[PATCH v2 01/13] mfd: pruss mfd driver.

[Subhasish Ghosh]

I am not sure if I understood you correctly, but the current sizeof the 
structure da8xx_prusscore_regs  is 0x500.

Here is a link to the PRUSS memory map:
http://processors.wiki.ti.com/index.php/PRUSS_Memory_Map

The offset 0x00007000 is the PRU0 reg offset and 0x00007800 is the PRU1 reg 
offset.
We cannot have a register file larger than this, but lot of space is left 
out, possibly for future development.

--------------------------------------------------
From: "Samuel Ortiz" <sameo at linux.intel.com>
Sent: Tuesday, February 22, 2011 5:03 PM
To: "Wolfgang Grandegger" <wg at grandegger.com>
Cc: "Subhasish Ghosh" <subhasish at mistralsolutions.com>; 
<sachi at mistralsolutions.com>; 
<davinci-linux-open-source at linux.davincidsp.com>; <nsekhar at ti.com>; "open 
list" <linux-kernel at vger.kernel.org>; <m-watkins at ti.com>; 
<linux-arm-kernel at lists.infradead.org>
Subject: Re: [PATCH v2 01/13] mfd: pruss mfd driver.

> On Tue, Feb 22, 2011 at 11:48:51AM +0100, Wolfgang Grandegger wrote:
>> On 02/22/2011 11:31 AM, Samuel Ortiz wrote:
>> > Hi Subhasish,
>> >
>> > On Tue, Feb 22, 2011 at 11:13:38AM +0530, Subhasish Ghosh wrote:
>> >> Thank you for your comments.
>> > No problem.
>> >
>> >>>> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
>> >>>> index fd01836..6c437df 100644
>> >>>> --- a/drivers/mfd/Kconfig
>> >>>> +++ b/drivers/mfd/Kconfig
>> >>>> @@ -81,6 +81,16 @@ config MFD_DM355EVM_MSP
>> >>>>   boards.  MSP430 firmware manages resets and power sequencing,
>> >>>>   inputs from buttons and the IR remote, LEDs, an RTC, and more.
>> >>>>
>> >>>> +config MFD_DA8XX_PRUSS
>> >>>> + tristate "Texas Instruments DA8XX PRUSS support"
>> >>>> + depends on ARCH_DAVINCI && ARCH_DAVINCI_DA850
>> >>> Why are we depending on those ?
>> >>
>> >> SG -- The PRUSS core in only available within DA850 and DA830,
>> >>            DA830 support is not yet implemented.
>> > Sure, but if there are no actual code dependencies, I'd like to get rid 
>> > of
>> > those depends.
>> >
>> >>>> +u32 pruss_disable(struct device *dev, u8 pruss_num)
>> >>>> +{
>> >>>> + struct da8xx_pruss *pruss = dev_get_drvdata(dev->parent);
>> >>>> + da8xx_prusscore_regs h_pruss;
>> >>>> + u32 temp_reg;
>> >>>> +
>> >>>> + if (pruss_num == DA8XX_PRUCORE_0) {
>> >>>> + /* Disable PRU0  */
>> >>>> + h_pruss = (da8xx_prusscore_regs)
>> >>>> + ((u32) pruss->ioaddr + 0x7000);
>> >>> So it seems you're doing this in several places, and I have a few
>> >>> comments:
>> >>>
>> >>> - You don't need the da8xx_prusscore_regs at all.
>> >>> - Define the register map through a set of #define in your header 
>> >>> file.
>> >>> - Use a static routine that takes the core number and returns the
>> >>> register map
>> >>> offset.
>> >>>
>> >>> Then routines like this one will look a lot more readable.
>> >>
>> >> SG -- There are a huge number of PRUSS registers. A lot of them are
>> >> reserved and are expected to change as development on the
>> >>            controller is still ongoing.
>> > First of all, from what I read in your patch you're only using the 
>> > CONTROL
>> > offset.
>> >
>> >> If we use #defines to plot
>> >> all the registers, then first, there are too many array type
>> >> registers which will need to be duplicated.
>> > What I'm expecting is a small set of defines for the register offsets. 
>> > You
>> > have 13 fields in your da8xx_prusscore_regs, you only need to define 13
>> > register offsets.
>> >
>> > So, if you have a:
>> >
>> > static u32 reg_offset(struct device *dev, u8 pru_num)
>> > {
>> > struct da8xx_pruss *pru = dev_get_drvdata(dev->parent);
>> >
>> > switch (pru_num) {
>> > case DA8XX_PRUCORE_0:
>> > return (u32) pru->ioaddr + 0x7000;
>> > case DA8XX_PRUCORE_1:
>> > return (u32) pru->ioaddr + 0x7800;
>> > default:
>> > return 0;
>> > }
>> >
>> >
>> > then routines like pruss_enable (which should return an int, btw) would 
>> > look
>> > like:
>> >
>> > int pruss_enable(struct device *dev, u8 pruss_num)
>> > {
>> > u32 offset = reg_offset(dev, pruss_num);
>> >
>> > if (offset == 0)
>> > return -EINVAL;
>> >
>> > __raw_writel(DA8XX_PRUCORE_CONTROL_RESETVAL,
>> > offset + PRU_CORE_CONTROL);
>> >
>> > return 0;
>> > }
>>
>> All registers are memory mapped and could nicely be described by
>> structures (and sub-structures). Therefore we asked to considerer
>> structs, at least for the Pruss SocketCAN drivers.
>>
>> That would result in
>> much much clearer and better readable code. The code above would shrink 
>> to:
>>
>> __raw_writel(DA8XX_PRUCORE_CONTROL_RESETVAL,
>>      &prucore[pruss_num].control);
> This driver seems to exclusively use the control offset, which is why I 
> don't
> see an absolute need for doing this mapping.
> But if both maps are contiguous then doing the mapping would prevent us 
> from
> calling reg_offset() and would bring some advantage. I'd then be fine with 
> it.
> For now, da8xx_prusscore_regs seems to be larger than the 0x800 interval
> between the 2 maps, so I have no idea if both maps are indeed contiguous.
>
> Cheers,
> Samuel.
>
> -- 
> Intel Open Source Technology Centre
> http://oss.intel.com/