2018-04-10 13:02:05

by Jia-Ju Bai

Subject: [PATCH] platform: x86: intel_scu_ipc: Replace mdelay with usleep_range in intel_scu_ipc_i2c_cntrl

intel_scu_ipc_i2c_cntrl() calls mutex_lock(), which indicates
this function is not called in atomic context.

Despite never getting called from atomic context,
intel_scu_ipc_i2c_cntrl() calls mdelay to busily wait.
This is not necessary and can be replaced with usleep_range to
avoid busy waiting.

This is found by a static analysis tool named DCNS written by myself.
And I also manually check it.

Signed-off-by: Jia-Ju Bai <[email protected]>
---
drivers/platform/x86/intel_scu_ipc.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/x86/intel_scu_ipc.c b/drivers/platform/x86/intel_scu_ipc.c
index 2c85f75..75c8fef 100644
--- a/drivers/platform/x86/intel_scu_ipc.c
+++ b/drivers/platform/x86/intel_scu_ipc.c
@@ -584,11 +584,11 @@ int intel_scu_ipc_i2c_cntrl(u32 addr, u32 *data)
if (cmd == IPC_I2C_READ) {
writel(addr, scu->i2c_base + IPC_I2C_CNTRL_ADDR);
/* Write not getting updated without delay */
- mdelay(1);
+ usleep_range(1000, 2000);
*data = readl(scu->i2c_base + I2C_DATA_ADDR);
} else if (cmd == IPC_I2C_WRITE) {
writel(*data, scu->i2c_base + I2C_DATA_ADDR);
- mdelay(1);
+ usleep_range(1000, 2000);
writel(addr, scu->i2c_base + IPC_I2C_CNTRL_ADDR);
} else {
dev_err(scu->dev,
--
1.9.1

2018-04-10 15:32:22

by Andy Shevchenko

Subject: Re: [PATCH] platform: x86: intel_scu_ipc: Replace mdelay with usleep_range in intel_scu_ipc_i2c_cntrl

On Tue, Apr 10, 2018 at 3:57 PM, Jia-Ju Bai <[email protected]> wrote:
> intel_scu_ipc_i2c_cntrl() calls mutex_lock(), which indicates
> this function is not called in atomic context.
>
> Despite never getting called from atomic context,
> intel_scu_ipc_i2c_cntrl() calls mdelay to busily wait.
> This is not necessary and can be replaced with usleep_range to
> avoid busy waiting.
>
> This is found by a static analysis tool named DCNS written by myself.
> And I also manually check it.

I'm not sure we even need that delay at all.
Anyway, pushed to my review and testing queue, thanks!

>
> Signed-off-by: Jia-Ju Bai <[email protected]>
> ---
> drivers/platform/x86/intel_scu_ipc.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/platform/x86/intel_scu_ipc.c b/drivers/platform/x86/intel_scu_ipc.c
> index 2c85f75..75c8fef 100644
> --- a/drivers/platform/x86/intel_scu_ipc.c
> +++ b/drivers/platform/x86/intel_scu_ipc.c
> @@ -584,11 +584,11 @@ int intel_scu_ipc_i2c_cntrl(u32 addr, u32 *data)
> if (cmd == IPC_I2C_READ) {
> writel(addr, scu->i2c_base + IPC_I2C_CNTRL_ADDR);
> /* Write not getting updated without delay */
> - mdelay(1);
> + usleep_range(1000, 2000);
> *data = readl(scu->i2c_base + I2C_DATA_ADDR);
> } else if (cmd == IPC_I2C_WRITE) {
> writel(*data, scu->i2c_base + I2C_DATA_ADDR);
> - mdelay(1);
> + usleep_range(1000, 2000);
> writel(addr, scu->i2c_base + IPC_I2C_CNTRL_ADDR);
> } else {
> dev_err(scu->dev,
> --
> 1.9.1
>



--
With Best Regards,
Andy Shevchenko