On Fri, Mar 17, 2023 at 04:05:28PM -0400, Frank Li wrote:
> From: Hou Zhiqiang <Zhiqiang.Hou@xxxxxxx>
>
> Add PME_Turn_Off/PME_TO_Ack handshake sequence, and finally
> put the PCIe controller into D3 state after the L2/L3 ready
> state transition process completion.
Can you please include a sentence or two about what this means for
devices below the PCIe controller? Is this guaranteed to be safe for
them, i.e., can all PCIe devices tolerate PME_Turn_Off, etc., and
resume correctly afterwards?
I suspect other drivers will copy this sort of pattern if it is safe
and useful.
> struct ls_pcie {
> struct dw_pcie *pci;
> + const struct ls_pcie_drvdata *drvdata;
> + void __iomem *pf_base;
> + void __iomem *lut_base;
> + bool big_endian;
> + bool ep_presence;
This means "any downstream device present", right? Could be an
Endpoint or could be a Switch Upstream Port? I guess it's basically a
cache of dw_pcie_link_up() at ls_pcie_host_init()-time.
> + bool pm_support;
> + struct regmap *scfg;
> + int index;
> };
> +static void ls1021a_pcie_send_turnoff_msg(struct ls_pcie *pcie)
> +{
> + u32 val;
> +
> + if (!pcie->scfg) {
> + dev_dbg(pcie->pci->dev, "SYSCFG is NULL\n");
> + return;
> + }
> +
> + /* Send Turn_off message */
> + regmap_read(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), &val);
> + val |= PMXMTTURNOFF;
> + regmap_write(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), val);
> +
> + /*
> + * Components with an upstream port must respond to
> + * PME_Turn_Off with PME_TO_Ack but we can't check.
> + *
> + * The standard recommends a 1-10ms timeout after which to
> + * proceed anyway as if acks were received.
Spec citation please.
> + */
> + mdelay(10);
> +
> + /* Clear Turn_off message */
> + regmap_read(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), &val);
> + val &= ~PMXMTTURNOFF;
> + regmap_write(pcie->scfg, SCFG_PEXPMWRCR(pcie->index), val);
> +}
> +static bool ls_pcie_pm_check(struct ls_pcie *pcie)
This is used as a boolean ("if (!ls_pcie_pm_check())") so it needs a
better name. "Check" doesn't give any hint about what a true or false
return value means. Something like "pm_supported" *would* give a
hint because "if (!ls_pcie_pm_supported())" is a sensible question to
ask.
> +{
> + if (!pcie->ep_presence) {
> + dev_dbg(pcie->pci->dev, "Endpoint isn't present\n");
> + return false;
> + }
> +
> + if (!pcie->pm_support)
> + return false;
Why test the negative ("!pcie->pm_support") and then return false?
How about:
if (pcie->pm_support)
return true;
return false;
or even better, just:
return pcie->pm_support;
> + return true;
> +}
