Re: [PATCH v2 13/15] phy: qcom-qmp-pcie: add support for pipediv2 clock

[Dmitry Baryshkov]

On 20/10/2022 12:05, Johan Hovold wrote:
> On Thu, Oct 20, 2022 at 11:31:35AM +0300, Dmitry Baryshkov wrote:
> > On 19/10/2022 14:35, Johan Hovold wrote:
> > > Some QMP PHYs have a second fixed-divider pipe clock that needs to be
> > > enabled along with the pipe clock.
> > >
> > > Add support for an optional "pipediv2" clock.
> > >
> > > Signed-off-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
> > > ---
> > >    drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 42 ++++++++++++++++++++----
> > >    1 file changed, 36 insertions(+), 6 deletions(-)
>
> > I still think that the attached patch is somewhat simpler. Diffstat
> > supports that idea:
> >
> > $ diffstat /tmp/pipe.diff
> >    phy-qcom-qmp-pcie.c |   26 ++++++++++++++++----------
> >    1 file changed, 16 insertions(+), 10 deletions(-)
>
> It's not just about LoC.
>   
> > Yes, I'm speaking this after having cleaned up several open-coded
> > versions of clk_bulk_foo from the drm/msm code. It typically starts with
> > the 'just another clock' story, and then suddenly they are all over the
> > code.
>
> But you don't start using the bulk API when you have one clock. Two,
> maybe. Three, sure. It's a decision that needs to be done on a case-by
> case basis, and pipe clocks for the QMP block is different from general
> interface clocks (which are more likely to be extended). (And of course
> the clocks would need to be independent in the first place.)
>
> Here's your example diff inline:
>
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> index 9c8e009033f1..a148b143dd90 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> @@ -1378,8 +1378,10 @@ struct qmp_pcie {
>   	void __iomem *tx2;
>   	void __iomem *rx2;
>   
> -	struct clk *pipe_clk;
> +	struct clk_bulk_data *pipe_clks;
> +	int num_pipe_clks;
>   	struct clk_bulk_data *clks;
> +
>   	struct reset_control_bulk_data *resets;
>   	struct regulator_bulk_data *vregs;
>   
> @@ -1923,11 +1925,9 @@ static int qmp_pcie_power_on(struct phy *phy)
>   	qmp_pcie_init_registers(qmp, &cfg->tables);
>   	qmp_pcie_init_registers(qmp, mode_tables);
>   
> -	ret = clk_prepare_enable(qmp->pipe_clk);
> -	if (ret) {
> -		dev_err(qmp->dev, "pipe_clk enable failed err=%d\n", ret);
> +	ret = clk_bulk_prepare_enable(qmp->num_pipe_clks, qmp->pipe_clks);
> +	if (ret)
>   		return ret;
> -	}
>   
>   	/* Pull PHY out of reset state */
>   	qphy_clrbits(pcs, cfg->regs[QPHY_SW_RESET], SW_RESET);
> @@ -1950,7 +1950,7 @@ static int qmp_pcie_power_on(struct phy *phy)
>   	return 0;
>   
>   err_disable_pipe_clk:
> -	clk_disable_unprepare(qmp->pipe_clk);
> +	clk_bulk_disable_unprepare(qmp->num_pipe_clks, qmp->pipe_clks);
>   
>   	return ret;
>   }
> @@ -1960,7 +1960,7 @@ static int qmp_pcie_power_off(struct phy *phy)
>   	struct qmp_pcie *qmp = phy_get_drvdata(phy);
>   	const struct qmp_phy_cfg *cfg = qmp->cfg;
>   
> -	clk_disable_unprepare(qmp->pipe_clk);
> +	clk_bulk_disable_unprepare(qmp->num_pipe_clks, qmp->pipe_clks);
>   
>   	/* PHY reset */
>   	qphy_setbits(qmp->pcs, cfg->regs[QPHY_SW_RESET], SW_RESET);
>
> The above is pretty much identical, expect for using the bulk API
> instead of the very straight-forward pipe-clock helpers.
>
> @@ -2154,6 +2154,7 @@ static int qmp_pcie_parse_dt_legacy(struct qmp_pcie *qmp, struct device_node *np
>   	struct platform_device *pdev = to_platform_device(qmp->dev);
>   	const struct qmp_phy_cfg *cfg = qmp->cfg;
>   	struct device *dev = qmp->dev;
> +	struct clk *clk;
>   
>   	qmp->serdes = devm_platform_ioremap_resource(pdev, 0);
>   	if (IS_ERR(qmp->serdes))
> @@ -2206,12 +2207,17 @@ static int qmp_pcie_parse_dt_legacy(struct qmp_pcie *qmp, struct device_node *np
>   		}
>   	}
>   
> -	qmp->pipe_clk = devm_get_clk_from_child(dev, np, NULL);
> -	if (IS_ERR(qmp->pipe_clk)) {
> -		return dev_err_probe(dev, PTR_ERR(qmp->pipe_clk),
> +	clk = devm_get_clk_from_child(dev, np, NULL);
> +	if (IS_ERR(clk)) {
> +		return dev_err_probe(dev, PTR_ERR(clk),
>   				     "failed to get pipe clock\n");
>   	}
>   
> +	qmp->num_pipe_clks = 1;
> +	qmp->pipe_clks = devm_kcalloc(dev, qmp->num_pipe_clks,
> +				      sizeof(*qmp->pipe_clks), GFP_KERNEL);
> +	qmp->pipe_clks[0].clk = clk;
>
> So here you're poking at bulk API internals and forgot to set the id
> string, which the implementation uses.

I didn't forget, I just skipped setting it. Hmm. I thought that it is 
used only for clk_bulk_get. But after checking, it seems it's also used 
for error messages. Mea culpa.

But it's not that I was poking into the internals. These items are in 
the public header.

> For reasons like this, and the fact that will likely never have a third
> pipe clock, I'm reluctant to using the bulk API.

Let's resort to the maintainer opinion then.

> +
>   	return 0;
>   }
>   
> Johan

--
With best wishes
Dmitry