ahci_xgene: Implement the workaround to fix the missing of the edge interrupt for the HOST_IRQ_STAT.
Due to H/W errata, the HOST_IRQ_STAT register misses the edge interrupt when clearing the HOST_IRQ_STAT register and hardware reporting the PORT_IRQ_STAT register happens to be at the same clock cycle. Signed-off-by: Suman Tripathi <stripathi@apm.com> Signed-off-by: Tejun Heo <tj@kernel.org>
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@ -548,6 +548,51 @@ softreset_retry:
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return rc;
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}
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/**
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* xgene_ahci_handle_broken_edge_irq - Handle the broken irq.
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* @ata_host: Host that recieved the irq
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* @irq_masked: HOST_IRQ_STAT value
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*
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* For hardware with broken edge trigger latch
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* the HOST_IRQ_STAT register misses the edge interrupt
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* when clearing of HOST_IRQ_STAT register and hardware
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* reporting the PORT_IRQ_STAT register at the
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* same clock cycle.
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* As such, the algorithm below outlines the workaround.
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*
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* 1. Read HOST_IRQ_STAT register and save the state.
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* 2. Clear the HOST_IRQ_STAT register.
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* 3. Read back the HOST_IRQ_STAT register.
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* 4. If HOST_IRQ_STAT register equals to zero, then
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* traverse the rest of port's PORT_IRQ_STAT register
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* to check if an interrupt is triggered at that point else
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* go to step 6.
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* 5. If PORT_IRQ_STAT register of rest ports is not equal to zero
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* then update the state of HOST_IRQ_STAT saved in step 1.
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* 6. Handle port interrupts.
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* 7. Exit
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*/
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static int xgene_ahci_handle_broken_edge_irq(struct ata_host *host,
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u32 irq_masked)
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{
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struct ahci_host_priv *hpriv = host->private_data;
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void __iomem *port_mmio;
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int i;
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if (!readl(hpriv->mmio + HOST_IRQ_STAT)) {
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for (i = 0; i < host->n_ports; i++) {
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if (irq_masked & (1 << i))
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continue;
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port_mmio = ahci_port_base(host->ports[i]);
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if (readl(port_mmio + PORT_IRQ_STAT))
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irq_masked |= (1 << i);
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}
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}
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return ahci_handle_port_intr(host, irq_masked);
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}
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static irqreturn_t xgene_ahci_irq_intr(int irq, void *dev_instance)
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{
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struct ata_host *host = dev_instance;
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@ -576,7 +621,7 @@ static irqreturn_t xgene_ahci_irq_intr(int irq, void *dev_instance)
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*/
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writel(irq_stat, mmio + HOST_IRQ_STAT);
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rc = ahci_handle_port_intr(host, irq_masked);
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rc = xgene_ahci_handle_broken_edge_irq(host, irq_masked);
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spin_unlock(&host->lock);
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