Messages in this thread | | | Subject | Re: [PATCH v2 2/3] spi: Add HiSilicon v3xx SPI NOR flash controller driver | From | John Garry <> | Date | Fri, 31 Jan 2020 16:26:46 +0000 |
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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
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