linux-kernel - Re: [PATCH v4 4/4] PCI: layerscape: Add suspend/resume for ls1043a

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Message-ID: <20231130165100.GV3043@thinkpad>
Date:   Thu, 30 Nov 2023 22:21:00 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Frank Li <Frank.Li@....com>
Cc:     bhelgaas@...gle.com, imx@...ts.linux.dev, kw@...ux.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        lpieralisi@...nel.org, minghuan.Lian@....com, mingkai.hu@....com,
        robh@...nel.org, roy.zang@....com
Subject: Re: [PATCH v4 4/4] PCI: layerscape: Add suspend/resume for ls1043a

On Wed, Nov 29, 2023 at 04:44:12PM -0500, Frank Li wrote:
> In the suspend path, PME_Turn_Off message is sent to the endpoint to
> transition the link to L2/L3_Ready state. In this SoC, there is no way to
> check if the controller has received the PME_To_Ack from the endpoint or
> not. So to be on the safer side, the driver just waits for
> PCIE_PME_TO_L2_TIMEOUT_US before asserting the SoC specific PMXMTTURNOFF
> bit to complete the PME_Turn_Off handshake. This link would then enter
> L2/L3 state depending on the VAUX supply.
> 
> In the resume path, the link is brought back from L2 to L0 by doing a
> software reset.
> 

Same comment on the patch description as on patch 2/4.

> Signed-off-by: Frank Li <Frank.Li@....com>
> ---
> 
> Notes:
>     Change from v3 to v4
>     - Call scfg_pcie_send_turnoff_msg() shared with ls1021a
>     - update commit message
>     
>     Change from v2 to v3
>     - Remove ls_pcie_lut_readl(writel) function
>     
>     Change from v1 to v2
>     - Update subject 'a' to 'A'
> 
>  drivers/pci/controller/dwc/pci-layerscape.c | 63 ++++++++++++++++++++-
>  1 file changed, 62 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-layerscape.c b/drivers/pci/controller/dwc/pci-layerscape.c
> index 590e07bb27002..d39700b3afaaa 100644
> --- a/drivers/pci/controller/dwc/pci-layerscape.c
> +++ b/drivers/pci/controller/dwc/pci-layerscape.c
> @@ -41,6 +41,15 @@
>  #define SCFG_PEXSFTRSTCR	0x190
>  #define PEXSR(idx)		BIT(idx)
>  
> +/* LS1043A PEX PME control register */
> +#define SCFG_PEXPMECR		0x144
> +#define PEXPME(idx)		BIT(31 - (idx) * 4)
> +
> +/* LS1043A PEX LUT debug register */
> +#define LS_PCIE_LDBG	0x7fc
> +#define LDBG_SR		BIT(30)
> +#define LDBG_WE		BIT(31)
> +
>  #define PCIE_IATU_NUM		6
>  
>  struct ls_pcie_drvdata {
> @@ -225,6 +234,45 @@ static int ls1021a_pcie_exit_from_l2(struct dw_pcie_rp *pp)
>  	return scfg_pcie_exit_from_l2(pcie->scfg, SCFG_PEXSFTRSTCR, PEXSR(pcie->index));
>  }
>  
> +static void ls1043a_pcie_send_turnoff_msg(struct dw_pcie_rp *pp)
> +{
> +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> +	struct ls_pcie *pcie = to_ls_pcie(pci);
> +
> +	scfg_pcie_send_turnoff_msg(pcie->scfg, SCFG_PEXPMECR, PEXPME(pcie->index));
> +}
> +
> +static int ls1043a_pcie_exit_from_l2(struct dw_pcie_rp *pp)
> +{
> +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> +	struct ls_pcie *pcie = to_ls_pcie(pci);
> +	u32 val;
> +
> +	/*
> +	 * Only way let PEX module exit L2 is do a software reset.

Can you expand PEX? What is it used for?

Also if the reset is only for the PEX module, please use the same comment in
both patches 2 and 4. Patch 2 doesn't mention PEX in the comment.

- Mani

> +	 * LDBG_WE: allows the user to have write access to the PEXDBG[SR] for both setting and
> +	 *	    clearing the soft reset on the PEX module.
> +	 * LDBG_SR: When SR is set to 1, the PEX module enters soft reset.
> +	 */
> +	val = ls_pcie_pf_lut_readl(pcie, LS_PCIE_LDBG);
> +	val |= LDBG_WE;
> +	ls_pcie_pf_lut_writel(pcie, LS_PCIE_LDBG, val);
> +
> +	val = ls_pcie_pf_lut_readl(pcie, LS_PCIE_LDBG);
> +	val |= LDBG_SR;
> +	ls_pcie_pf_lut_writel(pcie, LS_PCIE_LDBG, val);
> +
> +	val = ls_pcie_pf_lut_readl(pcie, LS_PCIE_LDBG);
> +	val &= ~LDBG_SR;
> +	ls_pcie_pf_lut_writel(pcie, LS_PCIE_LDBG, val);
> +
> +	val = ls_pcie_pf_lut_readl(pcie, LS_PCIE_LDBG);
> +	val &= ~LDBG_WE;
> +	ls_pcie_pf_lut_writel(pcie, LS_PCIE_LDBG, val);
> +
> +	return 0;
> +}
> +
>  static const struct dw_pcie_host_ops ls_pcie_host_ops = {
>  	.host_init = ls_pcie_host_init,
>  	.pme_turn_off = ls_pcie_send_turnoff_msg,
> @@ -242,6 +290,19 @@ static const struct ls_pcie_drvdata ls1021a_drvdata = {
>  	.exit_from_l2 = ls1021a_pcie_exit_from_l2,
>  };
>  
> +static const struct dw_pcie_host_ops ls1043a_pcie_host_ops = {
> +	.host_init = ls_pcie_host_init,
> +	.pme_turn_off = ls1043a_pcie_send_turnoff_msg,
> +};
> +
> +static const struct ls_pcie_drvdata ls1043a_drvdata = {
> +	.pf_lut_off = 0x10000,
> +	.pm_support = true,
> +	.scfg_support = true,
> +	.ops = &ls1043a_pcie_host_ops,
> +	.exit_from_l2 = ls1043a_pcie_exit_from_l2,
> +};
> +
>  static const struct ls_pcie_drvdata layerscape_drvdata = {
>  	.pf_lut_off = 0xc0000,
>  	.pm_support = true,
> @@ -252,7 +313,7 @@ static const struct of_device_id ls_pcie_of_match[] = {
>  	{ .compatible = "fsl,ls1012a-pcie", .data = &layerscape_drvdata },
>  	{ .compatible = "fsl,ls1021a-pcie", .data = &ls1021a_drvdata },
>  	{ .compatible = "fsl,ls1028a-pcie", .data = &layerscape_drvdata },
> -	{ .compatible = "fsl,ls1043a-pcie", .data = &ls1021a_drvdata },
> +	{ .compatible = "fsl,ls1043a-pcie", .data = &ls1043a_drvdata },
>  	{ .compatible = "fsl,ls1046a-pcie", .data = &layerscape_drvdata },
>  	{ .compatible = "fsl,ls2080a-pcie", .data = &layerscape_drvdata },
>  	{ .compatible = "fsl,ls2085a-pcie", .data = &layerscape_drvdata },
> -- 
> 2.34.1
> 

-- 
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