linux-kernel - Re: [PATCH V4 2/2] i2c-designware: Add Intel Baytrail PMIC I2C bus support

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Date:	Thu, 22 Jan 2015 16:28:19 +0200
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	"David E. Box" <david.e.box@...ux.intel.com>
Cc:	wsa@...-dreams.de, jdelvare@...e.de, arnd@...db.de,
	maxime.ripard@...e-electrons.com, dianders@...omium.org,
	u.kleine-koenig@...gutronix.de,
	laurent.pinchart+renesas@...asonboard.com,
	boris.brezillon@...e-electrons.com, maxime.coquelin@...com,
	andrew@...n.ch, sjg@...omium.org, markus.mayer@...aro.org,
	ch.naveen@...sung.com, jacob.jun.pan@...ux.intel.com,
	max.schwarz@...ine.de, skuribay@...ox.com,
	Romain.Baeriswyl@...lis.com, wenkai.du@...el.com,
	christian.ruppert@...lis.com, alan@...ux.intel.com,
	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org
Subject: Re: [PATCH V4 2/2] i2c-designware: Add Intel Baytrail PMIC I2C bus
 support

On Thu, Jan 15, 2015 at 01:12:17AM -0800, David E. Box wrote:
> This patch implements an I2C bus sharing mechanism between the host and platform
> hardware on select Intel BayTrail SoC platforms using the X-Powers AXP288 PMIC.
> 
> On these platforms access to the PMIC must be shared with platform hardware. The
> hardware unit assumes full control of the I2C bus and the host must request
> access through a special semaphore. Hardware control of the bus also makes it
> necessary to disable runtime pm to avoid interfering with hardware transactions.
> 
> Signed-off-by: David E. Box <david.e.box@...ux.intel.com>

Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>

One comment, though:

> ---
>  drivers/i2c/busses/Kconfig                   |  11 ++
>  drivers/i2c/busses/Makefile                  |   1 +
>  drivers/i2c/busses/i2c-designware-baytrail.c | 160 +++++++++++++++++++++++++++
>  drivers/i2c/busses/i2c-designware-core.h     |   6 +
>  drivers/i2c/busses/i2c-designware-platdrv.c  |  20 +++-
>  5 files changed, 193 insertions(+), 5 deletions(-)
>  create mode 100644 drivers/i2c/busses/i2c-designware-baytrail.c
> 
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index 917c358..9a83c46 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -464,6 +464,17 @@ config I2C_DESIGNWARE_PCI
>  	  This driver can also be built as a module.  If so, the module
>  	  will be called i2c-designware-pci.
>  
> +config I2C_DESIGNWARE_BAYTRAIL
> +	bool "Intel Baytrail I2C semaphore support"

It would be nice if it was possible to compile this as a module.

> +	depends on I2C_DESIGNWARE_PLATFORM
> +	select IOSF_MBI
> +	help
> +	  This driver enables managed host access to the PMIC I2C bus on select
> +	  Intel BayTrail platforms using the X-Powers AXP288 PMIC. It allows
> +	  the host to request uninterrupted access to the PMIC's I2C bus from
> +	  the platform firmware controlling it. You should say Y if running on
> +	  a BayTrail system using the AXP288.
> +
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