Date:   Thu, 14 Sep 2017 10:11:46 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Baolin Wang <baolin.wang@...eadtrum.com>,
        Mark Brown <broonie@...nel.org>,
        Mark Rutland <mark.rutland@....com>, linux-spi@...r.kernel.org,
        devicetree@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] dt-bindings: spi: Add Spreadtrum ADI controller documentation

Hi Rob,

On 14 September 2017 at 03:51, Rob Herring <robh@...nel.org> wrote:
> On Fri, Sep 08, 2017 at 04:33:41PM +0800, Baolin Wang wrote:
>> This patch adds the binding documentation for Spreadtrum ADI
>> controller device.
>>
>> Signed-off-by: Baolin Wang <baolin.wang@...eadtrum.com>
>> ---
>> Changes since v1:
>>  - Add more documentation the 'sprd,hw-channels' property and why need
>>  one hardware spinlock.
>> ---
>>  .../devicetree/bindings/spi/spi-sprd-adi.txt       |   58 ++++++++++++++++++++
>>  1 file changed, 58 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/spi/spi-sprd-adi.txt
>>
>> diff --git a/Documentation/devicetree/bindings/spi/spi-sprd-adi.txt b/Documentation/devicetree/bindings/spi/spi-sprd-adi.txt
>> new file mode 100644
>> index 0000000..0f76336
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/spi/spi-sprd-adi.txt
>> @@ -0,0 +1,58 @@
>> +Spreadtrum ADI controller based on SPI framework
>
> "SPI framework" is not relevant to bindings.

OK, I will remove this in next version.

>
>> +
>> +ADI is the abbreviation of Anolog-Digital interface, which is used to access
>> +analog chip (such as PMIC) from digital chip. ADI controller follows the SPI
>> +framework for its hardware implementation is alike to SPI bus and its timing
>> +is compatile to SPI timing.
>> +
>> +ADI controller has 50 channels including 2 software read/write channels and
>> +48 hardware channels to access analog chip. For 2 software read/write channels,
>> +users should set ADI registers to access analog chip. For hardware channels,
>> +we can configure them to allow other hardware components to use it independently,
>> +which means we can just link one analog chip address to one hardware channel,
>> +then users can access the mapped analog chip address by this hardware channel
>> +triggered by hardware components instead of ADI software channels.
>> +
>> +Thus we introduce one property named "sprd,hw-channels" to configure hardware
>> +channels, the first value specifies the hardware channel id which is used to
>> +transfer data triggered by hardware automatically, and the second value specifies
>> +the analog chip address where user want to access by hardware components.
>> +
>> +Another hand since we have multi-subsystems will use unique ADI to access analog
>
> Drop "Another hand"

OK.

>
>> +chip, when one system is reading/writing data by ADI software channels, that
>> +should be under one hardware spinlock protection to prevent other systems from
>> +reading/writing data by ADI software channels at the same time, or two parallel
>> +routine of setting ADI registers will make ADI controller registers chaos to
>> +lead incorrect results. Then we need one hardware spinlock to synchronize between
>> +the multiple subsystems.
>> +
>> +Required properties:
>> +- compatible: Should be "sprd,sc9860-adi".
>> +- reg: Offset and length of ADI-SPI controller register space.
>> +- hwlocks: Reference to a phandle of a hwlock provider node.
>> +- hwlock-names: Reference to hwlock name strings defined in the same order
>> +     as the hwlocks, should be "adi".
>> +- #address-cells: Number of cells required to define a chip select address
>> +     on the ADI-SPI bus. Should be set to 1.
>> +- #size-cells: Size of cells required to define a chip select address size
>> +     on the ADI-SPI bus. Should be set to 0.
>> +
>> +Optional properties:
>> +- sprd,hw-channels: The first value specifies the hardware channel id which
>> +     is used to transfer data triggered by hardware automatically, and
>> +     the second value specifies the analog chip address where user want
>> +     to access by hardware components.
>
> Need to say this is an array of values up to ? channels.

OK. Will add in next version.

>
> I wonder if this should be a slave property. Is there a relationship

It is not a slave property, it is used to configure ADI controller to
support to access analog chip by hardware automatically.

> between the SPI address (i.e. chip select) and the "analog chip

I think they are not related. The "analog chip address" is like the
offset address of one SPI slave (analog chip can be recognized as one
SPI slave).

> address"? It sounds like the h/w channels are a protocol specific to a
> particular PMIC/MFD that this controller supports.

Yes. Very appreciated for your comments.

-- 
Baolin.wang
Best Regards

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