drivers/ata/libata-pata-timings.c

Source file repositories/reference/linux-study-clean/drivers/ata/libata-pata-timings.c

File Facts

System
Linux kernel
Corpus path
drivers/ata/libata-pata-timings.c
Extension
.c
Size
5968 bytes
Lines
193
Domain
Driver Families
Bucket
drivers/ata
Inferred role
Driver Families: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

if (speed >= XFER_PIO_0 && speed < XFER_SW_DMA_0) {
			if (speed <= XFER_PIO_2)
				p.cycle = p.cyc8b = id[ATA_ID_EIDE_PIO];
			else if ((speed <= XFER_PIO_4) ||
				 (speed == XFER_PIO_5 && !ata_id_is_cfa(id)))
				p.cycle = p.cyc8b = id[ATA_ID_EIDE_PIO_IORDY];
		} else if (speed >= XFER_MW_DMA_0 && speed <= XFER_MW_DMA_2)
			p.cycle = id[ATA_ID_EIDE_DMA_MIN];

		ata_timing_merge(&p, t, t, ATA_TIMING_CYCLE | ATA_TIMING_CYC8B);
	}

	/*
	 * Convert the timing to bus clock counts.
	 */

	ata_timing_quantize(t, t, T, UT);

	/*
	 * Even in DMA/UDMA modes we still use PIO access for IDENTIFY,
	 * S.M.A.R.T * and some other commands. We have to ensure that the
	 * DMA cycle timing is slower/equal than the fastest PIO timing.
	 */

	if (speed > XFER_PIO_6) {
		ata_timing_compute(adev, adev->pio_mode, &p, T, UT);
		ata_timing_merge(&p, t, t, ATA_TIMING_ALL);
	}

	/*
	 * Lengthen active & recovery time so that cycle time is correct.
	 */

	if (t->act8b + t->rec8b < t->cyc8b) {
		t->act8b += (t->cyc8b - (t->act8b + t->rec8b)) / 2;
		t->rec8b = t->cyc8b - t->act8b;
	}

	if (t->active + t->recover < t->cycle) {
		t->active += (t->cycle - (t->active + t->recover)) / 2;
		t->recover = t->cycle - t->active;
	}

	/*
	 * In a few cases quantisation may produce enough errors to
	 * leave t->cycle too low for the sum of active and recovery
	 * if so we must correct this.
	 */
	if (t->active + t->recover > t->cycle)
		t->cycle = t->active + t->recover;

	return 0;
}
EXPORT_SYMBOL_GPL(ata_timing_compute);

Annotation

Implementation Notes