lkml.org 
[lkml]   [2014]   [Nov]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH V2] i2c-designware: Add Intel Baytrail PMIC I2C bus support
    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
    >




    \
     
     \ /
      Last update: 2014-11-11 18:41    [W:5.039 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site