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Bugfix: use a dummy buffer for the inactive side of a transfer.

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This is especially important for writes.  SPI is inherently a bidirectional
bus; you receive data (even if it's garbage) while writing.  We should not
receive that data into the same buffer we're writing to the device.

When reading it doesn't matter what we send to the device, but using the
dummy buffer for that as well is pleasingly symmetrical.
This commit is contained in:
ian 2019-03-02 20:58:51 +00:00
parent 848287bd3d
commit a7b0a05518
1 changed files with 12 additions and 3 deletions
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15
sys/dev/flash/at45d.c
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@ -95,6 +95,7 @@ struct at45d_softc
uint16_t pagecount;
uint16_t pageoffset;
uint16_t pagesize;
void *dummybuf;
};
#define TSTATE_STOPPED 0
@ -285,6 +286,7 @@ at45d_detach(device_t dev)
if (err == 0 && sc->taskstate == TSTATE_STOPPED) {
disk_destroy(sc->disk);
bioq_flush(&sc->bio_queue, NULL, ENXIO);
free(sc->dummybuf, M_DEVBUF);
AT45D_LOCK_DESTROY(sc);
}
return (err);
@ -334,6 +336,8 @@ at45d_delayed_attach(void *xsc)
pagesize = ident->pagesize;
sc->pagesize = pagesize;
sc->dummybuf = malloc(pagesize, M_DEVBUF, M_WAITOK | M_ZERO);
sc->disk = disk_alloc();
sc->disk->d_open = at45d_open;
sc->disk->d_close = at45d_close;
@ -444,11 +448,13 @@ at45d_task(void *arg)
case BIO_READ:
txBuf[0] = CONTINUOUS_ARRAY_READ;
cmd.tx_cmd_sz = cmd.rx_cmd_sz = 8;
cmd.tx_data = cmd.rx_data = buf;
cmd.tx_data = sc->dummybuf;
cmd.rx_data = buf;
break;
case BIO_WRITE:
cmd.tx_cmd_sz = cmd.rx_cmd_sz = 4;
cmd.tx_data = cmd.rx_data = buf;
cmd.tx_data = buf;
cmd.rx_data = sc->dummybuf;
if (resid + offset > sc->pagesize)
len = sc->pagesize - offset;
break;
@ -524,7 +530,10 @@ at45d_task(void *arg)
len = sc->pagesize;
else
len = resid;
cmd.tx_data = cmd.rx_data = buf;
if (bp->bio_cmd == BIO_READ)
cmd.rx_data = buf;
else
cmd.tx_data = buf;
}
out:
if (berr != 0) {