Boris Brezillon <boris.brezillon@xxxxxxxxxxx> writes:
> On Thu, 08 Feb 2018 15:15:42 +0000
> Eric Anholt <eric@xxxxxxxxxx> wrote:
>
>> Boris Brezillon <boris.brezillon@xxxxxxxxxxx> writes:
>>
>> > In order to enable a PLL, not only the PLL has to be powered up and
>> > locked, but you also have to de-assert the reset signal. The last part
>> > was missing. Add it so PLLs that were not enabled by the FW/bootloader
>> > can be enabled from Linux.
>> >
>> > Fixes: 41691b8862e2 ("clk: bcm2835: Add support for programming the audio domain clocks")
>> > Cc: <stable@xxxxxxxxxxxxxxx>
>> > Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxx>
>> > ---
>> > drivers/clk/bcm/clk-bcm2835.c | 7 +++++++
>> > 1 file changed, 7 insertions(+)
>> >
>> > diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
>> > index a07f6451694a..6c5d4a8e426c 100644
>> > --- a/drivers/clk/bcm/clk-bcm2835.c
>> > +++ b/drivers/clk/bcm/clk-bcm2835.c
>> > @@ -602,6 +602,9 @@ static void bcm2835_pll_off(struct clk_hw *hw)
>> > const struct bcm2835_pll_data *data = pll->data;
>> >
>> > spin_lock(&cprman->regs_lock);
>> > + cprman_write(cprman, data->a2w_ctrl_reg,
>> > + cprman_read(cprman, data->a2w_ctrl_reg) &
>> > + ~A2W_PLL_CTRL_PRST_DISABLE);
>> > cprman_write(cprman, data->cm_ctrl_reg,
>> > cprman_read(cprman, data->cm_ctrl_reg) |
>> > CM_PLL_ANARST);
>>
>> For turning off, the FW just does the equivalent of:
>>
>> cprman_write(cprman, data->cm_ctrl_reg, CM_PLL_ANARST);
>> cprman_write(cprman, data->a2w_ctrl_reg, A2W_PLL_CTRL_PWRDN);
>
> Hm, the write to ->a2w_ctrl_reg overwrites the
> NDIV/PDIV values done in bcm2835_pll_set_rate(). So, either we do:
>
> cprman_write(cprman, data->cm_ctrl_reg, CM_PLL_ANARST);
> cprman_write(cprman, data->a2w_ctrl_reg,
> cprman_read(cprman, data->a2w_ctrl_reg) |
> A2W_PLL_CTRL_PWRDN);
>
> or we cache the pdiv/ndiv values in struct bcm2835_pll and only apply
> them in bcm2835_pll_on().
>
> I'd recommend going for the former to keep the changes easily
> backportable to older kernels.
Oh, right. I like your cprman_write() solution above.
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