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

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Date:   Mon,  6 Jul 2020 11:31:15 +0200
From:   Saheed Olayemi Bolarinwa <refactormyself@...il.com>
To:     helgaas@...nel.org
Cc:     Bolarinwa Olayemi Saheed <refactormyself@...il.com>,
        bjorn@...gaas.com, skhan@...uxfoundation.org,
        linux-pci@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 5/11 RFC] PCI: pciehp: Make "Power On" the default 

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.

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