include/drivers/flash: document on the unrestricted alignment of reads #23628

nvlsianpu · 2020-03-20T10:20:56Z

Unaligned read-out capability become fact among all drivers.
Let's cut this in stone as API requirement.

Signed-off-by: Andrzej Puzdrowski andrzej.puzdrowski@nordicsemi.no

carlescufi · 2020-03-20T12:47:29Z

include/drivers/flash.h

- *  Most of flash drivers support unaligned flash access, but some have
- *  restrictions on the read offset or/and the read size. Please refer to
- *  the driver implementation to get details on the read alignment requirement.
+ *  Each of flash drivers support unaligned flash access, without any


s/Each of/ All

include/drivers/flash.h

carlescufi · 2020-05-19T16:36:24Z

Blocked by #25292

carlescufi · 2020-05-19T16:42:24Z

API Meeting:

@nvlsianpu did you check all the current drivers beyond the qspi?
@nvlsianpu did you consider a compile-time option? I seem to recall you did, but I don't remember what the outcome of that dicussion was
During the API meeting it was suggested we could default to not supporting unaligned access unless a Kconfig option is enabled, hence the previous question

cc @pabigot @sglass68
This will be scheduled for discussion in the next API meeting.

pabigot · 2020-05-19T17:04:50Z

Blocked by #25292

I don't think that PR blocks this change, but it highlights that QSPI needs work before the new requirement can be confirmed. That is a minimal change for a very specific function to support using an external flash to store the alternative image for mcuboot (fixing #25289).

Also we should extend the AU promise to not only alignment but memory region: i.e. that it is permitted to writes of data that is located in flash, rather than RAM, which impacts any implementation (like QSPI) that uses DMA that only works on RAM addresses.

Adds the functionality of doing one byte write to QSPI nor driver. This is achived through the use of stack in the function calls. Can be removed when requirements in zephyrproject-rtos/zephyr#23628 are fulfilled in the QSPI NOR driver. NCSDK-4628 Signed-off-by: Sigvart Hovland <sigvart.m@gmail.com>

Adds the functionality of doing one byte write to QSPI nor driver. This is achived through the use of stack in the function calls. Can be removed when requirements in zephyrproject-rtos/zephyr#23628 are fulfilled in the QSPI NOR driver. NCSDK-4628 Signed-off-by: Sigvart Hovland <sigvart.m@gmail.com> (cherry picked from commit 9d4faff)

nvlsianpu · 2020-07-17T09:15:48Z

#26772 going to add unrestricted alignment of reads for nordic qspi flash driver.

pabigot

I believe the exception for QSPI has been addressed, so this can be updated and merged after other issues addressed.

We should also document the expectations regarding memory region for material written to the device. In particular that even if a device only supports DMA, and DMA requires the source buffer be in RAM, that it must still be permitted to write material where the source buffer is in flash. Or, if that is not required, document that on some devices such writes may fail and will return a particular error code.

nvlsianpu · 2020-08-03T15:03:01Z

@pabigot

We should also document the expectations regarding memory region for material written to the device. In particular that even if a device only supports DMA, and DMA requires the source buffer be in RAM, that it must still be permitted to write material where the source buffer is in flash. Or, if that is not required, document that on some devices such writes may fail and will return a particular error code.

For being consistent I prefer to force all to support source buffer anywhere.

nvlsianpu · 2020-08-05T14:55:48Z

@pabigot Added note on write source buffer location.

carlescufi · 2020-08-05T15:01:30Z

@pabigot Added note on write source buffer location.

Thanks @nvlsianpu. @pabigot please take another look.

pabigot · 2020-08-05T15:05:25Z

include/drivers/flash.h

@@ -121,6 +120,8 @@ static inline int z_impl_flash_read(struct device *dev, off_t offset, void *data
 /**
 *  @brief  Write buffer into flash memory.
 *
+ *  All flash drivers support source buffer located either in RAM or SoC flash.


For complete clarity this should include the same text on alignment and sizes that was added for read.

check once more, propose redaction as I'm not english native

How about for read:

All flash drivers support reads without alignment restrictions on the read offset, the read size, or the destination address.

and for write:

All flash drivers support a source buffer located either in RAM or SoC flash, without alignment restrictions on the source address, or write size or offset.

?

Unaligned read-out capability become fact among all drivers. Let's cut this in stone as API requirement. fixes zephyrproject-rtos#16439 Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>

Document unrestricted source buffer location while writing to the flash. Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>

…ites Telling that all the driver supports unaligned writes was and is not true. Drivers only have to support any source buffer. This fix message introduced by zephyrproject-rtos#23628 Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>

…ites Telling that all the driver supports unaligned writes was and is not true. Drivers only have to support any source buffer. This fix message introduced by #23628 Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>

nvlsianpu added area: Documentation area: API Changes to public APIs labels Mar 20, 2020

nvlsianpu requested review from nashif, superna9999, pabigot, vanwinkeljan, MaureenHelm, aurel32, carlescufi, galak, erwango, mnkp and kamlaz March 20, 2020 10:20

nvlsianpu requested a review from anangl March 20, 2020 10:31

carlescufi requested changes Mar 20, 2020

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nvlsianpu force-pushed the doc/flash-driver-read-unalined branch from 6ee8bf3 to 90fafe7 Compare March 20, 2020 13:01

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include/drivers/flash.h Outdated Show resolved Hide resolved

carlescufi approved these changes Mar 23, 2020

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pabigot mentioned this pull request May 19, 2020

drivers: flash: nrf_qspi_nor: support read of sub-word lengths #25292

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carlescufi requested a review from d3zd3z May 19, 2020 17:32

sigvartmh mentioned this pull request May 20, 2020

drivers: flash: Add one byte read write emulation to qspi nor nrf nrfconnect/sdk-zephyr#305

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nvlsianpu mentioned this pull request Jul 3, 2020

LPC legacy IAP flash driver #26609

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anangl approved these changes Jul 28, 2020

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nvlsianpu force-pushed the doc/flash-driver-read-unalined branch from 90fafe7 to 1523997 Compare August 5, 2020 14:54

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nvlsianpu force-pushed the doc/flash-driver-read-unalined branch from 1523997 to 84535a4 Compare August 5, 2020 15:10

nvlsianpu added 2 commits August 5, 2020 17:55

include/drivers/flash: document on the unrestricted alignment of reads

5d6d857

Unaligned read-out capability become fact among all drivers. Let's cut this in stone as API requirement. fixes zephyrproject-rtos#16439 Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>

include/drivers/flash: document on the unrestricted source buffers

4b099e6

Document unrestricted source buffer location while writing to the flash. Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>

nvlsianpu force-pushed the doc/flash-driver-read-unalined branch from 84535a4 to 4b099e6 Compare August 5, 2020 15:56

pabigot approved these changes Aug 5, 2020

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nashif merged commit 4d4455b into zephyrproject-rtos:master Aug 5, 2020

This was referenced Sep 8, 2020

include/drivers/flash: correction on the unrestricted alignment of writes #28192

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include/drivers/flash: API stands mistakenly unrestricted alignment of writes. #28193

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pabigot mentioned this pull request Sep 9, 2020

flash: revise API to remove block restrictions on write operations #28220

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include/drivers/flash: document on the unrestricted alignment of reads #23628

include/drivers/flash: document on the unrestricted alignment of reads #23628

nvlsianpu commented Mar 20, 2020

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include/drivers/flash: document on the unrestricted alignment of reads #23628

include/drivers/flash: document on the unrestricted alignment of reads #23628

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