Re: [virtio-dev][PATCH V9 2/2] virtio-spi: add the device specification

Hi Cornelia,

On 12/21/2023 4:44 PM, Cornelia Huck wrote:
> On Thu, Dec 21 2023, Haixu Cui <[email protected]> wrote:
> 
>> Hi Cornelia,
>>       Much appreciated for your comments and please refer to my response.
>>
>> On 12/18/2023 7:04 PM, Cornelia Huck wrote:
>>> On Tue, Dec 12 2023, Haixu Cui <[email protected]> wrote:
>>>
>>> [BTW: A changelog would be useful, either in the patch or in the cover
>>> letter.]
>>
>> Sure, I summarize the major changes between these versions and will add
>> in next patch:
>>
>> changelog:
>> v8->v9:
>> - add explanation of bits_per_word_mask in config space
>> v7->v8:
>> - change device to host
>> v6->v7:
>> - fix the format problem, syntax problem
>> v5->v6:
>> - use driver/device instead guest/host
>> - add the definition of some terminologies
>> - use controller instead of master throughout the spec
>> - add buffer length validation for full-duplex transfer
>> v4->v5:
>> - use controller instead of master
>> - fix indentation issue
>> - extend the config space to expose the backend supported features
>> - add another result value to indicate parameter error
>> - add device and driver requirement about parameter checkig
>> v3->v4:
>> - fix the spell error
>> - bus_num is not SOC-specific, remove it
>> - add driver requirement to deal with the situation that the cs delay
>> parameters are not 0 but the backend doesn't support cs timing setting
>> v2->v3
>> - remove unnecessary statements and driver implimentation details
>> - add the parameters about cs timing delay and transfer delay
>> - use "le32" instead of "u32"
>> - swap the rx_buf and tx_buf in the request format
>> - add the parameters about transfer bit width
>> v1->v2:
>> - explain SPI when it is firstly used
>> - update the ambiguous expression of virtqueue
>> v0->v1:
>> - add definition of abbreviation SPI
>> - remove the ID
> 
> Thanks. Might be best to add this in the cover letter.
> 

In next patch I will add it in cover letter.

>> ---
>>
>>>
>>>> The Virtio SPI (Serial Peripheral Interface) device is a virtual
>>>> SPI controller that allows the driver to operate and use the SPI
>>>> controller under the control of the host.
>>>>
>>>> This patch adds the specification for virtio-spi.
>>>>
>>>> Signed-off-by: Haixu Cui <[email protected]>
>>>> Reviewed-by: Viresh Kumar <[email protected]>
>>>> ---
>>>>    device-types/spi/description.tex        | 281 ++++++++++++++++++++++++
>>>>    device-types/spi/device-conformance.tex |   7 +
>>>>    device-types/spi/driver-conformance.tex |   7 +
>>>>    3 files changed, 295 insertions(+)
>>>>    create mode 100644 device-types/spi/description.tex
>>>>    create mode 100644 device-types/spi/device-conformance.tex
>>>>    create mode 100644 device-types/spi/driver-conformance.tex
>>>>
>>>> diff --git a/device-types/spi/description.tex b/device-types/spi/description.tex
>>>
>>> Please move inclusion of this new file into content.tex here, instead of
>>> including a not-yet-existing file in the previous patch.
>>>
>>> (...)
>>
>>
>> Sorry, I don't quite understand here. Maybe I should not add the
>> following line in content.tex, is that so?
>>
>> \input{device-types/spi/description.tex}
> 
> No, please add this line; but do so in this patch instead of the
> previous one that only changes the wording.

I am not clear where to put this line? In the commit message or in the 
main text, e.g. at the start of the description.tex? As follows:

diff --git a/device-types/spi/description.tex 
b/device-types/spi/description.tex
new file mode 100644
index 0000000..b76258c
--- /dev/null
+++ b/device-types/spi/description.tex
@@ -0,0 +1,281 @@
+\input{device-types/spi/description.tex}
+\section{SPI Controller Device}\label{sec:Device Types / SPI Controller 
Device}
+
...

> 
>>
>>>
>>>> +\field{mode_func_supported} indicates whether the following features are supported or not:
>>>> +        bit 0-1: CPHA feature,
>>>> +            0b00: invalid, must support as least one CPHA setting.
>>>> +            0b01: supports CPHA=0 only;
>>>> +            0b10: supports CPHA=1 only;
>>>> +            0b11: supports CPHA=0 and CPHA=1;
>>>> +
>>>> +        bit 2-3: CPOL feature,
>>>> +            0b00: invalid, must support as least one CPOL setting.
>>>> +            0b01: supports CPOL=0 only;
>>>> +            0b10: supports CPOL=1 only;
>>>> +            0b11: supports CPOL=0 and CPOL=1;
>>>> +
>>>> +        bit 4: chipselect active high feature, 0 for unsupported and 1 for supported,
>>>> +            chipselect active low must always be supported.
>>>> +
>>>> +        bit 5: LSB first feature, 0 for unsupported and 1 for supported, MSB first must always be
>>>> +            supported.
>>>> +
>>>> +        bit 6: loopback mode feature, 0 for unsupported and 1 for supported, normal mode
>>>> +            must always be supported.
>>>> +
>>>> +Note: CPOL is clock polarity and CPHA is clock phase. If CPOL is 0, the clock idles at the logical
>>>> +low voltage, otherwise it idles at the logical high voltage. CPHA determines how data is outputted
>>>> +and sampled.
>>>
>>> Shouldn't you also specify what CPHA==0 and CPHA==1 mean?
>>>
>>
>> Yes, I will add the following explanation:
>>
>> If CPHA is 0, the first bit is outputted immediately when chipselect is
>> active and subsequent bits are outputted on the clock edges when clock
> 
> s/when clock/when the clock/
> 
>> transitions from active level to idle level. Data is sampled on the
>> clock edges when clock transitions from idle level to active level.
> 
> same
> 
>>
>> If CPHA is 1, the first bit is outputted on the fist clock edge after
>> chipselect is active, subsequent bits are outputted on the clock edges
>> when clock transitions from idle level to active level. Data is sampled
> 
> same
> 
>> on the clock edges when clock transitions from active level to idle level.
> 
> same
> 
Ok, will update.

Thank you so much.

Thanks
Haixu Cui

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