[U-Boot] [PATCH 4/7] ARM: sun6i: Add clock support

[Hans de Goede]

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 :)

Regards,

Hans