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Commit 3ea8197e authored by Stephen Hemminger's avatar Stephen Hemminger Committed by Bjorn Helgaas
Browse files

PCI: Remove unused Latency Tolerance Reporting support 



My philosophy is unused code is dead code.  And dead code is subject to bit
rot and is a likely source of bugs.  Use it or lose it.

This reverts 51c2e0a7 ("PCI: add latency tolerance reporting
enable/disable support"), removing these interfaces:

    pci_enable_ltr()
    pci_disable_ltr()
    pci_set_ltr()

[bhelgaas: split to separate patch, also remove prototypes from pci.h]
Signed-off-by: default avatarStephen Hemminger <stephen@networkplumber.org>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
CC: Jesse Barnes <jbarnes@virtuousgeek.org>
parent b340cacc

drivers/pci/pci.c

+0 −123
Original line number Diff line number Diff line
@@ -2223,129 +2223,6 @@ void pci_disable_obff(struct pci_dev *dev) 
}

EXPORT_SYMBOL(pci_disable_obff);



/**

 * pci_ltr_supported - check whether a device supports LTR

 * @dev: PCI device

 *

 * RETURNS:

 * True if @dev supports latency tolerance reporting, false otherwise.

 */

static bool pci_ltr_supported(struct pci_dev *dev)

{

	u32 cap;



	pcie_capability_read_dword(dev, PCI_EXP_DEVCAP2, &cap);



	return cap & PCI_EXP_DEVCAP2_LTR;

}



/**

 * pci_enable_ltr - enable latency tolerance reporting

 * @dev: PCI device

 *

 * Enable LTR on @dev if possible, which means enabling it first on

 * upstream ports.

 *

 * RETURNS:

 * Zero on success, errno on failure.

 */

int pci_enable_ltr(struct pci_dev *dev)

{

	int ret;



	/* Only primary function can enable/disable LTR */

	if (PCI_FUNC(dev->devfn) != 0)

		return -EINVAL;



	if (!pci_ltr_supported(dev))

		return -ENOTSUPP;



	/* Enable upstream ports first */

	if (dev->bus->self) {

		ret = pci_enable_ltr(dev->bus->self);

		if (ret)

			return ret;

	}



	return pcie_capability_set_word(dev, PCI_EXP_DEVCTL2,

					PCI_EXP_DEVCTL2_LTR_EN);

}

EXPORT_SYMBOL(pci_enable_ltr);



/**

 * pci_disable_ltr - disable latency tolerance reporting

 * @dev: PCI device

 */

void pci_disable_ltr(struct pci_dev *dev)

{

	/* Only primary function can enable/disable LTR */

	if (PCI_FUNC(dev->devfn) != 0)

		return;



	if (!pci_ltr_supported(dev))

		return;



	pcie_capability_clear_word(dev, PCI_EXP_DEVCTL2,

				   PCI_EXP_DEVCTL2_LTR_EN);

}

EXPORT_SYMBOL(pci_disable_ltr);



static int __pci_ltr_scale(int *val)

{

	int scale = 0;



	while (*val > 1023) {

		*val = (*val + 31) / 32;

		scale++;

	}

	return scale;

}



/**

 * pci_set_ltr - set LTR latency values

 * @dev: PCI device

 * @snoop_lat_ns: snoop latency in nanoseconds

 * @nosnoop_lat_ns: nosnoop latency in nanoseconds

 *

 * Figure out the scale and set the LTR values accordingly.

 */

int pci_set_ltr(struct pci_dev *dev, int snoop_lat_ns, int nosnoop_lat_ns)

{

	int pos, ret, snoop_scale, nosnoop_scale;

	u16 val;



	if (!pci_ltr_supported(dev))

		return -ENOTSUPP;



	snoop_scale = __pci_ltr_scale(&snoop_lat_ns);

	nosnoop_scale = __pci_ltr_scale(&nosnoop_lat_ns);



	if (snoop_lat_ns > PCI_LTR_VALUE_MASK ||

	    nosnoop_lat_ns > PCI_LTR_VALUE_MASK)

		return -EINVAL;



	if ((snoop_scale > (PCI_LTR_SCALE_MASK >> PCI_LTR_SCALE_SHIFT)) ||

	    (nosnoop_scale > (PCI_LTR_SCALE_MASK >> PCI_LTR_SCALE_SHIFT)))

		return -EINVAL;



	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR);

	if (!pos)

		return -ENOTSUPP;



	val = (snoop_scale << PCI_LTR_SCALE_SHIFT) | snoop_lat_ns;

	ret = pci_write_config_word(dev, pos + PCI_LTR_MAX_SNOOP_LAT, val);

	if (ret != 4)

		return -EIO;



	val = (nosnoop_scale << PCI_LTR_SCALE_SHIFT) | nosnoop_lat_ns;

	ret = pci_write_config_word(dev, pos + PCI_LTR_MAX_NOSNOOP_LAT, val);

	if (ret != 4)

		return -EIO;



	return 0;

}

EXPORT_SYMBOL(pci_set_ltr);



static int pci_acs_enable;



/**

include/linux/pci.h

+0 −4
Original line number Diff line number Diff line
@@ -1009,10 +1009,6 @@ enum pci_obff_signal_type { 
int pci_enable_obff(struct pci_dev *dev, enum pci_obff_signal_type);

void pci_disable_obff(struct pci_dev *dev);



int pci_enable_ltr(struct pci_dev *dev);

void pci_disable_ltr(struct pci_dev *dev);

int pci_set_ltr(struct pci_dev *dev, int snoop_lat_ns, int nosnoop_lat_ns);



/* For use by arch with custom probe code */

void set_pcie_port_type(struct pci_dev *pdev);

void set_pcie_hotplug_bridge(struct pci_dev *pdev);