* [PATCH v3 1/3] irqchip: qcom-pdc: Fix phantom irq when changing between rising/falling @ 2020-12-10 0:41 Douglas Anderson 2020-12-10 0:41 ` [PATCH v3 2/3] pinctrl: qcom: Allow SoCs to specify a GPIO function that's not 0 Douglas Anderson ` (2 more replies) 0 siblings, 3 replies; 7+ messages in thread From: Douglas Anderson @ 2020-12-10 0:41 UTC (permalink / raw) To: Marc Zyngier, Thomas Gleixner, Jason Cooper, Linus Walleij Cc: linux-arm-msm, Bjorn Andersson, Srinivas Ramana, Maulik Shah, Stephen Boyd, Neeraj Upadhyay, Rajendra Nayak, linux-gpio, Douglas Anderson, Andy Gross, Archana Sathyakumar, Lina Iyer, linux-kernel We have a problem if we use gpio-keys and configure wakeups such that we only want one edge to wake us up. AKA: wakeup-event-action = <EV_ACT_DEASSERTED>; wakeup-source; Specifically we end up with a phantom interrupt that blocks suspend if the line was already high and we want wakeups on rising edges (AKA we want the GPIO to go low and then high again before we wake up). The opposite is also problematic. Specifically, here's what's happening today: 1. Normally, gpio-keys configures to look for both edges. Due to the current workaround introduced in commit c3c0c2e18d94 ("pinctrl: qcom: Handle broken/missing PDC dual edge IRQs on sc7180"), if the line was high we'd configure for falling edges. 2. At suspend time, we change to look for rising edges. 3. After qcom_pdc_gic_set_type() runs, we get a phantom interrupt. We can solve this by just clearing the phantom interrupt. NOTE: it is possible that this could cause problems for a client with very specific needs, but there's not much we can do with this hardware. As an example, let's say the interrupt signal is currently high and the client is looking for falling edges. The client now changes to look for rising edges. The client could possibly expect that if the line has a short pulse low (and back high) that it would always be detected. Specifically no matter when the pulse happened, it should either have tripped the (old) falling edge trigger or the (new) rising edge trigger. We will simply not trip it. We could narrow down the race a bit by polling our parent before changing types, but no matter what we do there will still be a period of time where we can't tell the difference between a real transition (or more than one transition) and the phantom. Fixes: f55c73aef890 ("irqchip/pdc: Add PDC interrupt controller for QCOM SoCs") Signed-off-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Maulik Shah <mkshah@codeaurora.org> Tested-by: Maulik Shah <mkshah@codeaurora.org> --- There are no dependencies between this patch and patch #2/#3. It can go in by itself. Patches are only grouped together in one series because they address similar issues. Maulik has got confirmation from hardware guys and understands the problem. This patch is ready to land. Changes in v3: - Adjusted the comment as per Maulik. Changes in v2: - 0 => false - If irq_chip_set_type_parent() fails don't bother clearing. - Add Fixes tag. drivers/irqchip/qcom-pdc.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/drivers/irqchip/qcom-pdc.c b/drivers/irqchip/qcom-pdc.c index bd39e9de6ecf..5dc63c20b67e 100644 --- a/drivers/irqchip/qcom-pdc.c +++ b/drivers/irqchip/qcom-pdc.c @@ -159,6 +159,8 @@ static int qcom_pdc_gic_set_type(struct irq_data *d, unsigned int type) { int pin_out = d->hwirq; enum pdc_irq_config_bits pdc_type; + enum pdc_irq_config_bits old_pdc_type; + int ret; if (pin_out == GPIO_NO_WAKE_IRQ) return 0; @@ -187,9 +189,26 @@ static int qcom_pdc_gic_set_type(struct irq_data *d, unsigned int type) return -EINVAL; } + old_pdc_type = pdc_reg_read(IRQ_i_CFG, pin_out); pdc_reg_write(IRQ_i_CFG, pin_out, pdc_type); - return irq_chip_set_type_parent(d, type); + ret = irq_chip_set_type_parent(d, type); + if (ret) + return ret; + + /* + * When we change types the PDC can give a phantom interrupt. + * Clear it. Specifically the phantom shows up when reconfiguring + * polarity of interrupt without changing the state of the signal + * but let's be consistent and clear it always. + * + * Doing this works because we have IRQCHIP_SET_TYPE_MASKED so the + * interrupt will be cleared before the rest of the system sees it. + */ + if (old_pdc_type != pdc_type) + irq_chip_set_parent_state(d, IRQCHIP_STATE_PENDING, false); + + return 0; } static struct irq_chip qcom_pdc_gic_chip = { -- 2.29.2.576.ga3fc446d84-goog ^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH v3 2/3] pinctrl: qcom: Allow SoCs to specify a GPIO function that's not 0 2020-12-10 0:41 [PATCH v3 1/3] irqchip: qcom-pdc: Fix phantom irq when changing between rising/falling Douglas Anderson @ 2020-12-10 0:41 ` Douglas Anderson 2020-12-10 21:06 ` Stephen Boyd 2020-12-10 0:41 ` [PATCH v3 3/3] pinctrl: qcom: Clear possible pending irq when remuxing GPIOs Douglas Anderson 2020-12-10 21:11 ` [PATCH v3 1/3] irqchip: qcom-pdc: Fix phantom irq when changing between rising/falling Stephen Boyd 2 siblings, 1 reply; 7+ messages in thread From: Douglas Anderson @ 2020-12-10 0:41 UTC (permalink / raw) To: Marc Zyngier, Thomas Gleixner, Jason Cooper, Linus Walleij Cc: