On Tue, Nov 11, 2014 at 12:32:56PM +0100, Wolfram Sang wrote: > On Tue, Sep 23, 2014 at 11:40:26AM -0700, 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. > > Can we foresee that other platforms will have similar mechanisms in the > future? > Maybe one other platform. Unlikely there'll be any others. Okay on your comments below. Dave > > +config I2C_BAYTRAIL_SEM > > I2C_DESIGNWARE_BAYTRAIL_SEM > > > + tristate "Intel Baytrail I2C semaphore support" > > + depends on I2C_DESIGNWARE_PLATFORM > > + select I2C_DESIGNWARE_CORE > > This select is already covered by I2C_DESIGNWARE_PLATFORM. > > > + select IOSF_MBI > > + help > > + This driver enables host access to the PMIC I2C bus on select Intel > > + BayTrail platforms using the X-Powers AXP288 PMIC. This driver is > > + required for host access to the PMIC on these platforms. You should > > + probably say Y if you have a BayTrail system, unless you know it uses > > + a different PMIC. Otherwises critical PMIC functions, like charging, > > + may not operate. > > + > > + This driver should be built as a m if I2C_DESIGNWARE_PLATFORM=m, > > + and as y if I2C_DESIGNWARE_PLATFORM=y. > > That shouldn't be the user's task to ensure. Please enforce this in the > makefile. Check Documentation/kbuid/makefiles.txt, Section 3.3. > > > --- /dev/null > > +++ b/drivers/i2c/busses/i2c-baytrail-sem.c > > @@ -0,0 +1,157 @@ > > +/* > > + * Intel BayTrail PMIC I2C bus semaphore implementaion > > + * Copyright (c) 2014, Intel Corporation. > > Mika, can you have a look at the ACPI part here? > > > diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h > > index d66b6cb..13e0809 100644 > > --- a/drivers/i2c/busses/i2c-designware-core.h > > +++ b/drivers/i2c/busses/i2c-designware-core.h > > @@ -65,6 +65,8 @@ > > * @ss_lcnt: standard speed LCNT value > > * @fs_hcnt: fast speed HCNT value > > * @fs_lcnt: fast speed LCNT value > > + * has_hw_lock: true if bus access requires hardware lock > > + * pm_runtime_disabled: true if pm runtime is disabled > > Look closely. There is a difference to the entries above. > > > @@ -123,3 +127,18 @@ extern void i2c_dw_disable(struct dw_i2c_dev *dev); > > extern void i2c_dw_clear_int(struct dw_i2c_dev *dev); > > extern void i2c_dw_disable_int(struct dw_i2c_dev *dev); > > extern u32 i2c_dw_read_comp_param(struct dw_i2c_dev *dev); > > + > > +#if IS_ENABLED(CONFIG_I2C_BAYTRAIL_SEM) > > +extern int baytrail_i2c_acquire(struct dw_i2c_dev *dev); > > +extern void baytrail_i2c_release(struct dw_i2c_dev *dev); > > +extern void baytrail_evaluate_sem(struct dw_i2c_dev *dev); > > +#define i2c_dw_acquire_ownership(dev) baytrail_i2c_acquire(dev) > > +#define i2c_dw_release_ownership(dev) baytrail_i2c_release(dev) > > +#define i2c_dw_eval_lock(dev) baytrail_evaluate_sem(dev) > i2c_dw_test_ownership_support()? > > That doesn't scale in case other platformts will need this. I could > imagine a struct i2c_dw_ownership_ops() (or whatever name) which gets > populated according to the matched device. > > Thanks, > > Wolfram > -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
