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

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Message-ID: <20231201032831.GA2898@thinkpad>
Date:   Fri, 1 Dec 2023 08:58:31 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Frank Li <Frank.li@....com>
Cc:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        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 Thu, Nov 30, 2023 at 03:17:39PM -0500, Frank Li wrote:
> On Thu, Nov 30, 2023 at 10:21:00PM +0530, Manivannan Sadhasivam wrote:
> > 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.
> 
> After read spec again, I think PEX is pci express. So it should software
> reset controller. I don't know what exactly did in the chip. But without
> below code, PCIe can't exit L2/L3.
> 
> Any harmful if dwc controller reset? Anyway these code works well with
> intel network card.

If it is a DWC controller reset, then we need to program all CSRs like DBI
etc... But from your reply it seems like the reset is limited to some module,
so it is fine.

- Mani

> 
> Frank
> 
> > 
> > - 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
> > > 
> > 
> > -- 
> > மணிவண்ணன் சதாசிவம்

-- 
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