linux-arm-msm, Bjorn Andersson, Srinivas Ramana, Maulik Shah, Stephen Boyd, Neeraj Upadhyay, Rajendra Nayak, linux-gpio, Douglas Anderson, Andy Gross, linux-kernel There's currently a comment in the code saying function 0 is GPIO. Instead of hardcoding it, let's add a member where an SoC can specify it. No known SoCs use a number other than 0, but this just makes the code clearer. NOTE: no SoC code needs to be updated since we can rely on zero-initialization. Signed-off-by: Douglas Anderson <dianders@chromium.org> --- (no changes since v1) drivers/pinctrl/qcom/pinctrl-msm.c | 4 ++-- drivers/pinctrl/qcom/pinctrl-msm.h | 2 ++ 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/pinctrl/qcom/pinctrl-msm.c b/drivers/pinctrl/qcom/pinctrl-msm.c index 77a25bdf0da7..588df91274e2 100644 --- a/drivers/pinctrl/qcom/pinctrl-msm.c +++ b/drivers/pinctrl/qcom/pinctrl-msm.c @@ -210,8 +210,8 @@ static int msm_pinmux_request_gpio(struct pinctrl_dev *pctldev, if (!g->nfuncs) return 0; - /* For now assume function 0 is GPIO because it always is */ - return msm_pinmux_set_mux(pctldev, g->funcs[0], offset); + return msm_pinmux_set_mux(pctldev, + g->funcs[pctrl->soc->gpio_func], offset); } static const struct pinmux_ops msm_pinmux_ops = { diff --git a/drivers/pinctrl/qcom/pinctrl-msm.h b/drivers/pinctrl/qcom/pinctrl-msm.h index 333f99243c43..e31a5167c91e 100644 --- a/drivers/pinctrl/qcom/pinctrl-msm.h +++ b/drivers/pinctrl/qcom/pinctrl-msm.h @@ -118,6 +118,7 @@ struct msm_gpio_wakeirq_map { * @wakeirq_dual_edge_errata: If true then GPIOs using the wakeirq_map need * to be aware that their parent can't handle dual * edge interrupts. + * @gpio_func: Which function number is GPIO (usually 0). */ struct msm_pinctrl_soc_data { const struct pinctrl_pin_desc *pins; @@ -134,6 +135,7 @@ struct msm_pinctrl_soc_data { const struct msm_gpio_wakeirq_map *wakeirq_map; unsigned int nwakeirq_map; bool wakeirq_dual_edge_errata; + unsigned int gpio_func; }; extern const struct dev_pm_ops msm_pinctrl_dev_pm_ops; -- 2.29.2.576.ga3fc446d84-goog ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v3 2/3] pinctrl: qcom: Allow SoCs to specify a GPIO function that's not 0 2020-12-10 0:41 ` [PATCH v3 2/3] pinctrl: qcom: Allow SoCs to specify a GPIO function that's not 0 Douglas Anderson @ 2020-12-10 21:06 ` Stephen Boyd 0 siblings, 0 replies; 7+ messages in thread From: Stephen Boyd @ 2020-12-10 21:06 UTC (permalink / raw) To: Douglas Anderson, Jason Cooper, Linus Walleij, Marc Zyngier, Thomas Gleixner Cc: linux-arm-msm, Bjorn Andersson, Srinivas Ramana, Maulik Shah, Neeraj Upadhyay, Rajendra Nayak, linux-gpio, Douglas Anderson, Andy Gross, linux-kernel Quoting Douglas Anderson (2020-12-09 16:41:02) > There's currently a comment in the code saying function 0 is GPIO. > Instead of hardcoding it, let's add a member where an SoC can specify > it. No known SoCs use a number other than 0, but this just makes the > code clearer. NOTE: no SoC code needs to be updated since we can rely > on zero-initialization. > > Signed-off-by: Douglas Anderson <dianders@chromium.org> > --- Reviewed-by: Stephen Boyd <swboyd@chromium.org> ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v3 3/3] pinctrl: qcom: Clear possible pending irq when remuxing GPIOs 2020-12-10 0:41 [PATCH v3 1/3] irqchip: qcom-pdc: Fix phantom irq when changing between rising/falling Douglas Anderson 2020-12-10 0:41 ` [PATCH v3 2/3] pinctrl: qcom: Allow SoCs to specify a GPIO function that's not 0 Douglas Anderson @ 2020-12-10 0:41 ` Douglas Anderson 2020-12-10 21:56 ` Stephen Boyd 2020-12-10 21:11 ` [PATCH v3 1/3] irqchip: qcom-pdc: Fix phantom irq when changing between rising/falling Stephen Boyd 2 siblings, 1 reply; 7+ messages in thread From: Douglas Anderson @ 2020-12-10 0:41 UTC (permalink / raw) To: Marc Zyngier, Thomas Gleixner, Jason Cooper, Linus Walleij Cc: linux-arm-msm, Bjorn Andersson, Srinivas Ramana, Maulik Shah, Stephen Boyd, Neeraj Upadhyay, Rajendra Nayak, linux-gpio, Douglas Anderson, Andy Gross, linux-kernel Conceptually, we can envision the input on Qualcomm SoCs to pass through a bunch of blocks between coming into the chip and becoming a GPIO interrupt. From guessing and running a handful of tests, I believe that we can represent the state of the world with a drawing that looks something like this: +-----------------+ +-----------------+ +-----------------+ | INPUT | --> | PINMUX | | IS_INPUT | +-----------------+ | | --> | | | output bogus (?)| | output bogus (?)| | if not muxed | | if input disab. | +-----------------+ +-----------------+ | +---------------------------------------------------+--> to PDC | V +-----------------+ +-----------------+ +-----------------+ | INTR RAW ENABLE | | DETECTION LOGIC | | STATUS REGISTER | | | | | | | | output bogus (?)