Author: ian
Date: Sun Mar 31 23:24:04 2013
New Revision: 248963
URL: http://svnweb.freebsd.org/changeset/base/248963
Log:
Accommodate uart devices with large FIFOs (or DMA buffers which amount
to the same thing) by allocating the uart(4) rx buffer based on the
device's rxfifosz rather than using a hard-coded size of 384 bytes.
The historical 384 byte size is 3 times the largest hard-coded fifo
size in the tree, so use that ratio as a guide and allocate the buffer
as three times rxfifosz, but never smaller than the historical size.
Modified:
head/sys/dev/uart/uart_core.c
Modified: head/sys/dev/uart/uart_core.c
==============================================================================
--- head/sys/dev/uart/uart_core.c Sun Mar 31 22:43:16 2013
(r248962)
+++ head/sys/dev/uart/uart_core.c Sun Mar 31 23:24:04 2013
(r248963)
@@ -457,7 +457,13 @@ uart_bus_attach(device_t dev)
callout_init(&sc->sc_timer, 1);
}
- sc->sc_rxbufsz = 384;
+ /*
+ * Ensure there is room for at least three full FIFOs of data in the
+ * receive buffer (handles the case of low-level drivers with huge
+ * FIFOs), and also ensure that there is no less than the historical
+ * size of 384 bytes (handles the typical small-FIFO case).
+ */
+ sc->sc_rxbufsz = MAX(384, sc->sc_rxfifosz * 3);
sc->sc_rxbuf = malloc(sc->sc_rxbufsz * sizeof(*sc->sc_rxbuf),
M_UART, M_WAITOK);
sc->sc_txbuf = malloc(sc->sc_txfifosz * sizeof(*sc->sc_txbuf),
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