From: Michael Walle <michael@walle.cc>
To: Tudor Ambarus <tudor.ambarus@linaro.org>
Cc: Mark Brown <broonie@kernel.org>,
tudor.ambarus@microchip.com, alexandre.belloni@bootlin.com,
claudiu.beznea@microchip.com, devicetree@vger.kernel.org,
krzysztof.kozlowski+dt@linaro.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org,
linux-spi@vger.kernel.org, nicolas.ferre@microchip.com,
robh+dt@kernel.org
Subject: Re: [PATCH 1/8] spi: dt-bindings: Introduce spi-cs-setup-ns property
Date: Mon, 02 Jan 2023 14:21:59 +0100 [thread overview]
Message-ID: <5ed88e3c3c105fdce1bb16ff16cde32f@walle.cc> (raw)
In-Reply-To: <1ee9cf77-1ca0-6e4e-ba7d-896838bd71de@linaro.org>
>>>>>> + spi-cs-setup-ns:
>>>>>> + description:
>>>>>> + Delay in nanosecods to be introduced by the controller
>>>>>> after CS is
>>>>>> + asserted.
>>>>
>>>>> Does this need a type as the spi-cs-setup-ns is apparently just
>>>>> 16bit? At
>>>>> least the driver uses it that way.
>>>>
>>>>> But IMHO this should just be a normal uint32 value to be consistent
>>>>> with
>>>>> all the other properties. Also the max value with 16bit will be
>>>>> 'just'
>>>>> 65us.
>>>>
>>>> Making it 32 bit does seem safer. I've applied the series
>>>
>>> Thanks. There are few implications to consider before making this
>>> prop a
>>> u32, and I'd like to check them with you.
>>>
>>> struct spi_delay will have to be updated to have a u32 value, now
>>> it's a
>>> u16. This means that we'll have to update spi_delay_to_ns() to either
>>> return a s64 or to add a u64 *delay parameter to the function so that
>>> we
>>> can still handle the conversions from usecs and the error codes in
>>> the
>>> SPI_DELAY_UNIT_SCK case. Then all its callers have to be updated to
>>> consider the u64 delay.
>>
>> I was talking about the device tree property. Even if the driver
>> continue
>> to use just 16bit, the DT property could be 32bit IMHO.
>
> but then you'll have an implicit cast to u16 at:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/spi/spi.c#n2314
> which will make the u32 dt prop misleading.
Nothing will prevent you from checking for a valid range and return an
error :)
But I agree, that converting the u16 to u32 in the driver is probably
the better way.
>> At the moment, the schema says its 32bit (if I'm not mistaken, because
>> it doesn't have a type), but the driver will parse the property as
>> 16bit and your device tree also has this /bits/ thingy. So regardless
>> if the driver is using 16bit or 32bit for the value, there seems to be
>> a discrepancy between the schema and the devicetree (and driver).
>
> okay, thanks for pointing it out. Let's decide how we fix this.
>
>>
>> All other properties are just the regular 32bit values, thus I was
>> suggesting to change the DT property to 32bit.
>
> If we want to change the dt prop to 32bit I think we should also handle
> the parsed value as u32, not as u16.
Strictly speaking, your device tree is wrong, because the schema
already says it's 32bit.
-michael
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next prev parent reply other threads:[~2023-01-02 13:22 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-17 10:52 [PATCH 0/8] spi: Introduce spi-cs-setup-ns dt property Tudor Ambarus
2022-11-17 10:52 ` [PATCH 1/8] spi: dt-bindings: Introduce spi-cs-setup-ns property Tudor Ambarus
2022-11-18 14:14 ` Michael Walle
2022-11-18 15:30 ` Mark Brown
2023-01-02 9:37 ` Tudor Ambarus
2023-01-02 11:48 ` Michael Walle
2023-01-02 12:11 ` Tudor Ambarus
2023-01-02 13:21 ` Michael Walle [this message]
2022-11-17 10:52 ` [PATCH 2/8] spi: " Tudor Ambarus
2022-11-17 10:52 ` [PATCH 3/8] spi: Reintroduce spi_set_cs_timing() Tudor Ambarus
2022-11-17 10:52 ` [PATCH 4/8] spi: atmel-quadspi: Add support for configuring CS timing Tudor Ambarus
2022-11-17 10:52 ` [PATCH 5/8] ARM: dts: at91-sama5d27_wlsom1: Set sst26vf064b SPI NOR flash at its maximum frequency Tudor Ambarus
2023-03-28 8:51 ` Nicolas Ferre
2023-03-28 9:36 ` Tudor Ambarus
2022-11-17 10:52 ` [PATCH 6/8] ARM: dts: at91-sama5d27_som1: " Tudor Ambarus
2022-11-17 10:52 ` [PATCH 7/8] ARM: dts: at91: sama5d2_icp: " Tudor Ambarus
2022-11-17 10:52 ` [PATCH 8/8] ARM: dts: at91: sam9x60ek: " Tudor Ambarus
2022-11-18 14:04 ` (subset) [PATCH 0/8] spi: Introduce spi-cs-setup-ns dt property Mark Brown
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