linux-kernel - Re: [PATCH v3 35/36] platform/x86: intel_pmc

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Message-ID: <20200120092650.GI2665@lahna.fi.intel.com>
Date:   Mon, 20 Jan 2020 11:26:50 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Darren Hart <dvhart@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Zha Qipeng <qipeng.zha@...el.com>,
        "David E . Box" <david.e.box@...ux.intel.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 35/36] platform/x86: intel_pmc_ipc: Convert to MFD

On Fri, Jan 17, 2020 at 11:32:02AM +0000, Lee Jones wrote:
> [...]
> 
> > > Looks like Regmap could save you the trouble here.
> > 
> > Agreed.
> 
> Great.

I started to implement regmap for this driver but I run into some
problems. The registers we read/write are all 64-bit and accessed trough
readq/writeq accessors. However, the regmap API takes unsigned int:

  int regmap_write(struct regmap *map, unsigned int reg, unsigned int val);
  int regmap_read(struct regmap *map, unsigned int reg, unsigned int *val);

I'm not sure how we can take advantage of this API with the 64-bit
registers. There are "raw" versions of the functions that take void
pointer like:

 int regmap_raw_read(struct regmap *map, unsigned int reg,
                     void *val, size_t val_len);

but looking at the implementation if the register gets cached it
internally does reads in unsigned int sized chunks (if I understand it
right).

Any ideas how this can be done?

Thanks!