linux-kernel - Re: [PATCH v6 02/10] PCI: imx6: Add ref clock for i.MX95 PCIe

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Message-ID: <20241115063816.xpjqgm2j34enhe7s@thinkpad>
Date: Fri, 15 Nov 2024 12:08:16 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Richard Zhu <hongxing.zhu@....com>
Cc: l.stach@...gutronix.de, bhelgaas@...gle.com, lpieralisi@...nel.org,
	kw@...ux.com, robh@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, shawnguo@...nel.org, frank.li@....com,
	s.hauer@...gutronix.de, festevam@...il.com, imx@...ts.linux.dev,
	kernel@...gutronix.de, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.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"?

> 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@....com>
> Reviewed-by: Frank Li <Frank.Li@....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")

And who is going to supply the reference clock in the absence of this clockn in
DT?

- 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
> 

-- 
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