegra_i2c_init_dma(struct tegra_i2c_dev *i2c_dev)
 
 static int tegra_i2c_flush_fifos(struct tegra_i2c_dev *i2c_dev)
 {
-	unsigned long timeout = jiffies + HZ;
-	unsigned int offset;
-	u32 mask, val;
+	u32 mask, val, offset, reg_offset;
+	void __iomem *addr;
+	int err;
 
 	if (i2c_dev->hw->has_mst_fifo) {
 		mask = I2C_MST_FIFO_CONTROL_TX_FLUSH |
@@ -488,12 +488,19 @@  static int tegra_i2c_flush_fifos(struct tegra_i2c_dev *i2c_dev)
 	val |= mask;
 	i2c_writel(i2c_dev, val, offset);
 
-	while (i2c_readl(i2c_dev, offset) & mask) {
-		if (time_after(jiffies, timeout)) {
-			dev_warn(i2c_dev->dev, "timeout waiting for fifo flush\n");
-			return -ETIMEDOUT;
-		}
-		usleep_range(1000, 2000);
+	reg_offset = tegra_i2c_reg_addr(i2c_dev, offset);
+	addr = i2c_dev->base + reg_offset;
+
+	if (i2c_dev->is_curr_atomic_xfer)
+		err = readl_relaxed_poll_timeout_atomic(addr, val, !(val & mask),
+							1000, 1000000);
+	else
+		err = readl_relaxed_poll_timeout(addr, val, !(val & mask),
+						 1000, 1000000);
+
+	if (err) {
+		dev_err(i2c_dev->dev, "failed to flush FIFO\n");
+		return err;
 	}
 	return 0;
 }