| --> | maybe handles | | latches inputs | | if disabled | | polarity diffs | --> | that are high | +-----------------+ | | | | | maybe debounces | | write 1 to clr | | level irqs | +-----------------+ +-----------------+ | | +---------------------------------------------------+ | V +-----------------+ | ENABLE | | | +-----------------+ | nothing passes | --> | SUMMARY IRQ | | through if | +-----------------+ | disabled | +-----------------+ The above might not be 100% exact, but for the purpose of this discussion, the point is that there are a whole bunch of gates and transformations on the input before it gets to the circuitry that generates interrupts. As you might guess, if you reconfigure one of the gates in the above diagram while the system is configured to detect interrupts things get a little wacky. Specifically it appears that if you gate the input at any step it can cause various glitches in the later steps because they are still paying attention to their input but their input isn't really sane anymore. I did some poking and I found that I could generate bogus interrupts in the system both when muxing away from GPIO mode and also when muxing back to GPIO mode. When configured to use the PDC path for generating interrupts I found that if the external input on the GPIO was low that I'd get what looked like a rising edge when unmuxing and a falling edge when muxing. When configured away from the PDC path I got slightly different glitch interrupts when changing muxing. These glitches when remuxing matter in reality, not just in theory. To be concrete, let's take the special "wakeup_irq" in qcom_geni_serial.c as an example. In sc7180-trogdor.dtsi we configure the uart3 to have two pinctrl states, sleep and default, and mux between the two during runtime PM and system suspend (see geni_se_resources_{on,off}() for more details). The difference between the sleep and default state is that the RX pin is muxed to a GPIO during sleep and muxed to the UART otherwise. When we switch between these two states we can generate the glitches talked about above because we're configured to look for edges but the transition from the gated input (which is bogus) to the real input can look like an edge. Historically the UART case above was handled by the fact that the "enable" function in the MSM GPIO driver did an "unmask and clear". This relied on the fact that the system happens to have the interrupt disabled until suspend time and that it would enable it after the pinmux change happened, thus clearing the interrupt. The historical solution, however, had a few problems. The first problem (that nobody seemed to have tripped) is that we can still get bogus interrupts if we remux when the interrupt isn't disabled during the muxing and re-enabled after. The second problem is that it violates how I believe that the interrupt enable path is supposed to work. In Linux, if a driver does disable_irq() and later does enable_irq() on its interrupt, I believe it's expecting these properties: * If an interrupt was pending when the driver disabled then it will still be pending after the driver re-enables. * If an edge-triggered interrupt comes in while an interrupt is disabled it should assert when the interrupt is re-enabled. If you think that the above sounds a lot like the disable_irq() and enable_irq() are supposed to be masking/unmasking the interrupt instead of disabling/enabling it then you've made an astute observation. Specifically when talking about interrupts, "mask" usually means to stop posting interrupts but keep tracking them and "disable" means to fully shut off interrupt detection. It's unfortunate that this is so confusing, but presumably this is all the way it is for historical reasons. Perhaps more confusing than the above is that, even though clients of IRQs themselves don't have a way to request mask/unmask vs. disable/enable calls, IRQ chips themselves can implement both. ...and yet more confusing is that if an IRQ chip implements disable/enable then they will be called when a client driver calls disable_irq() / enable_irq(). It does feel like some of the above could be cleared up. However, without any other core interrupt changes it should be clear that when an IRQ chip gets a request to "disable" an IRQ that it has to treat it like a mask of that IRQ. In any case, after that long interlude you can see that the "unmask and clear" can break things. Maulik tried to fix it so that we no longer did "unmask and clear" in commit 71266d9d3936 ("pinctrl: qcom: Move clearing pending IRQ to .irq_request_resources callback"), but it didn't work for two reasons: * It only tried to address the problem for interrupts that had parents (like the PDC). * It regressed the problem that the original clearing was trying to solve. I think we can safely assume that if someone muxes a pin to be something other than a GPIO and then muxes it back that we can clear any interrupts that were pending on it without violating any assumptions that client drivers are making. Presumably the client drivers are intentionally remuxing the pin away from a dedicated purpose to be a plain GPIO so they don't care what the pin state was before the mux switch and they don't expect to see the pin change level during this switch. Let's move the clearing of the IRQ to the pin muxing routine so that we'll clear a pending IRQ if we're muxing from some non-GPIO mode to a GPIO mode. NOTE: now that we're not clearing the interrupt in "enable" we also need one extra fix here