On 03/15/2018 07:34 AM, Sekhar Nori wrote:
Hi David,
On Thursday 15 March 2018 07:06 AM, David Lechner wrote:
commit 1601dd97edc6 ("davinci: omapl138_lcdk: increase PLL0 frequency")
changed the PLL0 frequency to 456MHz, which is needed for the LCDC IP
block. However, in doing so, it caused the PLLOUT clock to be outside
of the allowable specifications given in the OMAP-L138 data sheet. (It
says PLLOUT must be 600MHz max). It also uses a PLLM value outside of
the range given in the TRM (it says PLLM must in the range 0 to 0x1f).
So here is what we have currently:
PLLOUT = 24 / (0 + 1) * (37 + 1) = 912MHz (out of spec)
^ ^ ^
CLKIN PREDIV PLLM (out of spec)
input to PLLDIVn = 912 / (1 + 1) = 456MHz (desired result)
^ ^
PLLOUT POSTDIV
This changes the PLLM value to 18 and the POSTDIV value to 0 so that
PLLOUT is now within specification but we still get the desired
result.
PLLOUT = 24 / (0 + 1) * (18 + 1) = 456MHz (within spec)
^ ^ ^
CLKIN PREDIV PLLM
input to PLLDIVn = 456 / (0 + 1) = 456MHz (desired result)
^ ^
PLLOUT POSTDIV
Fixes: 1601dd97edc6 ("davinci: omapl138_lcdk: increase PLL0 frequency")
Signed-off-by: David Lechner <da...@lechnology.com>
Thanks for the patch and great description. It looks correct to me.
Hopefully I can provide some testing feedback too soon.
---
FYI, I haven't been able to test this patch yet. The changes affect the SPL
image, which has to be flashed to SPI. I am having trouble with the flash
utility[1] running on Linux. It gets stuck at:
0% [ ------------------------------------------------------------ ]
Programming application into flash...
So, if anyone has some advice on how to make it work or can test the patch,
that would be helpful.
The easiest thing to do would be to shift to MMC/SD boot so you can
easily update images.
Before starting though, I would take note of out-of-the-box boot switch
settings and also take a disk image backup of the SD card. Or better
yet, just use another SD card.
Setup the SW1 dip switch thus:
http://processors.wiki.ti.com/index.php/How_to_boot_OMAP-L138_LCDK_from_SD_card#Settings_DIP_switches_to_SD.2FMMC_boot_mode
Prepare an SD card for boot:
$ sudo dd if=u-boot.ais of=/dev/sd<N> seek=117 bs=512 conv=fsync
Thanks for the tips. I've actually done exactly that (using my own SD card).
However, these changes affect the u-boot SPL image only. I was able to put
the regular u-boot.ais on the SD card, but I'm having troubling figuring
out how to install the SPL image.
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