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: Clemens Ladisch <clemens@ladisch.de> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
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@ -191,6 +191,7 @@ struct fw_ohci {
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unsigned quirks;
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unsigned int pri_req_max;
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u32 bus_time;
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bool bus_time_running;
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bool is_root;
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bool csr_state_setclear_abdicate;
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int n_ir;
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@ -1726,6 +1727,13 @@ static u32 update_bus_time(struct fw_ohci *ohci)
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{
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u32 cycle_time_seconds = get_cycle_time(ohci) >> 25;
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if (unlikely(!ohci->bus_time_running)) {
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reg_write(ohci, OHCI1394_IntMaskSet, OHCI1394_cycle64Seconds);
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ohci->bus_time = (lower_32_bits(get_seconds()) & ~0x7f) |
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(cycle_time_seconds & 0x40);
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ohci->bus_time_running = true;
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}
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if ((ohci->bus_time & 0x40) != (cycle_time_seconds & 0x40))
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ohci->bus_time += 0x40;
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@ -2213,7 +2221,7 @@ static int ohci_enable(struct fw_card *card,
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{
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struct fw_ohci *ohci = fw_ohci(card);
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struct pci_dev *dev = to_pci_dev(card->device);
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u32 lps, seconds, version, irqs;
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u32 lps, version, irqs;
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int i, ret;
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if (software_reset(ohci)) {
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@ -2269,9 +2277,7 @@ static int ohci_enable(struct fw_card *card,
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(OHCI1394_MAX_PHYS_RESP_RETRIES << 8) |
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(200 << 16));
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seconds = lower_32_bits(get_seconds());
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reg_write(ohci, OHCI1394_IsochronousCycleTimer, seconds << 25);
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ohci->bus_time = seconds & ~0x3f;
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ohci->bus_time_running = false;
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version = reg_read(ohci, OHCI1394_Version) & 0x00ff00ff;
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if (version >= OHCI_VERSION_1_1) {
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@ -2369,7 +2375,6 @@ static int ohci_enable(struct fw_card *card,
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OHCI1394_postedWriteErr |
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OHCI1394_selfIDComplete |
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OHCI1394_regAccessFail |
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OHCI1394_cycle64Seconds |
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OHCI1394_cycleInconsistent |
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OHCI1394_unrecoverableError |
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OHCI1394_cycleTooLong |
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@ -2658,7 +2663,8 @@ static void ohci_write_csr(struct fw_card *card, int csr_offset, u32 value)
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case CSR_BUS_TIME:
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spin_lock_irqsave(&ohci->lock, flags);
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ohci->bus_time = (ohci->bus_time & 0x7f) | (value & ~0x7f);
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ohci->bus_time = (update_bus_time(ohci) & 0x40) |
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(value & ~0x7f);
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spin_unlock_irqrestore(&ohci->lock, flags);
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break;
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