RE: [PATCH v6 02/10] PCI: imx6: Add ref clock for i.MX95 PCIe

[Hongxing Zhu <hongxing.zhu@nxp.com>]

> -----Original Message-----
> From: Hongxing Zhu
> Sent: 2024年11月18日 10:59
> To: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> Cc: l.stach@pengutronix.de; bhelgaas@google.com; lpieralisi@kernel.org;
> kw@linux.com; robh@kernel.org; krzk+dt@kernel.org; conor+dt@kernel.org;
> shawnguo@kernel.org; Frank Li <frank.li@nxp.com>; s.hauer@pengutronix.de;
> festevam@gmail.com; imx@lists.linux.dev; kernel@pengutronix.de;
> linux-pci@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: RE: [PATCH v6 02/10] PCI: imx6: Add ref clock for i.MX95 PCIe
> 
> > -----Original Message-----
> > From: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> > Sent: 2024年11月15日 14:38
> > To: Hongxing Zhu <hongxing.zhu@nxp.com>
> > Cc: l.stach@pengutronix.de; bhelgaas@google.com;
> > lpieralisi@kernel.org; kw@linux.com; robh@kernel.org;
> > krzk+dt@kernel.org; conor+dt@kernel.org; shawnguo@kernel.org; Frank Li
> > <frank.li@nxp.com>; s.hauer@pengutronix.de; festevam@gmail.com;
> > imx@lists.linux.dev; kernel@pengutronix.de; linux-pci@vger.kernel.org;
> > linux-arm-kernel@lists.infradead.org; devicetree@vger.kernel.org;
> > linux-kernel@vger.kernel.org
> > Subject: Re: [PATCH v6 02/10] PCI: imx6: Add ref clock for i.MX95 PCIe
> >
> > On Fri, Nov 01, 2024 at 03:06:02PM +0800, Richard Zhu wrote:
> > > Add "ref" clock to enable reference clock. To avoid the DT
> > > compatibility, i.MX95 REF clock might be optional.
> >
> > Your wording is not correct. Perhaps you wanted to say, "To avoid
> > breaking DT backwards compatibility"?
> >
> Yes, you're right. Thanks.
> 
> > > Replace the
> > > devm_clk_bulk_get() by devm_clk_bulk_get_optional() to fetch
> > > i.MX95 PCIe optional clocks in driver.
> > >
> > > If use external clock, ref clock should point to external reference.
> > >
> > > If use internal clock, CREF_EN in LAST_TO_REG controls reference
> > > output, which implement in drivers/clk/imx/clk-imx95-blk-ctl.c.
> > >
> > > Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
> > > Reviewed-by: Frank Li <Frank.Li@nxp.com>
> > > ---
> > >  drivers/pci/controller/dwc/pci-imx6.c | 19 +++++++++++++------
> > >  1 file changed, 13 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > > b/drivers/pci/controller/dwc/pci-imx6.c
> > > index 808d1f105417..bc8567677a67 100644
> > > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > > @@ -82,6 +82,7 @@ enum imx_pcie_variants {
> > >  #define IMX_PCIE_FLAG_HAS_SERDES		BIT(6)
> > >  #define IMX_PCIE_FLAG_SUPPORT_64BIT		BIT(7)
> > >  #define IMX_PCIE_FLAG_CPU_ADDR_FIXUP		BIT(8)
> > > +#define IMX_PCIE_FLAG_CUSTOM_PME_TURNOFF	BIT(9)
> > >
> > >  #define imx_check_flag(pci, val)	(pci->drvdata->flags & val)
> > >
> > > @@ -98,6 +99,7 @@ struct imx_pcie_drvdata {
> > >  	const char *gpr;
> > >  	const char * const *clk_names;
> > >  	const u32 clks_cnt;
> > > +	const u32 clks_optional_cnt;
> > >  	const u32 ltssm_off;
> > >  	const u32 ltssm_mask;
> > >  	const u32 mode_off[IMX_PCIE_MAX_INSTANCES]; @@ -1278,9
> +1280,8
> > @@
> > > static int imx_pcie_probe(struct platform_device *pdev)
> > >  	struct device_node *np;
> > >  	struct resource *dbi_base;
> > >  	struct device_node *node = dev->of_node;
> > > -	int ret;
> > > +	int ret, i, req_cnt;
> > >  	u16 val;
> > > -	int i;
> > >
> > >  	imx_pcie = devm_kzalloc(dev, sizeof(*imx_pcie), GFP_KERNEL);
> > >  	if (!imx_pcie)
> > > @@ -1330,7 +1331,10 @@ static int imx_pcie_probe(struct
> > platform_device *pdev)
> > >  		imx_pcie->clks[i].id = imx_pcie->drvdata->clk_names[i];
> > >
> > >  	/* Fetch clocks */
> > > -	ret = devm_clk_bulk_get(dev, imx_pcie->drvdata->clks_cnt,
> > imx_pcie->clks);
> > > +	req_cnt = imx_pcie->drvdata->clks_cnt -
> > imx_pcie->drvdata->clks_optional_cnt;
> > > +	ret = devm_clk_bulk_get(dev, req_cnt, imx_pcie->clks);
> > > +	ret |= devm_clk_bulk_get_optional(dev,
> > imx_pcie->drvdata->clks_optional_cnt,
> > > +					  imx_pcie->clks + req_cnt);
> >
> > Why do you need to use 'clk_bulk' API to get a single reference clock?
> > Just use devm_clk_get_optional(dev, "ref")
> It's easier to add more optional clks in future. I can change to use
> devm_clk_get_optional(dev, "ref") here if you insistent.
Since the clock fetch is not distinguished by platforms explicitly.
devm_clk_get_optional(dev, "ref") can be used only when i.MX95 specification
 is added.
-       ret |= devm_clk_bulk_get_optional(dev, imx_pcie->drvdata->clks_optional_cnt,
-                                         imx_pcie->clks + req_cnt);
        if (ret)
                return ret;
+       for (i = 0; i < imx_pcie->drvdata->clks_optional_cnt; i++) {
+               imx_pcie->clks[req_cnt + i].clk = devm_clk_get_optional(dev,
+                               imx_pcie->drvdata->clk_names[req_cnt + i]);
+               if (IS_ERR(imx_pcie->clks[req_cnt + i].clk))
+                       return PTR_ERR(imx_pcie->clks[req_cnt + i].clk);
+       }