to clear the phantom interrupt that could have been generated the first time we set RAW_STATUS_EN. Fixes: 71266d9d3936 ("pinctrl: qcom: Move clearing pending IRQ to .irq_request_resources callback") Signed-off-by: Douglas Anderson <dianders@chromium.org> --- This patch depends on #2 in the series, but not #1. #1 can land on its own and then #2/#3 can land together even without #1. The only reason patch #1 and #2/#3 are together in one series is because they address similar issues. I have done most of this patch testing on the Chrome OS 5.4 kernel tree (with many backports) but have sanity checked it on mainline. NOTE: there was quite a bit of discussion on v2 and I'm not sure I ever arrived on the same page as Maulik on how things here work. If there are truly problems with v3 I'd love to see some test code proving it out. Changes in v3: - Fixed bug in msm_gpio_direction_output() (s/oldval =/oldval = val =/) - Add back "if !skip_wake_irqs" test in msm_gpio_irq_enable() - For non-PDC, clear 1st interrupt in msm_gpio_irq_set_type() Changes in v2: - 0 => false - If skip_wake_irqs, don't need to clear normal intr. - Add comment about glitches in both output and input. drivers/pinctrl/qcom/pinctrl-msm.c | 122 ++++++++++++++++++++--------- 1 file changed, 86 insertions(+), 36 deletions(-) diff --git a/drivers/pinctrl/qcom/pinctrl-msm.c b/drivers/pinctrl/qcom/pinctrl-msm.c index 588df91274e2..915b1e2ad40d 100644 --- a/drivers/pinctrl/qcom/pinctrl-msm.c +++ b/drivers/pinctrl/qcom/pinctrl-msm.c @@ -166,14 +166,44 @@ static int msm_get_function_groups(struct pinctrl_dev *pctldev, return 0; } +static void msm_pinctrl_clear_pending_irq(struct msm_pinctrl *pctrl, + unsigned int group, + unsigned int irq) +{ + struct irq_data *d = irq_get_irq_data(irq); + const struct msm_pingroup *g; + unsigned long flags; + u32 val; + + if (!d) + return; + + if (d->parent_data && test_bit(d->hwirq, pctrl->skip_wake_irqs)) { + irq_chip_set_parent_state(d, IRQCHIP_STATE_PENDING, false); + return; + } + + g = &pctrl->soc->groups[group]; + + raw_spin_lock_irqsave(&pctrl->lock, flags); + val = msm_readl_intr_status(pctrl, g); + val &= ~BIT(g->intr_status_bit); + msm_writel_intr_status(val, pctrl, g); + raw_spin_unlock_irqrestore(&pctrl->lock, flags); +} + static int msm_pinmux_set_mux(struct pinctrl_dev *pctldev, unsigned function, unsigned group) { struct msm_pinctrl *pctrl = pinctrl_dev_get_drvdata(pctldev); + struct gpio_chip *gc = &pctrl->chip; + unsigned int irq = irq_find_mapping(gc->irq.domain, group); const struct msm_pingroup *g; unsigned long flags; u32 val, mask; + u32 oldval; + u32 old_i; int i; g = &pctrl->soc->groups[group]; @@ -187,15 +217,26 @@ static int msm_pinmux_set_mux(struct pinctrl_dev *pctldev, if (WARN_ON(i == g->nfuncs)) return -EINVAL; - raw_spin_lock_irqsave(&pctrl->lock, flags); + disable_irq(irq); - val = msm_readl_ctl(pctrl, g); + raw_spin_lock_irqsave(&pctrl->lock, flags); + oldval = val = msm_readl_ctl(pctrl, g); val &= ~mask; val |= i << g->mux_bit; msm_writel_ctl(val, pctrl, g); - raw_spin_unlock_irqrestore(&pctrl->lock, flags); + /* + * Clear IRQs if switching to/from GPIO mode since muxing to/from + * the GPIO path can cause phantom edges. + */ + old_i = (oldval & mask) >> g->mux_bit; + if (old_i != i && + (i == pctrl->soc->gpio_func || old_i == pctrl->soc->gpio_func)) + msm_pinctrl_clear_pending_irq(pctrl, group, irq); + + enable_irq(irq); + return 0; } @@ -456,32 +497,49 @@ static const struct pinconf_ops msm_pinconf_ops = { static int msm_gpio_direction_input(struct gpio_chip *chip, unsigned offset) { const struct msm_pingroup *g; + unsigned int irq = irq_find_mapping(chip->irq.domain, offset); struct msm_pinctrl *pctrl = gpiochip_get_data(chip); unsigned long flags; + u32 oldval; u32 val; g = &pctrl->soc->groups[offset]; + disable_irq(irq); + raw_spin_lock_irqsave(&pctrl->lock, flags); - val = msm_readl_ctl(pctrl, g); + oldval = val = msm_readl_ctl(pctrl, g); val &= ~BIT(g->oe_bit); msm_writel_ctl(val, pctrl, g); raw_spin_unlock_irqrestore(&pctrl->lock, flags); + /* + * Clear IRQs if switching to/from input mode since that can use + * a phantom edge. + */ + if (oldval != val) + msm_pinctrl_clear_pending_irq(pctrl, offset, irq); + + enable_irq(irq); + return 0; } static int msm_gpio_direction_output(struct gpio_chip *chip, unsigned offset, int value) { const struct msm_pingroup *g; + unsigned int irq = irq_find_mapping(chip->irq.domain, offset); struct msm_pinctrl *pctrl = gpiochip_get_data(chip); unsigned long flags; + u32 oldval; u32 val; g = &pctrl->soc->groups[offset]; + disable_irq(irq); + raw_spin_lock_irqsave(&pctrl->lock, flags); val = msm_readl_io(pctrl, g); @@ -491,12 +549,21 @@ static int msm_gpio_direction_output(struct gpio_chip *chip, unsigned offset, in val &= ~BIT(g->out_bit); msm_writel_io(val, pctrl, g); - val = msm_readl_ctl(pctrl, g); + oldval = val = msm_readl_ctl(pctrl, g); val |= BIT(g->oe_bit); msm_writel_ctl(val, pctrl, g); raw_spin_unlock_irqrestore(&pctrl->lock, flags); + /* + * Clear IRQs if switching to/from input mode since that can use + * a phantom edge. + */ + if (oldval != val) + msm_pinctrl_clear_pending_irq(pctrl, offset, irq); + + enable_irq(irq); + return 0; } @@ -774,7 +841,7 @@ static void msm_gpio_irq_mask(struct irq_data *d) raw_spin_unlock_irqrestore(&pctrl->lock, flags); } -static void msm_gpio_irq_clear_unmask(struct irq_data *d, bool status_clear) +static void msm_gpio_irq_unmask(struct irq_data *d) { struct gpio_chip *gc = irq_data_get_irq_chip_data(d); struct msm_pinctrl *pctrl = gpiochip_get_data(gc); @@ -792,17 +859,6 @@ static void msm_gpio_irq_clear_unmask(struct irq_data *d, bool status_clear) raw_spin_lock_irqsave(&pctrl->lock, flags); - if (status_clear) { - /* - * clear the interrupt status bit before unmask to avoid - * any erroneous interrupts that would have got latched - * when the interrupt is not in use. - */ - val = msm_readl_intr_status(pctrl, g); - val &= ~BIT(g->intr_status_bit); - msm_writel_intr_status(val, pctrl, g); - } - val = msm_readl_intr_cfg(pctrl, g); val |= BIT(g->intr_raw_status_bit); val |= BIT(g->intr_enable_bit); @@ -822,7 +878,7 @@ static void msm_gpio_irq_enable(struct irq_data *d) irq_chip_enable_parent(d); if (!test_bit(d->hwirq, pctrl->skip_wake_irqs)) - msm_gpio_irq_clear_unmask(d, true); + msm_gpio_irq_unmask(d); } static void msm_gpio_irq_disable(struct irq_data *d) @@ -837,11 +893,6 @@ static void msm_gpio_irq_disable(struct irq_data *d) msm_gpio_irq_mask(d); } -static void msm_gpio_irq_unmask(struct irq_data *d) -{ - msm_gpio_irq_clear_unmask(d, false); -} - /** * msm_gpio_update_dual_edge_parent() - Prime next edge for IRQs handled by parent. * @d: The irq dta. @@ -936,6 +987,7 @@ static int msm_gpio_irq_set_type(struct irq_data *d, unsigned int type) struct msm_pinctrl *pctrl = gpiochip_get_data(gc); const struct msm_pingroup *g; unsigned long flags; + bool was_enabled; u32 val; if (msm_gpio_needs_dual_edge_parent_workaround(d, type)) { @@ -997,6 +1049,7 @@ static int msm_gpio_irq_set_type(struct irq_data *d, unsigned int type) * could cause the INTR_STATUS to be set for EDGE interrupts. */ val = msm_readl_intr_cfg(pctrl, g); + was_enabled = val & BIT(g->intr_raw_status_bit); val |= BIT(g->intr_raw_status_bit); if (g->intr_detection_width == 2) { val &= ~(3 << g->intr_detection_bit); @@ -1046,6 +1099,16 @@ static int msm_gpio_irq_set_type(struct irq_data *d, unsigned int type) } msm_writel_intr_cfg(val, pctrl, g); + /* + * The first time we set RAW_STATUS_EN it could trigger an interrupt. + * Clear it. This is safe because we have IRQCHIP_SET_TYPE_MASKED. + */ + if (!was_enabled) { + val = msm_readl_intr_status(pctrl, g); + val &= ~BIT(g->intr_status_bit); + msm_writel_intr_status(val, pctrl, g); + } + if (test_bit(d->hwirq, pctrl->dual_edge_irqs)) msm_gpio_update_dual_edge_pos(pctrl, g, d); @@ -1097,19 +1160,6 @@ static int msm_gpio_irq_reqres(struct irq_data *d) ret = -EINVAL; goto out; } - - /* - * Clear the interrupt that may be pending before we enable - * the line. - * This is especially a problem with the GPIOs routed to the - * PDC. These GPIOs are direct-connect interrupts to the GIC. - * Disabling the interrupt line at the PDC does not prevent - * the interrupt from being latched at the GIC. The state at - * GIC needs to be cleared before enabling. - */ - if (d->parent_data && test_bit(d->hwirq, pctrl->skip_wake_irqs)) - irq_chip_set_parent_state(d, IRQCHIP_STATE_PENDING, 0); - return 0; out: module_put(gc->owner); -- 2.29.2.576.ga3fc446d84-goog ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v3 3/3] pinctrl: qcom: Clear possible pending irq when remuxing GPIOs 2020-12-10 0:41 ` [PATCH v3 3/3] pinctrl: qcom: Clear possible pending irq when remuxing GPIOs Douglas Anderson @ 2020-12-10 21:56 ` Stephen Boyd 2020-12-11 22:14 ` Doug Anderson 0 siblings, 1 reply; 7+ messages in thread From: Stephen Boyd @ 2020-12-10 21:56 UTC (permalink / raw) To: Douglas Anderson, Jason Cooper, Linus Walleij, Marc Zyngier, Thomas Gleixner Cc: linux-arm-msm, Bjorn Andersson, Srinivas Ramana, Maulik Shah, Neeraj Upadhyay, Rajendra Nayak, linux-gpio, Douglas Anderson, Andy Gross, linux-kernel Quoting Douglas Anderson (2020-12-09 16:41:03) > Conceptually, we can envision the input on Qualcomm SoCs to pass > through a bunch of blocks between coming into the chip and becoming a > GPIO interrupt. From guessing and running a handful of tests, I > believe that we can represent the state of the world with a drawing > that looks something like this: > > +-----------------+ +-----------------+ +-----------------+ > | INPUT | --> | PINMUX | | IS_INPUT | > +-----------------+ | | --> | | > | output bogus (?)| | output bogus (?)| > | if not muxed | | if input disab. | > +-----------------+ +-----------------+ > | > +---------------------------------------------------+--> to PDC > | > V > +-----------------+ +-----------------+ +-----------------+ > | INTR RAW ENABLE | | DETECTION LOGIC | | STATUS REGISTER | > | | | | | | > | output bogus (?)