Re: [PATCH v7 02/10] PCI: imx6: Add ref clock for i.MX95 PCIe

[Manivannan Sadhasivam <mani@kernel.org>]

On Mon, Jan 20, 2025 at 02:49:09AM +0000, Hongxing Zhu wrote:
> > -----Original Message-----
> > From: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> > Sent: 2025年1月19日 15:03
> > 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 v7 02/10] PCI: imx6: Add ref clock for i.MX95 PCIe
> > 
> > On Tue, Nov 26, 2024 at 03:56:54PM +0800, Richard Zhu wrote:
> > > Add "ref" clock to enable reference clock. To avoid breaking DT
> > > backwards compatibility, i.MX95 REF clock might be optional. Use
> > > devm_clk_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 | 16 +++++++++++-----
> > >  1 file changed, 11 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > > b/drivers/pci/controller/dwc/pci-imx6.c
> > > index 385f6323e3ca..f7e928e0a018 100644
> > > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > > @@ -103,6 +103,7 @@ 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]; @@ -1306,9 +1307,8
> > @@
> > > 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 i, ret, req_cnt;
> > >  	u16 val;
> > > -	int i;
> > >
> > >  	imx_pcie = devm_kzalloc(dev, sizeof(*imx_pcie), GFP_KERNEL);
> > >  	if (!imx_pcie)
> > > @@ -1358,9 +1358,13 @@ 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);
> > >  	if (ret)
> > >  		return ret;
> > > +	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);
> > 
> > I think you should just switch to devm_clk_bulk_get_all() instead of getting the
> > clks separately. As I told previously, the DT binding should ensure that correct
> > clocks for the platforms are defined in DT and the driver has no business in
> > validating it. Driver should trust the DT instead (unless there is a valid reason to not
> > do so).
> > 
> > >
> > >  	if (imx_check_flag(imx_pcie, IMX_PCIE_FLAG_HAS_PHYDRV)) {
> > >  		imx_pcie->phy = devm_phy_get(dev, "pcie-phy"); @@ -1509,6 +1513,7
> > > @@ 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"};
> > 
> > And these static clock defines will go away too.
> > 
> Hi Mani:
> Thanks for your comments.
> The suggestions are very nice. How about kick off further optimization later?

Sure. This series got merged already.

>  Since the changes would impact all i.MX PCIes.
> Meanwhile, I'm a little worry about that there is no consensus yet on relying
>  entirely on the dt binding check.

Consensus between whom?

- Mani

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