Re: [PATCH v11 1/5] clk: qcom: regmap: add PHY clock source implementation

Bjorn Andersson
2022-06-27T20:02:25Z

On Wed 08 Jun 14:22 CDT 2022, Bjorn Helgaas wrote:

> On Wed, Jun 08, 2022 at 01:52:34PM +0300, Dmitry Baryshkov wrote:
> > On recent Qualcomm platforms the QMP PIPE clocks feed into a set of
> > muxes which must be parked to the "safe" source (bi_tcxo) when
> > corresponding GDSC is turned off and on again. Currently this is
> > handcoded in the PCIe driver by reparenting the gcc_pipe_N_clk_src
> > clock. However the same code sequence should be applied in the
> > pcie-qcom endpoint, USB3 and UFS drivers.
> >
> > Rather than copying this sequence over and over again, follow the
> > example of clk_rcg2_shared_ops and implement this parking in the
> > enable() and disable() clock operations. Supplement the regmap-mux with
> > the new clk_regmap_phy_mux type, which implements such multiplexers
> > as a simple gate clocks.
> >
> > This is possible since each of these multiplexers has just two clock
> > sources: one coming from the PHY and a reference (XO) one. If the clock
> > is running off the from-PHY source, report it as enabled. Report it as
> > disabled otherwise (if it uses reference source).
> >
> > This way the PHY will disable the pipe clock before turning off the
> > GDSC, which in turn would lead to disabling corresponding pipe_clk_src
> > (and thus it being parked to a safe, reference clock source). And vice
> > versa, after enabling the GDSC the PHY will enable the pipe clock, which
> > would cause pipe_clk_src to be switched from a safe source to the
> > working one.
> >
> > Reviewed-by: Johan Hovold <johan+linaro@kernel.org>
> > Tested-by: Johan Hovold <johan+linaro@kernel.org>
> > Reported-by: kernel test robot <lkp@intel.com>
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> > ---
> > drivers/clk/qcom/Makefile | 1 +
> > drivers/clk/qcom/clk-regmap-phy-mux.c | 62 +++++++++++++++++++++++++++
> > drivers/clk/qcom/clk-regmap-phy-mux.h | 33 ++++++++++++++
> > 3 files changed, 96 insertions(+)
> > create mode 100644 drivers/clk/qcom/clk-regmap-phy-mux.c
> > create mode 100644 drivers/clk/qcom/clk-regmap-phy-mux.h
>
> Since it's posted as part of the series, I assume this should all be
> applied together, so I'll look for an ack from Bjorn Andersson
> <bjorn.andersson@linaro.org>, maintainer of drivers/clk/qcom.

Hi Bjorn,

Picking the clock patch through the clock tree would allow us to fix up
additional platforms (analog to patch 2 & 3) in time for v5.20 and
reduces risk for merge conflicts.

So please find an immutable branch (tag) of the clock patches here:
https://git.kernel.org/pub/scm/linux/kernel/git/qcom/linux.git
tags/20220608105238.2973600-1-dmitry.baryshkov@linaro.org

Hope this suits you.

Regards,
Bjorn