From: David Laight <David.Laight@ACULAB.COM>
To: 'Eddie James' <email@example.com>,
Cc: "firstname.lastname@example.org" <email@example.com>,
Subject: RE: [PATCH 0/2] spi: fsi: Reduce max transfer size to 8 bytes
Date: Sat, 17 Jul 2021 13:46:15 +0000 [thread overview]
Message-ID: <0ed7c393b7aa4252a48cd2397ac251eb@AcuMS.aculab.com> (raw)
From: Eddie James
> Sent: 16 July 2021 14:39
> The security restrictions on the FSI-attached SPI controllers have
> been applied universally to all controllers, so the controller can no
> longer transfer more than 8 bytes for one transfer. Refactor the driver
> to remove the looping and support for larger transfers, and remove the
> "restricted" compatible string, as all the controllers are now
> considered restricted.
Aren't there significant performance (and device wear?) penalties
for doing short SPI eeprom writes?
IIRC (and I'm not getting my serial busses confused) a write request
can request an aligned transfer of up to (typically) 32 bytes.
At which point you need to wait for the status to indicate 'complete'.
So restricting writes to 8 bytes increases block write times
by a factor of 4.
Increasing the numbers of writes by a factor or 4 may also have
an effect on device wear - but that is more likely only affected
by erase cycles.
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next prev parent reply other threads:[~2021-07-17 13:53 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-16 13:39 [PATCH 0/2] spi: fsi: Reduce max transfer size to 8 bytes Eddie James
2021-07-16 13:39 ` [PATCH 1/2] " Eddie James
2021-07-16 17:19 ` Mark Brown
2021-07-16 18:34 ` Eddie James
2021-07-19 15:20 ` Mark Brown
2021-07-19 15:46 ` Eddie James
2021-07-20 13:04 ` David Laight
2021-07-20 13:13 ` Mark Brown
2021-07-20 17:32 ` David Laight
2021-07-16 13:39 ` [PATCH 2/2] dt-bindings: fsi: Remove ibm, fsi2spi-restricted compatible Eddie James
2021-07-19 15:54 ` [PATCH 2/2] dt-bindings: fsi: Remove ibm,fsi2spi-restricted compatible Mark Brown
2021-07-17 13:46 ` David Laight [this message]
2021-07-19 15:57 ` [PATCH 0/2] spi: fsi: Reduce max transfer size to 8 bytes Eddie James
2021-07-19 18:00 ` Mark Brown
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