[Bug 1001078] New: STM32 flash driver support for non-aligned source buffers.

[Bug 1001078] New: STM32 flash driver support for non-aligned source buffers.

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           Summary: STM32 flash driver support for non-aligned source
                    buffers.
           Product: eCos
           Version: CVS
          Platform: stm32e_eval (ST STM3210E EVAL board)
        OS/Version: Cortex-M
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: low
         Component: Flash
        AssignedTo: unassigned@bugs.ecos.sourceware.org
        ReportedBy: chris@zynaptic.com
                CC: ecos-bugs@ecos.sourceware.org
             Class: Advice Request


Created an attachment (id=1024)
 --> (http://bugs.ecos.sourceware.org/attachment.cgi?id=1024)
Patch to support non-aligned source buffers for STM32 flash.

The current CVS version of the STM32 flash driver requires the source buffer to
be 16-bit aligned for writes.  This causes problems when attempting to program
the flash from data held in non-aligned buffers.  I am currently using the
attached patch to work around this.

In addition the patched version checks that the length of the write data is an
integer number of flash words, rather than silently discarding the last byte
when an odd number of bytes is written.

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[Bug 1001078] STM32 flash driver support for non-aligned source buffers.

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Jonathan Larmour <jifl@ecoscentric.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
                 CC|                            |jifl@ecoscentric.com
         AssignedTo|unassigned@bugs.ecos.source |jifl@ecoscentric.com
                   |ware.org                    |
     Ever Confirmed|0                           |1
               Flag|                            |Patch_or_Contribution+

--- Comment #1 from Jonathan Larmour <jifl@ecoscentric.com> 2010-11-21 21:50:05 GMT ---
I'm not keen on this patch I'm afraid. The other drivers (e.g. AM29xxxxxv2,
stratav2) have the same constraints and intentionally enforce alignment. I
don't want to go down the route of people expecting unaligned data to be ok
(and then they'd be likely to claim it is a "bug" for unaligned data not to be
accepted by any driver).

That said, I wouldn't have a problem with this being a driver-specific CDL
option if you wanted to rework it on those lines, if you're keen.

The length alignment check is reasonable in any case of course.

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[Bug 1001078] STM32 flash driver support for non-aligned source buffers.

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Jonathan Larmour <jifl@ecoscentric.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Attachment #1024|                            |assignment+, review-
               Flag|                            |

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[Bug 1001078] STM32 flash driver support for non-aligned source buffers.

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--- Comment #2 from Chris Holgate <chris@zynaptic.com> 2010-11-22 22:03:18 GMT ---
To give some context, I needed non-aligned writes for my particular application
because I was replacing an external SPI flash with an area of integrated flash,
and write data was being sourced from a non-aligned USB packet buffer.  I
suppose the acid test for whether the extra CDL option is worth including is
how many other people are likely to find themselves in a similar position.  If
the answer is 'not many', it may be better for me to just publish the
modifications in a GPL compliant manner when I finally get round to shipping my
product.

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[Bug 1001078] New: STM32 flash driver support for non-aligned source buffers.

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           Summary: STM32 flash driver support for non-aligned source
                    buffers.
           Product: eCos
           Version: CVS
          Platform: stm32e_eval (ST STM3210E EVAL board)
        OS/Version: Cortex-M
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: low
         Component: Flash
        AssignedTo: unassigned@bugs.ecos.sourceware.org
        ReportedBy: chris@zynaptic.com
                CC: ecos-bugs@ecos.sourceware.org
             Class: Advice Request


Created an attachment (id=1024)
 --> (http://bugs.ecos.sourceware.org/attachment.cgi?id=1024)
Patch to support non-aligned source buffers for STM32 flash.

The current CVS version of the STM32 flash driver requires the source buffer to
be 16-bit aligned for writes.  This causes problems when attempting to program
the flash from data held in non-aligned buffers.  I am currently using the
attached patch to work around this.

In addition the patched version checks that the length of the write data is an
integer number of flash words, rather than silently discarding the last byte
when an odd number of bytes is written.

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[Bug 1001078] STM32 flash driver support for non-aligned source buffers.

[bugzilla-daemon]

Please do not reply to this email. Use the web interface provided at:
http://bugs.ecos.sourceware.org/show_bug.cgi?id=1001078

Jonathan Larmour <jifl@ecoscentric.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
                 CC|                            |jifl@ecoscentric.com
         AssignedTo|unassigned@bugs.ecos.source |jifl@ecoscentric.com
                   |ware.org                    |
     Ever Confirmed|0                           |1
               Flag|                            |Patch_or_Contribution+

--- Comment #1 from Jonathan Larmour <jifl@ecoscentric.com> 2010-11-21 21:50:05 GMT ---
I'm not keen on this patch I'm afraid. The other drivers (e.g. AM29xxxxxv2,
stratav2) have the same constraints and intentionally enforce alignment. I
don't want to go down the route of people expecting unaligned data to be ok
(and then they'd be likely to claim it is a "bug" for unaligned data not to be
accepted by any driver).

That said, I wouldn't have a problem with this being a driver-specific CDL
option if you wanted to rework it on those lines, if you're keen.

The length alignment check is reasonable in any case of course.

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