On 12 June 2018 at 11:52, Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote: > Hi Ulf, > > On 2018-06-12 11:20, Ulf Hansson wrote: >> On 12 June 2018 at 10:28, Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote: >>> On 2018-06-11 14:24, Ulf Hansson wrote: >>>> On 11 June 2018 at 11:50, Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote: >>>>> On 2018-06-11 11:35, Ulf Hansson wrote: >>>>>> On 11 June 2018 at 08:48, Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote: >>>>>>> dw_mci_exynos_resume_noirq() performs DWMMC register access without >>>>>>> ensuring that respective clocks are enabled. This might cause external >>>>>>> abort on some systems (observed on Exynos5433 based boards). Fix this >>>>>>> by adding needed prepare_enable/disable_unprepare calls. >>>>>>> >>>>>>> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> >>>>>>> --- >>>>>>> drivers/mmc/host/dw_mmc-exynos.c | 6 ++++++ >>>>>>> 1 file changed, 6 insertions(+) >>>>>>> >>>>>>> diff --git a/drivers/mmc/host/dw_mmc-exynos.c b/drivers/mmc/host/dw_mmc-exynos.c >>>>>>> index 3164681108ae..6125b68726b0 100644 >>>>>>> --- a/drivers/mmc/host/dw_mmc-exynos.c >>>>>>> +++ b/drivers/mmc/host/dw_mmc-exynos.c >>>>>>> @@ -193,6 +193,9 @@ static int dw_mci_exynos_resume_noirq(struct device *dev) >>>>>>> struct dw_mci_exynos_priv_data *priv = host->priv; >>>>>>> u32 clksel; >>>>>>> >>>>>>> + clk_prepare_enable(host->biu_clk); >>>>>>> + clk_prepare_enable(host->ciu_clk); >>>>>>> + >>>>>>> if (priv->ctrl_type == DW_MCI_TYPE_EXYNOS7 || >>>>>>> priv->ctrl_type == DW_MCI_TYPE_EXYNOS7_SMU) >>>>>>> clksel = mci_readl(host, CLKSEL64); >>>>>>> @@ -207,6 +210,9 @@ static int dw_mci_exynos_resume_noirq(struct device *dev) >>>>>>> mci_writel(host, CLKSEL, clksel); >>>>>>> } >>>>>>> >>>>>>> + clk_disable_unprepare(host->biu_clk); >>>>>>> + clk_disable_unprepare(host->ciu_clk); >>>>>>> + >>>>>>> return 0; >>>>>>> } >>>>>>> #else >>>>>> I looked a little closer and I am wondering if it wouldn't be possible >>>>>> to use SET_NOIRQ_SYSTEM_SLEEP_PM_OPS() instead of >>>>>> SET_SYSTEM_SLEEP_PM_OPS()? >>>>>> >>>>>> Somelike this: >>>>>> SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, >>>>>> dw_mci_exynos_resume_noirq) >>>>>> >>>>>> Then from dw_mci_exynos_resume_noirq() call pm_runtime_force_resume(). >>>>>> >>>>>> I think it would simplify the code a bit, as you can rely on the >>>>>> runtime PM callbacks to deal with clk_prepare_enable() and >>>>>> clk_disable_unprepare(), unless I am mistaken. >>>>> This will not fix the problem, because mci_writel() calls in >>>>> dw_mci_exynos_resume_noirq are done unconditionally, regardless of the >>>>> controller's runtime pm state. Since commit 1d9174fbc55e after calling >>>>> pm_runtime_force_resume() there is no guarantee that device is in >>>>> runtime active state if it was runtime suspended state. >>>> Yes, because the runtime PM usage count is greater than 1. >>>> (pm_runtime_get_noresume() is called during probe). >>>> >>>> If you want to make this explicit (not relying on ->probe()), one can >>>> add a ->suspend_noirq() callback and call pm_runtime_get_noresume() in >>>> it. >>> Sorry, but I don't get how this would work. Exactly the same pattern as >>> you have proposed was already used in s3c-64xx SPI driver and it didn't >>> work properly (tested on the same SoC as this DW-MMC change). I had to >>> move register access to runtime resume callback to fix external abort >>> issue: >>> >>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e935dba111621bd6a0c5d48e6511a4d9885103b4 >> Yep, that is a correct solution. >> >>> Here in DW-MMC driver such approach (moving all the code to runtime >>> resume callback) is not possible because of the potential interrupt storm >>> caused by the hw bug (that's the reason of using noirq resume callback). >> I understand. What you need is to run the runtime resume/suspend >> callbacks in the resume/suspend noirq phase. Moreover, you need to >> make sure that the runtime resume callback, really becomes invoked >> during the resume noirq phase, because of the HW bug. >> >> I think the below should work. Can you give it a try? >> >> It relies on the call pm_runtime_get_noresume(), done during >> ->probe(). Note that, the driver always keeps the RPM usage count >> increased, thus preventing runtime suspend during normal execution. >> >> Anyway, if this doesn't work, your suggested approach works fine as well. > > Okay, finally I got it. I wasn't aware that dw_mmc-exynos keeps device > runtime active all the time between the driver probe() and remove(). > Right, this will fix this specific case, but it isn't a generic solution, > so I will also add a comment on that, so one would not need to debug it > again if he decides to change runtime pm usage scheme in dw_mmc-exynos > in the future. Seems reasonable! If you want the more generic solution, I would add a exynos specific suspend_noirq() callback, let it call pm_runtime_get_noresume() and them pm_runtime_force_suspend(). In the corresponding resume_noirq() callback, extend my suggested changes, with a call to pm_runtime_put_noidle() after all actions has been done in it. Kind regards Uffe -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
