On 28-09-14 17:42, Hans de Goede wrote:
Hi,
On 09/28/2014 05:37 PM, Ian Campbell wrote:
On Sun, 2014-09-28 at 17:23 +0200, Hans de Goede wrote:
If you take a closer look at the code you will see not all 3 writes are the
same:
/* Set PLL ldo voltage without this PLL6 does not work properly */
writel(PRCM_PLL_CTRL_LDO_DIGITAL_EN | PRCM_PLL_CTRL_LDO_ANALOG_EN |
PRCM_PLL_CTRL_EXT_OSC_EN | PRCM_PLL_CTRL_LDO_OUT_L(1140) |
PRCM_PLL_CTRL_LDO_KEY, &prcm->pll_ctrl1);
writel(PRCM_PLL_CTRL_LDO_DIGITAL_EN | PRCM_PLL_CTRL_LDO_ANALOG_EN |
PRCM_PLL_CTRL_EXT_OSC_EN | PRCM_PLL_CTRL_LDO_OUT_L(1140) |
PRCM_PLL_CTRL_LDO_KEY, &prcm->pll_ctrl1);
writel(PRCM_PLL_CTRL_LDO_DIGITAL_EN | PRCM_PLL_CTRL_LDO_ANALOG_EN |
PRCM_PLL_CTRL_EXT_OSC_EN | PRCM_PLL_CTRL_LDO_OUT_L(1140),
&prcm->pll_ctrl1);
This register is locked with a so called "key", the first write is to set
the key (and has everything else the same in case the key is already
written). The second write actually makes the changes, and the third write
clears the key bits.
Even after staring really hard I still don't see what differs in the
first and second ones ;-)
Right, that is because there is no change between the first 2, I guess
using setclr_bits to first only set the key, then only the bits, then
only clear the key would be a good idea here :)
I think I wrote those lines ages ago, and I think i used writel instead
of setclr_bits and friends initially, was to first 'copy' over the
original implementation and swap magic values for defines. Once that
could be verified to working, change over to prettier code :)
Granted, Since we have little docs and no comments, merging the first
two lines requires some testing, which without hardware is near
impossible. It would have probably worked having only set the key on the
first line, key + values on the second and leave 3rd as is.
Olliver
Regards,
Hans
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