| Message ID | 20240920100711.2744120-1-ruanjinjie@huawei.com |
|---|---|
| State | Accepted |
| Commit | d505d3593b52b6c43507f119572409087416ba28 |
| Headers | show |
| Series | net: wwan: qcom_bam_dmux: Fix missing pm_runtime_disable() | expand |
On 2024/9/20 21:38, Stephan Gerhold wrote: > On Fri, Sep 20, 2024 at 03:05:13PM +0200, Dmitry Baryshkov wrote: >> On Fri, 20 Sept 2024 at 14:44, Stephan Gerhold >> <stephan.gerhold@linaro.org> wrote: >>> >>> On Fri, Sep 20, 2024 at 01:48:15PM +0300, Dmitry Baryshkov wrote: >>>> On Fri, Sep 20, 2024 at 06:07:11PM GMT, Jinjie Ruan wrote: >>>>> It's important to undo pm_runtime_use_autosuspend() with >>>>> pm_runtime_dont_use_autosuspend() at driver exit time. >>>>> >>>>> But the pm_runtime_disable() and pm_runtime_dont_use_autosuspend() >>>>> is missing in the error path for bam_dmux_probe(). So add it. >>>> >>>> Please use devm_pm_runtime_enable(), which handles autosuspend. >>>> >>> >>> This would conflict with the existing cleanup in bam_dmux_remove(), >>> which probably needs to stay manually managed since the tear down order >>> is quite important there. >> >> Hmm, the setup and teardown code makes me wonder now. > > Yeah, you ask the right questions. :-) It's really tricky to get this > 100% right. I spent quite some time to get close, but there are likely > still some loopholes. I haven't heard of anyone running into trouble, > though. This driver has been rock solid for the past few years. > >> Are we guaranteed that the IRQs can not be delivered after suspending >> the device? > > I think bam_dmux_remove() should be safe. disable_irq(dmux->pc_irq) > prevents any further delivery of IRQs before doing the final power off. > >> Also is there a race between IRQs being enabled, manual check of the >> IRQ state and the pc_ack / power_off calls? > > Yes, I'm pretty sure this race exists in theory. I'm not sure how to > avoid it. We would need an atomic "return current state and enable IRQ" > operation, but I don't think this exists at the moment. Do you have any > suggestions? Maybe use IRQF_NO_AUTOEN flag to reuqest irq and enable_irq() after that? > > Thanks, > Stephan
On Mon, Sep 23, 2024 at 10:25:28AM +0800, Jinjie Ruan wrote: > > > On 2024/9/20 21:38, Stephan Gerhold wrote: > > On Fri, Sep 20, 2024 at 03:05:13PM +0200, Dmitry Baryshkov wrote: > >> On Fri, 20 Sept 2024 at 14:44, Stephan Gerhold > >> <stephan.gerhold@linaro.org> wrote: > >>> > >>> On Fri, Sep 20, 2024 at 01:48:15PM +0300, Dmitry Baryshkov wrote: > >>>> On Fri, Sep 20, 2024 at 06:07:11PM GMT, Jinjie Ruan wrote: > >>>>> It's important to undo pm_runtime_use_autosuspend() with > >>>>> pm_runtime_dont_use_autosuspend() at driver exit time. > >>>>> > >>>>> But the pm_runtime_disable() and pm_runtime_dont_use_autosuspend() > >>>>> is missing in the error path for bam_dmux_probe(). So add it. > >>>> > >>>> Please use devm_pm_runtime_enable(), which handles autosuspend. > >>>> > >>> > >>> This would conflict with the existing cleanup in bam_dmux_remove(), > >>> which probably needs to stay manually managed since the tear down order > >>> is quite important there. > >> > >> Hmm, the setup and teardown code makes me wonder now. > > > > Yeah, you ask the right questions. :-) It's really tricky to get this > > 100% right. I spent quite some time to get close, but there are likely > > still some loopholes. I haven't heard of anyone running into trouble, > > though. This driver has been rock solid for the past few years. > > > >> Are we guaranteed that the IRQs can not be delivered after suspending > >> the device? > > > > I think bam_dmux_remove() should be safe. disable_irq(dmux->pc_irq) > > prevents any further delivery of IRQs before doing the final power off. > > > >> Also is there a race between IRQs being enabled, manual check of the > >> IRQ state and the pc_ack / power_off calls? > > > > Yes, I'm pretty sure this race exists in theory. I'm not sure how to > > avoid it. We would need an atomic "return current state and enable IRQ" > > operation, but I don't think this exists at the moment. Do you have any > > suggestions? > > Maybe use IRQF_NO_AUTOEN flag to reuqest irq and enable_irq() after that? > I thought about that too, but I think that might introduce a small window in between the two calls where we would miss the state change: irq_get_irqchip_state(..., IRQCHIP_STATE_LINE_LEVEL, ...); /* if an interrupt arrives here we will miss the state change */ enable_irq(); Thanks, Stephan