| --> | maybe handles | | latches inputs | > | if disabled | | polarity diffs | --> | that are high | > +-----------------+ | | | | > | maybe debounces | | write 1 to clr | > | level irqs | +-----------------+ > +-----------------+ | > | > +---------------------------------------------------+ > | > V > +-----------------+ > | ENABLE | > | | +-----------------+ > | nothing passes | --> | SUMMARY IRQ | > | through if | +-----------------+ > | disabled | > +-----------------+ This diagram doesn't make sense to me. The TLMM hardware block has a "summary IRQ" and then it also has a bunch of direct connections to the GIC via dedicated GIC SPI lines that are monitored by the PDC for wakeup purposes. I think the summary IRQ line (which is yet another GIC SPI line) is only in the picture when the GPIO isn't wakeup capable. So is that "to PDC" part of the diagram above indicating where the line goes off to the PDC and the GIC SPI line for each GPIO that is wakeup capable? From looking at the code it seems like the interrupt logic inside TLMM isn't used in the direct connect mode. It seems like the only way to ignore the GPIO at the GIC when it is directly connected is to fully shut it off at the GIC. Is that possible? Or that can't fix this because of below... > > The above might not be 100% exact, but for the purpose of this > discussion, the point is that there are a whole bunch of gates and > transformations on the input before it gets to the circuitry that > generates interrupts. Fair enough. I would like to know if any of the interrupt detection circuity is enabled/used in the parent PDC case vs. the summary irq line though. Presumably in the PDC case there is one or two gates, i.e. the input enable bit and the pinmux function selection vs. the summary irq line that has those two gates plus the raw status and non-raw status enable bits. > > As you might guess, if you reconfigure one of the gates in the above > diagram while the system is configured to detect interrupts things get > a little wacky. Specifically it appears that if you gate the input at > any step it can cause various glitches in the later steps because they > are still paying attention to their input but their input isn't really > sane anymore. > > I did some poking and I found that I could generate bogus interrupts > in the system both when muxing away from GPIO mode and also when > muxing back to GPIO mode. When configured to use the PDC path for > generating interrupts I found that if the external input on the GPIO > was low that I'd get what looked like a rising edge when unmuxing and > a falling edge when muxing. When configured away from the PDC path I > got slightly different glitch interrupts when changing muxing. Continued from above, just changing the mode from GPIO to some other mode like UART seems to cause the GIC to notice an edge? So the other gates that come after have been tested and cause problems too? Or is it just the mode change that causes a problem? Is there any way to tell TLMM that "no I don't want to use the direct connect path, I want to use the summary irq path"? > > These glitches when remuxing matter in reality, not just in theory. > To be concrete, let's take the special "wakeup_irq" in > qcom_geni_serial.c as an example. In sc7180-trogdor.dtsi we configure > the uart3 to have two pinctrl states, sleep and default, and mux > between the two during runtime PM and system suspend (see > geni_se_resources_{on,off}() for more details). The difference > between the sleep and default state is that the RX pin is muxed to a > GPIO during sleep and muxed to the UART otherwise. When we switch > between these two states we can generate the glitches talked about > above because we're configured to look for edges but the transition > from the gated input (which is bogus) to the real input can look like > an edge. > > Historically the UART case above was handled by the fact that the > "enable" function in the MSM GPIO driver did an "unmask and clear". > This relied on the fact that the system happens to have the interrupt > disabled until suspend time and that it would enable it after the > pinmux change happened, thus clearing the interrupt. > > The historical solution, however, had a few problems. The first > problem (that nobody seemed to have tripped) is that we can still get > bogus interrupts if we remux when the interrupt isn't disabled during > the muxing and re-enabled after. The second problem is that it > violates how I believe that the interrupt enable path is supposed to > work. > > In Linux, if a driver does disable_irq() and later does enable_irq() > on its interrupt, I believe it's expecting these properties: > * If an interrupt was pending when the driver disabled then it will > still be pending after the driver re-enables. > * If an edge-triggered interrupt comes in while an interrupt is > disabled it should assert when the interrupt is re-enabled. > > If you think that the above sounds a lot like the disable_irq() and > enable_irq() are supposed to be masking/unmasking the interrupt > instead of disabling/enabling it then you've made an astute > observation. Specifically when talking about interrupts, "mask" > usually means to stop posting interrupts but keep tracking them and > "disable" means to fully shut off interrupt detection. It's > unfortunate that this is so confusing, but presumably this is all the > way it is for historical