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uart: Ingore pl011 historic mistakes

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Some veresions of EDK-II and QEMU reported the wrong values for the
register shift and the region I/O size. Detect those and set it to the
correct values. In general, anything other than a shift of 2 and a
regio width of 4 (bytes, or 32 bits) is a mistake. However, allow
for overrides in the future by only overriding the buggy values.
Otherwise, we will fail to boot.

PR:			282936
Sponsored by:		Netflix
Reviewed by:		emaste
Differential Revision:	https://reviews.freebsd.org/D47946
This commit is contained in:
Warner Losh 2025-01-14 19:17:46 -07:00
parent 02703de8bc
commit dea3eef94c
1 changed files with 23 additions and 1 deletions
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24
sys/dev/uart/uart_dev_pl011.c
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@ -172,6 +172,27 @@ static int
uart_pl011_probe(struct uart_bas *bas)
{
/*
* Versions of QEMU before 41f7b58b634e (8.3) reported bogus values for
* this tabel. The PL011 IP is always 32-bits wide and should be shifted
* 2 to match the 4-byte size of the data. QEMU reported these values
* incorrectly before that.
* https://github.com/qemu/qemu/commit/41f7b58b634ec3b60ae874375d2bbb61d790971e
*
* In additon, other hardware vendors also reported this value
* incorrectly. It's not tied to what the ACPI device node is, but was a
* misunderstanding coupled with a Linux driver that didn't need the
* right values. Quirks used to be used to ignore the bad values, now we
* detect the historic mistake and override (to allow for a future where
* we may need to override these values).
*
* PL011 Docs: https://developer.arm.com/documentation/ddi0183/latest/
*/
if (bas->regshft == 0 || bas->regiowidth == 1) {
bas->regshft = 2;
bas->regiowidth = 4;
}
return (0);
}
@ -356,7 +377,8 @@ static struct uart_class uart_pl011_class = {
.uc_ops = &uart_pl011_ops,
.uc_range = 0x48,
.uc_rclk = 0,
.uc_rshift = 2
.uc_rshift = 2,
.uc_riowidth = 4,
};
UART_CLASS(uart_pl011_class);