Or
-       ret |= devm_clk_bulk_get_optional(dev, imx_pcie->drvdata->clks_optional_cnt,
-                                         imx_pcie->clks + req_cnt);
        if (ret)
                return ret;
+       if (imx_pcie->drvdata->variant == IMX95) {
+               imx_pcie->clks[req_cnt].clk = devm_clk_get_optional(dev, "ref");
+               if (IS_ERR(imx_pcie->clks[req_cnt].clk))
+                       return PTR_ERR(imx_pcie->clks[req_cnt].clk);
+       }

Which one is better of these two changes?
Or
To keep codes simple and aligned, how about to keep the original one?

Best Regards
Richard Zhu

> 
> >
> > And who is going to supply the reference clock in the absence of this
> > clockn in DT?
> When the "preview" version firmware is used, this clock is gated on in default.
> In this case, hiso-blk-ctrl would gated on this clock in default state.
> 
> Best Regards
> Richard Zhu
> >
> > - Mani
> >
> > >  	if (ret)
> > >  		return ret;
> > >
> > > @@ -1480,6 +1484,7 @@ static const char * const imx8mm_clks[] =
> > > {"pcie_bus", "pcie", "pcie_aux"};  static const char * const
> > > imx8mq_clks[] = {"pcie_bus", "pcie", "pcie_phy", "pcie_aux"};
> > > static const char * const imx6sx_clks[] = {"pcie_bus", "pcie",
> > > "pcie_phy", "pcie_inbound_axi"};  static const char * const
> > > imx8q_clks[] = {"mstr", "slv", "dbi"};
> > > +static const char * const imx95_clks[] = {"pcie_bus", "pcie",
> > > +"pcie_phy", "pcie_aux", "ref"};
> > >
> > >  static const struct imx_pcie_drvdata drvdata[] = {
> > >  	[IMX6Q] = {
> > > @@ -1592,9 +1597,11 @@ static const struct imx_pcie_drvdata
> > > drvdata[] =
> > {
> > >  	},
> > >  	[IMX95] = {
> > >  		.variant = IMX95,
> > > -		.flags = IMX_PCIE_FLAG_HAS_SERDES,
> > > -		.clk_names = imx8mq_clks,
> > > -		.clks_cnt = ARRAY_SIZE(imx8mq_clks),
> > > +		.flags = IMX_PCIE_FLAG_HAS_SERDES |
> > > +			 IMX_PCIE_FLAG_SUPPORTS_SUSPEND,
> > > +		.clk_names = imx95_clks,
> > > +		.clks_cnt = ARRAY_SIZE(imx95_clks),
> > > +		.clks_optional_cnt = 1,
> > >  		.ltssm_off = IMX95_PE0_GEN_CTRL_3,
> > >  		.ltssm_mask = IMX95_PCIE_LTSSM_EN,
> > >  		.mode_off[0]  = IMX95_PE0_GEN_CTRL_1,
> > > --
> > > 2.37.1
> > >
> >
> > --
> > மணிவண்ணன் சதாசிவம்