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hw/gpio/pl061: Honour Luminary PL061 PUR and PDR registers 

The Luminary variant of the PL061 has registers GPIOPUR and GPIOPDR
which lets the guest configure whether the GPIO lines are pull-up,
pull-down, or truly floating. Instead of assuming all lines are pulled
high, honour the PUR and PDR registers.

For the plain PL061, continue to assume that lines have an external
pull-up resistor, as we did before.

The stellaris board actually relies on this behaviour -- the CD line
of the ssd0323 display device is connected to GPIO output C7, and it
is only because of a different bug which we're about to fix that we
weren't incorrectly driving this line high on reset and putting the
ssd0323 into data mode.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Peter Maydell 2021-07-02 11:40:13 +01:00
parent 455736df2c
commit ad06d56fc7
2 changed files with 55 additions and 5 deletions
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58
hw/gpio/pl061.c
View File

@ -94,18 +94,68 @@ static const VMStateDescription vmstate_pl061 = {
}
};
static uint8_t pl061_floating(PL061State *s)
{
/*
* Return mask of bits which correspond to pins configured as inputs
* and which are floating (neither pulled up to 1 nor down to 0).
*/
uint8_t floating;
if (s->id == pl061_id_luminary) {
/*
* If both PUR and PDR bits are clear, there is neither a pullup
* nor a pulldown in place, and the output truly floats.
*/
floating = ~(s->pur | s->pdr);
} else {
/* Assume outputs are pulled high. FIXME: this is board dependent. */
floating = 0;
}
return floating & ~s->dir;
}
static uint8_t pl061_pullups(PL061State *s)
{
/*
* Return mask of bits which correspond to pins configured as inputs
* and which are pulled up to 1.
*/
uint8_t pullups;
if (s->id == pl061_id_luminary) {
/*
* The Luminary variant of the PL061 has an extra registers which
* the guest can use to configure whether lines should be pullup
* or pulldown.
*/
pullups = s->pur;
} else {
/* Assume outputs are pulled high. FIXME: this is board dependent. */
pullups = 0xff;
}
return pullups & ~s->dir;
}
static void pl061_update(PL061State *s)
{
uint8_t changed;
uint8_t mask;
uint8_t out;
int i;
uint8_t pullups = pl061_pullups(s);
uint8_t floating = pl061_floating(s);
trace_pl061_update(DEVICE(s)->canonical_path, s->dir, s->data);
trace_pl061_update(DEVICE(s)->canonical_path, s->dir, s->data,
pullups, floating);
/* Outputs float high. */
/* FIXME: This is board dependent. */
out = (s->data & s->dir) | ~s->dir;
/*
* Pins configured as output are driven from the data register;
* otherwise if they're pulled up they're 1, and if they're floating
* then we give them the same value they had previously, so we don't
* report any change to the other end.
*/
out = (s->data & s->dir) | pullups | (s->old_out_data & floating);
changed = s->old_out_data ^ out;
if (changed) {
s->old_out_data = out;

2
hw/gpio/trace-events
View File

@ -14,7 +14,7 @@ nrf51_gpio_set(int64_t line, int64_t value) "line %" PRIi64 " value %" PRIi64
nrf51_gpio_update_output_irq(int64_t line, int64_t value) "line %" PRIi64 " value %" PRIi64
# pl061.c
pl061_update(const char *id, uint32_t dir, uint32_t data) "%s GPIODIR 0x%x GPIODATA 0x%x"
pl061_update(const char *id, uint32_t dir, uint32_t data, uint32_t pullups, uint32_t floating) "%s GPIODIR 0x%x GPIODATA 0x%x pullups 0x%x floating 0x%x"
pl061_set_output(const char *id, int gpio, int level) "%s setting output %d to %d"
pl061_input_change(const char *id, int gpio, int level) "%s input %d changed to %d"
pl061_update_istate(const char *id, uint32_t istate, uint32_t im, int level) "%s GPIORIS 0x%x GPIOIE 0x%x interrupt level %d"