linux-kernel - Re: [PATCH 5/11 RFC] PCI: pciehp: Make "Power On" the default

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Message-ID: <20200710001406.GA30420@bjorn-Precision-5520>
Date:   Thu, 9 Jul 2020 19:14:06 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Saheed Olayemi Bolarinwa <refactormyself@...il.com>
Cc:     bjorn@...gaas.com, skhan@...uxfoundation.org,
        linux-pci@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/11 RFC] PCI: pciehp: Make "Power On" the default

On Mon, Jul 06, 2020 at 11:31:15AM +0200, Saheed Olayemi Bolarinwa wrote:
> From: Bolarinwa Olayemi Saheed <refactormyself@...il.com>
> 
> The default case of the switch statement is redundant since 
> PCI_EXP_SLTCTL_PCC is only a single bit. pcie_capability_read_word()
> currently causes "On" value to be set if it fails. Patch 11/11
> changes the behaviour of pcie_capability_read_word() so on falure the
> "Off" value will be set.

s/falure/failure/

Split this into two patches.  The removal of the default case should
be in its own patch to make it trivial to review.

> Make the function set status to "Power On" by default and only set to
> Set "Power Off" only if pcie_capability_read_word() is successful and
> (slot_ctrl & PCI_EXP_SLTCTL_PCC) == PCI_EXP_SLTCTL_PWR_OFF. 
> 
> Suggested-by: Bjorn Helgaas <bjorn@...gaas.com>
> Signed-off-by: Bolarinwa Olayemi Saheed <refactormyself@...il.com>
> ---
>  drivers/pci/hotplug/pciehp_hpc.c | 16 +++++-----------
>  1 file changed, 5 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index 0b691e37fd04..78f806a9c6f1 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -399,22 +399,16 @@ void pciehp_get_power_status(struct controller *ctrl, u8 *status)
>  {
>  	struct pci_dev *pdev = ctrl_dev(ctrl);
>  	u16 slot_ctrl;
> +	int ret;
>  
> -	pcie_capability_read_word(pdev, PCI_EXP_SLTCTL, &slot_ctrl);
> +	*status = 1;	/* On */
> +	ret = pcie_capability_read_word(pdev, PCI_EXP_SLTCTL, &slot_ctrl);
>  	ctrl_dbg(ctrl, "%s: SLOTCTRL %x value read %x\n", __func__,
>  		 pci_pcie_cap(ctrl->pcie->port) + PCI_EXP_SLTCTL, slot_ctrl);
>  
> -	switch (slot_ctrl & PCI_EXP_SLTCTL_PCC) {
> -	case PCI_EXP_SLTCTL_PWR_ON:
> -		*status = 1;	/* On */
> -		break;
> -	case PCI_EXP_SLTCTL_PWR_OFF:
> +	if (!ret &&
> +	    ((slot_ctrl & PCI_EXP_SLTCTL_PCC) == PCI_EXP_SLTCTL_PWR_OFF))
>  		*status = 0;	/* Off */
> -		break;
> -	default:
> -		*status = 0xFF;
> -		break;
> -	}
>  }
>  
>  void pciehp_get_latch_status(struct controller *ctrl, u8 *status)
> -- 
> 2.18.2
>