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* [PATCH v3 0/2] tpm_tis_spi: Use DMA-safe memory
@ 2017-08-24  8:27 Alexander Steffen
       [not found] ` <20170824082745.9372-1-Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/>
  0 siblings, 1 reply; 10+ messages in thread
From: Alexander Steffen @ 2017-08-24  8:27 UTC (permalink / raw)
  To: jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA,

The documentation says that DMA-safe memory is required for SPI transfers.
The I/O buffers passed in by the caller can be allocated anywhere,
including on the stack, which is not DMA-safe. So the data needs to be
copied to separate, DMA-safe buffers.

We did not see any DMA-related issues on our test systems, even without
DMA-safe buffers. But this might simply be due to the fact that the SPI
transfer size is rather small, so our systems do not bother to set up DMA
transfers. Other systems might do so.

- Updated commit message with more explanations.

- Split into two patches, one for making the buffers DMA-safe and another
  for using only a single buffer.

Alexander Steffen (2):
  tpm_tis_spi: Use DMA-safe memory for SPI transfers
  tpm_tis_spi: Use a single buffer for SPI transfers

 drivers/char/tpm/tpm_tis_spi.c | 32 ++++++++++++++++++--------------
 1 file changed, 18 insertions(+), 14 deletions(-)


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^ permalink raw reply	[flat|nested] 10+ messages in thread

end of thread, other threads:[~2017-08-31 12:34 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-08-24  8:27 [PATCH v3 0/2] tpm_tis_spi: Use DMA-safe memory Alexander Steffen
     [not found] ` <20170824082745.9372-1-Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/>
2017-08-24  8:27   ` [PATCH v3 1/2] tpm_tis_spi: Use DMA-safe memory for SPI transfers Alexander Steffen
2017-08-25 16:39     ` Jarkko Sakkinen
2017-08-24  8:27   ` [PATCH v3 2/2] tpm_tis_spi: Use a single buffer " Alexander Steffen
     [not found]     ` <20170824082745.9372-3-Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/>
2017-08-25 16:39       ` Jarkko Sakkinen
2017-08-26 11:22   ` [PATCH v3 0/2] tpm_tis_spi: Use DMA-safe memory Jarkko Sakkinen
     [not found]     ` <20170826112259.ypwtqbwakyfdqkzo-VuQAYsv1563Yd54FQh9/>
2017-08-29 12:14       ` Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/w
     [not found]         ` <9aea582eccbe4655b5de487dacf7c745-nFblLGNE8XKJSz+rYg/>
2017-08-30  8:42           ` Benoit HOUYERE
     [not found]             ` <>
2017-08-31 12:34               ` Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/w
2017-08-30 10:08           ` Jarkko Sakkinen

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