On 2024/9/20 20:45, Stephan Gerhold wrote: > On Fri, Sep 20, 2024 at 06:07:11PM +0800, Jinjie Ruan wrote: >> It's important to undo pm_runtime_use_autosuspend() with >> pm_runtime_dont_use_autosuspend() at driver exit time. >> >> But the pm_runtime_disable() and pm_runtime_dont_use_autosuspend() >> is missing in the error path for bam_dmux_probe(). So add it. >> >> Fixes: 21a0ffd9b38c ("net: wwan: Add Qualcomm BAM-DMUX WWAN network driver") >> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com> >> --- >> drivers/net/wwan/qcom_bam_dmux.c | 12 +++++++++--- >> 1 file changed, 9 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/net/wwan/qcom_bam_dmux.c b/drivers/net/wwan/qcom_bam_dmux.c >> index 26ca719fa0de..34a4e8095161 100644 >> --- a/drivers/net/wwan/qcom_bam_dmux.c >> +++ b/drivers/net/wwan/qcom_bam_dmux.c >> @@ -823,17 +823,17 @@ static int bam_dmux_probe(struct platform_device *pdev) >> ret = devm_request_threaded_irq(dev, pc_ack_irq, NULL, bam_dmux_pc_ack_irq, >> IRQF_ONESHOT, NULL, dmux); >> if (ret) >> - return ret; >> + goto err_disable_pm; >> >> ret = devm_request_threaded_irq(dev, dmux->pc_irq, NULL, bam_dmux_pc_irq, >> IRQF_ONESHOT, NULL, dmux); >> if (ret) >> - return ret; >> + goto err_disable_pm; >> >> ret = irq_get_irqchip_state(dmux->pc_irq, IRQCHIP_STATE_LINE_LEVEL, >> &dmux->pc_state); >> if (ret) >> - return ret; >> + goto err_disable_pm; >> >> /* Check if remote finished initialization before us */ >> if (dmux->pc_state) { >> @@ -844,6 +844,12 @@ static int bam_dmux_probe(struct platform_device *pdev) >> } >> >> return 0; >> + >> +err_disable_pm: >> + pm_runtime_disable(dev); >> + pm_runtime_dont_use_autosuspend(dev); >> + pm_runtime_set_suspended(dev); > > Please drop the pm_runtime_set_suspended(dev); line, it should be > unneeded since runtime PM documentation says: > > the initial runtime PM status of all devices is ‘suspended’ Thank you! > > Thanks, > Stephan
diff --git a/drivers/net/wwan/qcom_bam_dmux.c b/drivers/net/wwan/qcom_bam_dmux.c index 26ca719fa0de..34a4e8095161 100644 --- a/drivers/net/wwan/qcom_bam_dmux.c +++ b/drivers/net/wwan/qcom_bam_dmux.c @@ -823,17 +823,17 @@ static int bam_dmux_probe(struct platform_device *pdev) ret = devm_request_threaded_irq(dev, pc_ack_irq, NULL, bam_dmux_pc_ack_irq, IRQF_ONESHOT, NULL, dmux); if (ret) - return ret; + goto err_disable_pm; ret = devm_request_threaded_irq(dev, dmux->pc_irq, NULL, bam_dmux_pc_irq, IRQF_ONESHOT, NULL, dmux); if (ret) - return ret; + goto err_disable_pm; ret = irq_get_irqchip_state(dmux->pc_irq, IRQCHIP_STATE_LINE_LEVEL, &dmux->pc_state); if (ret) - return ret; + goto err_disable_pm; /* Check if remote finished initialization before us */ if (dmux->pc_state) { @@ -844,6 +844,12 @@ static int bam_dmux_probe(struct platform_device *pdev) } return 0; + +err_disable_pm: + pm_runtime_disable(dev); + pm_runtime_dont_use_autosuspend(dev); + pm_runtime_set_suspended(dev); + return ret; } static void bam_dmux_remove(struct platform_device *pdev)
It's important to undo pm_runtime_use_autosuspend() with pm_runtime_dont_use_autosuspend() at driver exit time. But the pm_runtime_disable() and pm_runtime_dont_use_autosuspend() is missing in the error path for bam_dmux_probe(). So add it. Fixes: 21a0ffd9b38c ("net: wwan: Add Qualcomm BAM-DMUX WWAN network driver") Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com> --- drivers/net/wwan/qcom_bam_dmux.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)