Re: [PATCH 12/12] clk: qcom: gcc-mdm9607: Drop redundant register update during probe

[Stephan Gerhold <stephan.gerhold@linaro.org>]

On Wed, Jun 10, 2026 at 11:01:34PM +0530, Taniya Das wrote:
> On 6/9/2026 7:44 PM, Stephan Gerhold wrote:
> > From: Stephan Gerhold <stephan@gerhold.net>
> > 
> > GPLL0 is pretty much guaranteed to be already on (and voted) during boot,
> > since it's used by the CPU and also various other components such as UART.
> > We also vote for this bit in the actual GPLL0 definition, which will be set
> > as soon as any driver in the kernel requires using the GPLL0 clock.
> > 
> > All in all, this makes separately voting for GPLL0 during probe redundant,
> > especially because the "acpuclock" in the comment is a downstream construct
> > that does not exist in upstream.
> > 
> > Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
> > ---
> >  drivers/clk/qcom/gcc-mdm9607.c | 11 +----------
> >  1 file changed, 1 insertion(+), 10 deletions(-)
> > 
> > diff --git a/drivers/clk/qcom/gcc-mdm9607.c b/drivers/clk/qcom/gcc-mdm9607.c
> > index 0bd4c12483cd..ce78ebc8ffec 100644
> > --- a/drivers/clk/qcom/gcc-mdm9607.c
> > +++ b/drivers/clk/qcom/gcc-mdm9607.c
> > @@ -1565,16 +1565,7 @@ MODULE_DEVICE_TABLE(of, gcc_mdm9607_match_table);
> >  
> >  static int gcc_mdm9607_probe(struct platform_device *pdev)
> >  {
> > -	struct regmap *regmap;
> > -
> > -	regmap = qcom_cc_map(pdev, &gcc_mdm9607_desc);
> > -	if (IS_ERR(regmap))
> > -		return PTR_ERR(regmap);
> > -
> > -	/* Vote for GPLL0 to turn on. Needed by acpuclock. */
> > -	regmap_update_bits(regmap, 0x45000, BIT(0), BIT(0));
> 
> This was to ensure that the (APCS_GPLL_ENA_VOTE) vote indeed has a vote
> from CPU. AFAIR, the boot up was not using this particular PLL vote
> register and no piggy backing for the GPLL vote.
> 

Hm, I'm not sure when this would be the case. The original LK bootloader
source code also sets this bit when enabling GPLL-related clocks, so I'm
not sure when/why this bit would be missing.

Either way, I don't think it will make a difference in practice, since
it's pretty much guaranteed that one of the later clock enable sequences
(UART, USB, ...) is going to vote for GPLL0 as well.

Thanks,
Stephan