Re: [RFC PATCH v2 2/7] i2c: core: use I2C locking behaviour also for SMBUS

From: Simon Horman <horms@verge.net.au>
To: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: linux-i2c@vger.kernel.org, Tero Kristo <t-kristo@ti.com>,
	Phil Reid <preid@electromag.com.au>,
	Tony Lindgren <tony@atomide.com>, Keerthy <j-keerthy@ti.com>,
	linux-kernel@vger.kernel.org,
	Russell King <linux@armlinux.org.uk>,
	linux-renesas-soc@vger.kernel.org, linux-omap@vger.kernel.org,
	linux-tegra@vger.kernel.org,
	Stefan Lengfeld <contact@stefanchrist.eu>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Peter Rosin <peda@axentia.se>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH v2 2/7] i2c: core: use I2C locking behaviour also for SMBUS
Date: Fri, 15 Mar 2019 13:17:22 +0100	[thread overview]
Message-ID: <20190315121722.w4fhr4zpxosutpbh@verge.net.au> (raw)
In-Reply-To: <20190302134735.4393-3-wsa+renesas@sang-engineering.com>

On Sat, Mar 02, 2019 at 02:47:30PM +0100, Wolfram Sang wrote:
> If I2C transfers are executed in atomic contexts, trylock is used
> instead of lock. This behaviour was missing for SMBUS, although a lot of
> transfers are of SMBUS type, either emulated or direct. So, factor out
> the locking routine into a helper and use it for I2C and SMBUS.
> 
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> Acked-by: Peter Rosin <peda@axentia.se>
> Acked-by: Tony Lindgren <tony@atomide.com>

Reviewed-by: Simon Horman <horms+renesas@verge.net.au>

> ---
>  drivers/i2c/i2c-core-base.c  | 11 +++--------
>  drivers/i2c/i2c-core-smbus.c |  7 ++++++-
>  drivers/i2c/i2c-core.h       | 12 ++++++++++++
>  3 files changed, 21 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index cb6c5cb0df0b..004f8a3b6365 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -1946,14 +1946,9 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
>  	 *    one (discarding status on the second message) or errno
>  	 *    (discarding status on the first one).
>  	 */
> -	if (in_atomic() || irqs_disabled()) {
> -		ret = i2c_trylock_bus(adap, I2C_LOCK_SEGMENT);
> -		if (!ret)
> -			/* I2C activity is ongoing. */
> -			return -EAGAIN;
> -	} else {
> -		i2c_lock_bus(adap, I2C_LOCK_SEGMENT);
> -	}
> +	ret = __i2c_lock_bus_helper(adap);
> +	if (ret)
> +		return ret;
>  
>  	ret = __i2c_transfer(adap, msgs, num);
>  	i2c_unlock_bus(adap, I2C_LOCK_SEGMENT);
> diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
> index 132119112596..357e083e8f45 100644
> --- a/drivers/i2c/i2c-core-smbus.c
> +++ b/drivers/i2c/i2c-core-smbus.c
> @@ -20,6 +20,8 @@
>  #include <linux/i2c-smbus.h>
>  #include <linux/slab.h>
>  
> +#include "i2c-core.h"
> +
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/smbus.h>
>  
> @@ -530,7 +532,10 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr,
>  {
>  	s32 res;
>  
> -	i2c_lock_bus(adapter, I2C_LOCK_SEGMENT);
> +	res = __i2c_lock_bus_helper(adapter);
> +	if (res)
> +		return res;
> +
>  	res = __i2c_smbus_xfer(adapter, addr, flags, read_write,
>  			       command, protocol, data);
>  	i2c_unlock_bus(adapter, I2C_LOCK_SEGMENT);
> diff --git a/drivers/i2c/i2c-core.h b/drivers/i2c/i2c-core.h
> index 37576f50fe20..6e98aa811980 100644
> --- a/drivers/i2c/i2c-core.h
> +++ b/drivers/i2c/i2c-core.h
> @@ -29,6 +29,18 @@ extern int		__i2c_first_dynamic_bus_num;
>  
>  int i2c_check_7bit_addr_validity_strict(unsigned short addr);
>  
> +static inline int __i2c_lock_bus_helper(struct i2c_adapter *adap)
> +{
> +	int ret = 0;
> +
> +	if (in_atomic() || irqs_disabled())
> +		ret = i2c_trylock_bus(adap, I2C_LOCK_SEGMENT) ? 0 : -EAGAIN;
> +	else
> +		i2c_lock_bus(adap, I2C_LOCK_SEGMENT);
> +
> +	return ret;
> +}
> +
>  #ifdef CONFIG_ACPI
>  const struct acpi_device_id *
>  i2c_acpi_match_device(const struct acpi_device_id *matches,
> -- 
> 2.11.0
> 
> 
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