Hi Lucas, Wolfram,
On Thu, 2018-03-08 at 14:25 +0100, Lucas Stach wrote:
> Instead of repeatedly calling clk_get_rate for each transfer, register
> a clock notifier to update the cached divider value each time the clock
> rate actually changes.
>
> Signed-off-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> ---
> v2: Don't use a static notifier block, as this is unsafe with multiple
> i2c-imx driver instances.
This removes the need to lock the clk_prepare mutex with every i2c
transfer just to check the rate of a clock that never changes on many
systems.
With the embedded notifier block this now looks safe to handle unlikely
changes of the i2c module clock.
Reviewed-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
regards
Philipp
> ---
> drivers/i2c/busses/i2c-imx.c | 32 +++++++++++++++++++++++++-------
> 1 file changed, 25 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 999557729ad2..c9632b2f0eaa 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -194,6 +194,7 @@ struct imx_i2c_dma {
> struct imx_i2c_struct {
> struct i2c_adapter adapter;
> struct clk *clk;
> + struct notifier_block clk_change_nb;
> void __iomem *base;
> wait_queue_head_t queue;
> unsigned long i2csr;
> @@ -467,15 +468,14 @@ static int i2c_imx_acked(struct imx_i2c_struct *i2c_imx)
> return 0;
> }
>
> -static void i2c_imx_set_clk(struct imx_i2c_struct *i2c_imx)
> +static void i2c_imx_set_clk(struct imx_i2c_struct *i2c_imx,
> + unsigned int i2c_clk_rate)
> {
> struct imx_i2c_clk_pair *i2c_clk_div = i2c_imx->hwdata->clk_div;
> - unsigned int i2c_clk_rate;
> unsigned int div;
> int i;
>
> /* Divider value calculation */
> - i2c_clk_rate = clk_get_rate(i2c_imx->clk);
> if (i2c_imx->cur_clk == i2c_clk_rate)
> return;
>
> @@ -510,6 +510,20 @@ static void i2c_imx_set_clk(struct imx_i2c_struct *i2c_imx)
> #endif
> }
>
> +static int i2c_imx_clk_notifier_call(struct notifier_block *nb,
> + unsigned long action, void *data)
> +{
> + struct clk_notifier_data *ndata = data;
> + struct imx_i2c_struct *i2c_imx = container_of(&ndata->clk,
> + struct imx_i2c_struct,
> + clk);
> +
> + if (action & POST_RATE_CHANGE)
> + i2c_imx_set_clk(i2c_imx, ndata->new_rate);
> +
> + return NOTIFY_OK;
> +}
> +
> static int i2c_imx_start(struct imx_i2c_struct *i2c_imx)
> {
> unsigned int temp = 0;
> @@ -517,8 +531,6 @@ static int i2c_imx_start(struct imx_i2c_struct *i2c_imx)
>
> dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);
>
> - i2c_imx_set_clk(i2c_imx);
> -
> imx_i2c_write_reg(i2c_imx->ifdr, i2c_imx, IMX_I2C_IFDR);
> /* Enable I2C controller */
> imx_i2c_write_reg(i2c_imx->hwdata->i2sr_clr_opcode, i2c_imx, IMX_I2C_I2SR);
> @@ -1131,6 +1143,9 @@ static int i2c_imx_probe(struct platform_device *pdev)
> "clock-frequency", &i2c_imx->bitrate);
> if (ret < 0 && pdata && pdata->bitrate)
> i2c_imx->bitrate = pdata->bitrate;
> + i2c_imx->clk_change_nb.notifier_call = i2c_imx_clk_notifier_call;
> + clk_notifier_register(i2c_imx->clk, &i2c_imx->clk_change_nb);
> + i2c_imx_set_clk(i2c_imx, clk_get_rate(i2c_imx->clk));
>
> /* Set up chip registers to defaults */
> imx_i2c_write_reg(i2c_imx->hwdata->i2cr_ien_opcode ^ I2CR_IEN,
> @@ -1141,12 +1156,12 @@ static int i2c_imx_probe(struct platform_device *pdev)
> ret = i2c_imx_init_recovery_info(i2c_imx, pdev);
> /* Give it another chance if pinctrl used is not ready yet */
> if (ret == -EPROBE_DEFER)
> - goto rpm_disable;
> + goto clk_notifier_unregister;
>
> /* Add I2C adapter */
> ret = i2c_add_numbered_adapter(&i2c_imx->adapter);
> if (ret < 0)
> - goto rpm_disable;
> + goto clk_notifier_unregister;
>
> pm_runtime_mark_last_busy(&pdev->dev);
> pm_runtime_put_autosuspend(&pdev->dev);
> @@ -1162,6 +1177,8 @@ static int i2c_imx_probe(struct platform_device *pdev)
>
> return 0; /* Return OK */
>
> +clk_notifier_unregister:
> + clk_notifier_unregister(i2c_imx->clk, &i2c_imx->clk_change_nb);
> rpm_disable:
> pm_runtime_put_noidle(&pdev->dev);
> pm_runtime_disable(&pdev->dev);
> @@ -1195,6 +1212,7 @@ static int i2c_imx_remove(struct platform_device *pdev)
> imx_i2c_write_reg(0, i2c_imx, IMX_I2C_I2CR);
> imx_i2c_write_reg(0, i2c_imx, IMX_I2C_I2SR);
>
> + clk_notifier_unregister(i2c_imx->clk, &i2c_imx->clk_change_nb);
> clk_disable_unprepare(i2c_imx->clk);
>
> pm_runtime_put_noidle(&pdev->dev);
