linux-kernel - Re: [PATCH v4 2/9] PCI: imx6: Add ref clock for i.MX95 PCIe

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Message-ID: <20241022164603.gndz4vgbm2sgwtfj@thinkpad>
Date: Tue, 22 Oct 2024 22:16:03 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Richard Zhu <hongxing.zhu@....com>
Cc: kw@...ux.com, bhelgaas@...gle.com, lpieralisi@...nel.org,
	frank.li@....com, l.stach@...gutronix.de, robh+dt@...nel.org,
	conor+dt@...nel.org, shawnguo@...nel.org,
	krzysztof.kozlowski+dt@...aro.org, festevam@...il.com,
	s.hauer@...gutronix.de, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, kernel@...gutronix.de,
	imx@...ts.linux.dev
Subject: Re: [PATCH v4 2/9] PCI: imx6: Add ref clock for i.MX95 PCIe

On Tue, Oct 15, 2024 at 04:33:26PM +0800, Richard Zhu wrote:
> Add "ref" clock to enable reference clock.
> 
> 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.
> 

So this means the driver won't work with old devicetrees. Am I right? Then you
are breaking the DT compatibility.

You should make the clock optional in the driver.

- Mani

> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> Reviewed-by: Frank Li <Frank.Li@....com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 808d1f105417..52a8b2dc828a 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -1480,6 +1480,7 @@ 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] = {
> @@ -1593,8 +1594,8 @@ 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),
> +		.clk_names = imx95_clks,
> +		.clks_cnt = ARRAY_SIZE(imx95_clks),
>  		.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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