| Message ID | 20190110082633.6321-2-wens@csie.org (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | [1/2] pinctrl: sunxi: Increase size of regulator array | expand |
On Thu, Jan 10, 2019 at 04:26:33PM +0800, Chen-Yu Tsai wrote: > The new per-pin-bank regulator handling code in the sunxi pinctrl driver > has mismatched conditions for enabling and disabling the regulator: it > is enabled each time a pin is requested, but only disabled when the > pin-bank's reference count reaches zero. > > Since we are doing reference counting already, there's no need to enable > the regulator each time a pin is requested. Instead we can just do it > for the first requested pin of each pin-bank. Thus we can reverse the > test and bail out early if it's not the first occurrence. > > Fixes: 9a2a566adb00 ("pinctrl: sunxi: Deal with per-bank regulators") > Signed-off-by: Chen-Yu Tsai <wens@csie.org> Acked-by: Maxime Ripard <maxime.ripard@bootlin.com> > I'm getting the feeling that the current code is prone to race > conditions when pinctrl sets are actively switched during runtime, or > gpios are requested and freed from userspace. > > Any ideas? IIRC, I've looked into it when writing that patch and there's an upper mutex that prevents request from being called multiple times at once. Linus might prove me wrong though. Maxime
diff --git a/drivers/pinctrl/sunxi/pinctrl-sunxi.c b/drivers/pinctrl/sunxi/pinctrl-sunxi.c index 5d9184d18c16..9ad6e9c2adab 100644 --- a/drivers/pinctrl/sunxi/pinctrl-sunxi.c +++ b/drivers/pinctrl/sunxi/pinctrl-sunxi.c @@ -699,25 +699,21 @@ static int sunxi_pmx_request(struct pinctrl_dev *pctldev, unsigned offset) struct sunxi_pinctrl *pctl = pinctrl_dev_get_drvdata(pctldev); unsigned short bank = offset / PINS_PER_BANK; struct sunxi_pinctrl_regulator *s_reg = &pctl->regulators[bank]; - struct regulator *reg; + struct regulator *reg = s_reg->regulator; + char supply[16]; int ret; - reg = s_reg->regulator; - if (!reg) { - char supply[16]; - - snprintf(supply, sizeof(supply), "vcc-p%c", 'a' + bank); - reg = regulator_get(pctl->dev, supply); - if (IS_ERR(reg)) { - dev_err(pctl->dev, "Couldn't get bank P%c regulator\n", - 'A' + bank); - return PTR_ERR(reg); - } - - s_reg->regulator = reg; - refcount_set(&s_reg->refcount, 1); - } else { + if (reg) { refcount_inc(&s_reg->refcount); + return 0; + } + + snprintf(supply, sizeof(supply), "vcc-p%c", 'a' + bank); + reg = regulator_get(pctl->dev, supply); + if (IS_ERR(reg)) { + dev_err(pctl->dev, "Couldn't get bank P%c regulator\n", + 'A' + bank); + return PTR_ERR(reg); } ret = regulator_enable(reg); @@ -727,13 +723,13 @@ static int sunxi_pmx_request(struct pinctrl_dev *pctldev, unsigned offset) goto out; } + s_reg->regulator = reg; + refcount_set(&s_reg->refcount, 1); + return 0; out: - if (refcount_dec_and_test(&s_reg->refcount)) { - regulator_put(s_reg->regulator); - s_reg->regulator = NULL; - } + regulator_put(s_reg->regulator); return ret; }
The new per-pin-bank regulator handling code in the sunxi pinctrl driver has mismatched conditions for enabling and disabling the regulator: it is enabled each time a pin is requested, but only disabled when the pin-bank's reference count reaches zero. Since we are doing reference counting already, there's no need to enable the regulator each time a pin is requested. Instead we can just do it for the first requested pin of each pin-bank. Thus we can reverse the test and bail out early if it's not the first occurrence. Fixes: 9a2a566adb00 ("pinctrl: sunxi: Deal with per-bank regulators") Signed-off-by: Chen-Yu Tsai <wens@csie.org> --- I'm getting the feeling that the current code is prone to race conditions when pinctrl sets are actively switched during runtime, or gpios are requested and freed from userspace. Any ideas? --- drivers/pinctrl/sunxi/pinctrl-sunxi.c | 36 ++++++++++++--------------- 1 file changed, 16 insertions(+), 20 deletions(-)