reasons. > > Perhaps more confusing than the above is that, even though clients of > IRQs themselves don't have a way to request mask/unmask > vs. disable/enable calls, IRQ chips themselves can implement both. > ...and yet more confusing is that if an IRQ chip implements > disable/enable then they will be called when a client driver calls > disable_irq() / enable_irq(). > > It does feel like some of the above could be cleared up. However, > without any other core interrupt changes it should be clear that when > an IRQ chip gets a request to "disable" an IRQ that it has to treat it > like a mask of that IRQ. > > In any case, after that long interlude you can see that the "unmask > and clear" can break things. Maulik tried to fix it so that we no > longer did "unmask and clear" in commit 71266d9d3936 ("pinctrl: qcom: > Move clearing pending IRQ to .irq_request_resources callback"), but it > didn't work for two reasons: > * It only tried to address the problem for interrupts that had parents > (like the PDC). > * It regressed the problem that the original clearing was trying to > solve. > > I think we can safely assume that if someone muxes a pin to be > something other than a GPIO and then muxes it back that we can clear > any interrupts that were pending on it without violating any > assumptions that client drivers are making. Presumably the client > drivers are intentionally remuxing the pin away from a dedicated > purpose to be a plain GPIO so they don't care what the pin state was > before the mux switch and they don't expect to see the pin change > level during this switch. Let's move the clearing of the IRQ to the > pin muxing routine so that we'll clear a pending IRQ if we're muxing > from some non-GPIO mode to a GPIO mode. > > NOTE: now that we're not clearing the interrupt in "enable" we also > need one extra fix here to clear the phantom interrupt that could have > been generated the first time we set RAW_STATUS_EN. > > Fixes: 71266d9d3936 ("pinctrl: qcom: Move clearing pending IRQ to .irq_request_resources callback") > Signed-off-by: Douglas Anderson <dianders@chromium.org> > --- Would it be possible to split this patch in two to handle the case where there is a parent and the case where there isn't a parent? Has the manual testing probed both paths, or only one path like the PDC path or the summary irq path? > This patch depends on #2 in the series, but not #1. #1 can land on > its own and then #2/#3 can land together even without #1. The only > reason patch #1 and #2/#3 are together in one series is because they > address similar issues. > > I have done most of this patch testing on the Chrome OS 5.4 kernel > tree (with many backports) but have sanity checked it on mainline. > > NOTE: there was quite a bit of discussion on v2 and I'm not sure I > ever arrived on the same page as Maulik on how things here work. If > there are truly problems with v3 I'd love to see some test code > proving it out. > > Changes in v3: > - Fixed bug in msm_gpio_direction_output() (s/oldval =/oldval = val =/) > - Add back "if !skip_wake_irqs" test in msm_gpio_irq_enable() > - For non-PDC, clear 1st interrupt in msm_gpio_irq_set_type() > > Changes in v2: > - 0 => false > - If skip_wake_irqs, don't need to clear normal intr. > - Add comment about glitches in both output and input. > > drivers/pinctrl/qcom/pinctrl-msm.c | 122 ++++++++++++++++++++--------- > 1 file changed, 86 insertions(+), 36 deletions(-) > > diff --git a/drivers/pinctrl/qcom/pinctrl-msm.c b/drivers/pinctrl/qcom/pinctrl-msm.c > index 588df91274e2..915b1e2ad40d 100644 > --- a/drivers/pinctrl/qcom/pinctrl-msm.c > +++ b/drivers/pinctrl/qcom/pinctrl-msm.c > @@ -491,12 +549,21 @@ static int msm_gpio_direction_output(struct gpio_chip *chip, unsigned offset, in > val &= ~BIT(g->out_bit); > msm_writel_io(val, pctrl, g); > > - val = msm_readl_ctl(pctrl, g); > + oldval = val = msm_readl_ctl(pctrl, g); > val |= BIT(g->oe_bit); > msm_writel_ctl(val, pctrl, g); > > raw_spin_unlock_irqrestore(&pctrl->lock, flags); > > + /* > + * Clear IRQs if switching to/from input mode since that can use > + * a phantom edge. > + */ > + if (oldval != val) > + msm_pinctrl_clear_pending_irq(pctrl, offset, irq); > + > + enable_irq(irq); This stuff where we call enable_irq() and disable_irq() makes me nervous. No other pinctrl driver is doing that. > + > return 0; > } > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v3 3/3] pinctrl: qcom: Clear possible pending irq when remuxing GPIOs 2020-12-10 21:56 ` Stephen Boyd @ 2020-12-11 22:14 ` Doug Anderson 0 siblings, 0 replies; 7+ messages in thread From: Doug Anderson @ 2020-12-11 22:14 UTC (permalink / raw) To: Stephen Boyd Cc: Jason Cooper, Linus Walleij, Marc Zyngier, Thomas Gleixner, linux-arm-msm, Bjorn Andersson, Srinivas Ramana, Maulik Shah, Neeraj Upadhyay, Rajendra Nayak, open list:GPIO SUBSYSTEM, Andy Gross, LKML Hi, On Thu, Dec 10, 2020 at 1:56 PM Stephen Boyd <swboyd@chromium.org> wrote: > > Quoting Douglas Anderson (2020-12-09 16:41:03) > > Conceptually, we can envision the input on Qualcomm SoCs to pass > > through a bunch of blocks between coming into the chip and becoming a > > GPIO interrupt. From guessing and running a handful of tests, I > > believe that we can represent the state of the world with a drawing > > that looks something like this: > > > > +-----------------+ +-----------------+ +-----------------+ > > | INPUT | --> | PINMUX | | IS_INPUT | > > +-----------------+ | | --> | | > > | output bogus (?)