lkml.org 
[lkml]   [2020]   [Jan]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v2 2/3] spi: Add HiSilicon v3xx SPI NOR flash controller driver
From
Date
On 31/01/2020 15:46, Andy Shevchenko wrote:
> On Fri, Jan 31, 2020 at 2:03 PM John Garry <john.garry@huawei.com> wrote:
>> On 31/01/2020 11:39, Andy Shevchenko wrote:
>>> On Fri, Jan 31, 2020 at 12:08 PM John Garry <john.garry@huawei.com> wrote:
>>>> On 13/01/2020 14:34, Andy Shevchenko wrote:
>
> ...
>
>>>> About this topic of ACPI having no method to describe device buswidth in
>>>> the resource descriptor, it may be an idea for me to raise a Tianocore
>>>> feature request @ https://bugzilla.tianocore.org/
>>>>
>>>
>>> The 19.6.126 describes the SPI resource, in particular:
>>>
>>> ---8<---8<---
>>> DataBitLength is the size, in bits, of the smallest transfer unit for
>>> this connection. _LEN is automatically
>>> created to refer to this portion of the resource descriptor.
>>> ---8<---8<---
>>>

Hi Andy,

>>> Is it what you are looking for? (As far as I know most of the
>>> firmwares simple abuse this field among others)
>>
>> I didn't think so - I thought that there was a distinction between width
>> and length in SPI terms.
>
> My interpretation of this field is a data width of the slave.
> Basically what we have as transfer->size inside SPI in the Linux
> kernel.
>
>> So how do you find that most firmwares abuse this field? AFAICS, linux
>> kernel doesn't interpret this field at all.
>
>>From all tables I have this is the result of appearance (some of the
> tables are like 10x times present in my data base, but nevertheless)
>
> 140 SpiSerialBusV2(0x0000,PolarityHigh,FourWireMode,0x08,
> 411 SpiSerialBusV2(0x0000,PolarityLow,FourWireMode,0x08,
> 1 SpiSerialBusV2(0x0000,PolarityLow,FourWireMode,0x08,
> 36 SpiSerialBusV2(0x0000,PolarityLow,FourWireMode,0x10,
> 35 SpiSerialBusV2(0x0000,PolarityLow,FourWireMode,0x18,
> 35 SpiSerialBusV2(0x0000,PolarityLow,FourWireMode,0x20,
> 1 SpiSerialBusV2(0x0000,PolarityLow,ThreeWireMode,0x10,
> 8 SpiSerialBusV2(0x0001,PolarityLow,FourWireMode,0x08,
> 1 SpiSerialBusV2(0x0001,PolarityLow,FourWireMode,0x10,
>
> So, it seems I stand corrected, the field is in right use, although
> cases like 0x10 and 0x20 should be carefully checked.
>
> We may teach kernel to get something meaningful out of it.
>

It seems that someone already had a go at that:
https://lore.kernel.org/lkml/20170317212143.bogj6efzyvvf24yd@sirena.org.uk/

Thanks,
John

\
 
 \ /
  Last update: 2020-01-31 17:27    [W:0.073 / U:0.032 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site