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Commit 9d60ef2b authored by Clemens Ladisch's avatar Clemens Ladisch Committed by Stefan Richter
Browse files

firewire: ohci: lazy bus time initialization 



The Bus_Time CSR is virtually never used, so we can avoid burning CPU in
interrupt context for 1 or 3 IsochronousCycleTimer accesses every minute
by not tracking the bus time until the CSR is actually accessed for the
first time.

Signed-off-by: default avatarClemens Ladisch <clemens@ladisch.de>
Signed-off-by: default avatarStefan Richter <stefanr@s5r6.in-berlin.de>
parent f07d42ac

drivers/firewire/ohci.c

+12 −6
Original line number Diff line number Diff line
@@ -191,6 +191,7 @@ struct fw_ohci { 
	unsigned quirks;

	unsigned int pri_req_max;

	u32 bus_time;

	bool bus_time_running;

	bool is_root;

	bool csr_state_setclear_abdicate;

	int n_ir;
@@ -1726,6 +1727,13 @@ static u32 update_bus_time(struct fw_ohci *ohci) 
{

	u32 cycle_time_seconds = get_cycle_time(ohci) >> 25;



	if (unlikely(!ohci->bus_time_running)) {

		reg_write(ohci, OHCI1394_IntMaskSet, OHCI1394_cycle64Seconds);

		ohci->bus_time = (lower_32_bits(get_seconds()) & ~0x7f) |

		                 (cycle_time_seconds & 0x40);

		ohci->bus_time_running = true;

	}



	if ((ohci->bus_time & 0x40) != (cycle_time_seconds & 0x40))

		ohci->bus_time += 0x40;
@@ -2213,7 +2221,7 @@ static int ohci_enable(struct fw_card *card, 
{

	struct fw_ohci *ohci = fw_ohci(card);

	struct pci_dev *dev = to_pci_dev(card->device);

	u32 lps, seconds, version, irqs;

	u32 lps, version, irqs;

	int i, ret;



	if (software_reset(ohci)) {
@@ -2269,9 +2277,7 @@ static int ohci_enable(struct fw_card *card, 
		  (OHCI1394_MAX_PHYS_RESP_RETRIES << 8) |

		  (200 << 16));



	seconds = lower_32_bits(get_seconds());

	reg_write(ohci, OHCI1394_IsochronousCycleTimer, seconds << 25);

	ohci->bus_time = seconds & ~0x3f;

	ohci->bus_time_running = false;



	version = reg_read(ohci, OHCI1394_Version) & 0x00ff00ff;

	if (version >= OHCI_VERSION_1_1) {
@@ -2369,7 +2375,6 @@ static int ohci_enable(struct fw_card *card, 
		OHCI1394_postedWriteErr |

		OHCI1394_selfIDComplete |

		OHCI1394_regAccessFail |

		OHCI1394_cycle64Seconds |

		OHCI1394_cycleInconsistent |

		OHCI1394_unrecoverableError |

		OHCI1394_cycleTooLong |
@@ -2658,7 +2663,8 @@ static void ohci_write_csr(struct fw_card *card, int csr_offset, u32 value) 


	case CSR_BUS_TIME:

		spin_lock_irqsave(&ohci->lock, flags);

		ohci->bus_time = (ohci->bus_time & 0x7f) | (value & ~0x7f);

		ohci->bus_time = (update_bus_time(ohci) & 0x40) |

		                 (value & ~0x7f);

		spin_unlock_irqrestore(&ohci->lock, flags);

		break;