[U-Boot] at91 spi bus speed
Hi,
I'm experiencing some strange spi behaviour with an at91sam9g20. I changed the spi_xfer code (atmel_spi.c) to make use of the PDC that the at91sam9g20 offers. This works fine, but only up to an spi bus speed of 10 to 12 MHz. After that I see the CS going down sometimes before the transfer is complete. When the frequency is increased the issue starts appearing more often.
I saw that in env_sf.c that the spi bus speed is set at 10 MHz and was wondering if there was a specific reason for that?
10 MHz is acceptible but I would like to understand what is happening, so if anybody experienced and maybe even investigated the problem, please let me know.
Wouter Moors
On Tuesday, February 15, 2011 06:56:42 wouter moors wrote:
I saw that in env_sf.c that the spi bus speed is set at 10 MHz and was wondering if there was a specific reason for that?
you mean it defaults to 10 MHz. boards can freely pick anything they want. some speed needed to be arbitrarily picked, and 10 MHz should work with every spi flash out there. -mike
So the 10MHz is a safe value I guess. But I was wondering most why the bus speed seems to be limited to ~12MHz. Is that a limitation of the at91sam9g20 or more likely a problem with the board design?
On Tue, Feb 15, 2011 at 9:08 PM, Mike Frysinger vapier@gentoo.org wrote:
On Tuesday, February 15, 2011 06:56:42 wouter moors wrote:
I saw that in env_sf.c that the spi bus speed is set at 10 MHz and was wondering if there was a specific reason for that?
you mean it defaults to 10 MHz. boards can freely pick anything they want. some speed needed to be arbitrarily picked, and 10 MHz should work with every spi flash out there. -mike
On Wednesday, February 16, 2011 03:26:00 wouter moors wrote:
please dont top post
But I was wondering most why the bus speed seems to be limited to ~12MHz. Is that a limitation of the at91sam9g20 or more likely a problem with the board design?
i was merely covering a question on common code. ive never used u-boot on an arm part let alone the one you quote, so i dont have a clue in that regard. sorry. -mike
participants (2)
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Mike Frysinger -
wouter moors