| | output bogus (?)| > > | if not muxed | | if input disab. | > > +-----------------+ +-----------------+ > > | > > +---------------------------------------------------+--> to PDC > > | > > V > > +-----------------+ +-----------------+ +-----------------+ > > | INTR RAW ENABLE | | DETECTION LOGIC | | STATUS REGISTER | > > | | | | | | > > | output bogus (?)| --> | maybe handles | | latches inputs | > > | if disabled | | polarity diffs | --> | that are high | > > +-----------------+ | | | | > > | maybe debounces | | write 1 to clr | > > | level irqs | +-----------------+ > > +-----------------+ | > > | > > +---------------------------------------------------+ > > | > > V > > +-----------------+ > > | ENABLE | > > | | +-----------------+ > > | nothing passes | --> | SUMMARY IRQ | > > | through if | +-----------------+ > > | disabled | > > +-----------------+ > > This diagram doesn't make sense to me. I've gutted most of this code for v4 after Maulik pointed out why my testing was flawed. Hopefully v4 looks saner... -Doug ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v3 1/3] irqchip: qcom-pdc: Fix phantom irq when changing between rising/falling 2020-12-10 0:41 [PATCH v3 1/3] irqchip: qcom-pdc: Fix phantom irq when changing between rising/falling Douglas Anderson 2020-12-10 0:41 ` [PATCH v3 2/3] pinctrl: qcom: Allow SoCs to specify a GPIO function that's not 0 Douglas Anderson 2020-12-10 0:41 ` [PATCH v3 3/3] pinctrl: qcom: Clear possible pending irq when remuxing GPIOs Douglas Anderson @ 2020-12-10 21:11 ` Stephen Boyd 2 siblings, 0 replies; 7+ messages in thread From: Stephen Boyd @ 2020-12-10 21:11 UTC (permalink / raw) To: Douglas Anderson, Jason Cooper, Linus Walleij, Marc Zyngier, Thomas Gleixner Cc: linux-arm-msm, Bjorn Andersson, Srinivas Ramana, Maulik Shah, Neeraj Upadhyay, Rajendra Nayak, linux-gpio, Douglas Anderson, Andy Gross, Archana Sathyakumar, Lina Iyer, linux-kernel Quoting Douglas Anderson (2020-12-09 16:41:01) > We have a problem if we use gpio-keys and configure wakeups such that > we only want one edge to wake us up. AKA: > wakeup-event-action = <EV_ACT_DEASSERTED>; > wakeup-source; > > Specifically we end up with a phantom interrupt that blocks suspend if > the line was already high and we want wakeups on rising edges (AKA we > want the GPIO to go low and then high again before we wake up). The > opposite is also problematic. > > Specifically, here's what's happening today: > 1. Normally, gpio-keys configures to look for both edges. Due to the > current workaround introduced in commit c3c0c2e18d94 ("pinctrl: > qcom: Handle broken/missing PDC dual edge IRQs on sc7180"), if the > line was high we'd configure for falling edges. > 2. At suspend time, we change to look for rising edges. > 3. After qcom_pdc_gic_set_type() runs, we get a phantom interrupt. > > We can solve this by just clearing the phantom interrupt. > > NOTE: it is possible that this could cause problems for a client with > very specific needs, but there's not much we can do with this > hardware. As an example, let's say the interrupt signal is currently > high and the client is looking for falling edges. The client now > changes to look for rising edges. The client could possibly expect > that if the line has a short pulse low (and back high) that it would > always be detected. Specifically no matter when the pulse happened, > it should either have tripped the (old) falling edge trigger or the > (new) rising edge trigger. We will simply not trip it. We could > narrow down the race a bit by polling our parent before changing > types, but no matter what we do there will still be a period of time > where we can't tell the difference between a real transition (or more > than one transition) and the phantom. > > Fixes: f55c73aef890 ("irqchip/pdc: Add PDC interrupt controller for QCOM SoCs") > Signed-off-by: Douglas Anderson <dianders@chromium.org> > Reviewed-by: Maulik Shah <mkshah@codeaurora.org> > Tested-by: Maulik Shah <mkshah@codeaurora.org> > --- Reviewed-by: Stephen Boyd <swboyd@chromium.org> ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2020-12-11 23:10 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-12-10 0:41 [PATCH v3 1/3] irqchip: qcom-pdc: Fix phantom irq when changing between rising/falling Douglas Anderson 2020-12-10 0:41 ` [PATCH v3 2/3] pinctrl: qcom: Allow SoCs to specify a GPIO function that's not 0 Douglas Anderson 2020-12-10 21:06 ` Stephen Boyd 2020-12-10 0:41 ` [PATCH v3 3/3] pinctrl: qcom: Clear possible pending irq when remuxing GPIOs Douglas Anderson 2020-12-10 21:56 ` Stephen Boyd 2020-12-11 22:14 ` Doug Anderson 2020-12-10 21:11 ` [PATCH v3 1/3] irqchip: qcom-pdc: Fix phantom irq when changing between rising/falling Stephen Boyd
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