Messages in this thread | | | Subject | Re: [PATCH] ata: ahci-platform: add reset control support | From | Hans de Goede <> | Date | Fri, 6 Apr 2018 12:12:11 +0200 |
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Hi,
On 06-04-18 11:36, Kunihiko Hayashi wrote: > Hi Hans, > > On Fri, 6 Apr 2018 10:29:37 +0200 > Hans de Goede <hdegoede@redhat.com> wrote: > >> Hi, >> >> On 06-04-18 06:48, Kunihiko Hayashi wrote: >>> Hi Hans, >>>> On Thu, 5 Apr 2018 16:08:24 +0200 >>> Hans de Goede <hdegoede@redhat.com> wrote: >>>>> Hi, >>>> >>>> On 05-04-18 16:00, Hans de Goede wrote: >>>>> Hi, >>>>>> On 05-04-18 15:54, Thierry Reding wrote: >>>>>> On Thu, Apr 05, 2018 at 03:27:03PM +0200, Hans de Goede wrote: >>>>>>> Hi, >>>>>>> >>>>>>> On 05-04-18 15:17, Patrice CHOTARD wrote: >>>>>>>> Hi Thierry >>>>>>>> >>>>>>>> On 04/05/2018 11:54 AM, Thierry Reding wrote: >>>>>>>>> On Fri, Mar 23, 2018 at 10:30:53AM +0900, Kunihiko Hayashi wrote: >>>>>>>>>> Add support to get and control a list of resets for the device >>>>>>>>>> as optional and shared. These resets must be kept de-asserted until >>>>>>>>>> the device is enabled. >>>>>>>>>> >>>>>>>>>> This is specified as shared because some SoCs like UniPhier series >>>>>>>>>> have common reset controls with all ahci controller instances. >>>>>>>>>> >>>>>>>>>> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com> >>>>>>>>>> --- >>>>>>>>>> ??? .../devicetree/bindings/ata/ahci-platform.txt????? |? 1 + >>>>>>>>>> ??? drivers/ata/ahci.h???????????????????????????????? |? 1 + >>>>>>>>>> ??? drivers/ata/libahci_platform.c???????????????????? | 24 +++++++++++++++++++--- >>>>>>>>>> ??? 3 files changed, 23 insertions(+), 3 deletions(-) >>>>>>>>> >>>>>>>>> This causes a regression on Tegra because we explicitly request the >>>>>>>>> resets after the call to ahci_platform_get_resources(). >>>>>>>> >>>>>>>> I confirm, we got exactly the same behavior on STi platform. >>>>>>>> >>>>>>>>> >>>>>>>>> ?? From a quick look, ahci_mtk and ahci_st are in the same boat, adding the >>>>>>>>> corresponding maintainers to Cc. >>>>>>>>> >>>>>>>>> Patrice, Matthias: does SATA still work for you after this patch? This >>>>>>>>> has been in linux-next since next-20180327. >>>>>>>> >>>>>>>> SATA is still working after this patch, but a kernel warning is >>>>>>>> triggered due to the fact that resets are both requested by >>>>>>>> libahci_platform and by ahci_st driver. >>>>>>> >>>>>>> So in your case you might be able to remove the reset handling >>>>>>> from the ahci_st driver and rely on the new libahci_platform >>>>>>> handling instead? If that works that seems like a win to me. >>>>>>> >>>>>>> As said elsewhere in this thread I think it makes sense to keep (or re-add >>>>>>> after a revert) the libahci_platform reset code, but make it conditional >>>>>>> on a flag passed to ahci_platform_get_resources(). This way we get >>>>>>> the shared code for most cases and platforms which need special handling >>>>>>> can opt-out. >>>>>> >>>>>> Agreed, although I prefer such helpers to be opt-in, rather than >>>>>> opt-out. In my experience that tends make the helpers more resilient to >>>>>> this kind of regression. It also simplifies things because instead of >>>>>> drivers saying "I want all the helpers except this one and that one", >>>>>> they can simply say "I want these helpers and that one". In the former >>>>>> case whenever you add some new (opt-out) feature, you have to update all >>>>>> drivers and add the exception. In the latter you only need to extend the >>>>>> drivers that want to make use of the new helper. >>>> >>>> Erm, the idea never was to make this opt-out but rather opt in, so >>>> we add a flags parameter to ahci_platform_get_resources() and all >>>> current users pass in 0 for that to keep the current behavior. >>>> >>>> And only the generic drivers/ata/ahci_platform.c driver will pass >>>> in a the new AHCI_PLATFORM_GET_RESETS flag, which makes >>>> ahci_platform_get_resources() (and the other functions) also deal >>>> with resets. >>>> >>>>>> With that in mind, rather than adding a flag to the >>>>>> ahci_platform_get_resources() function, it might be more flexible to >>>>>> split the helpers into finer-grained functions. That way drivers can >>>>>> pick whatever functionality they want from the helpers. >>>>>> Good point, so lets: >>>>>> 1) Revert the patch for now >>>>> 2) Have a new version of the patch which adds a ahci_platform_get_resets() helper >>>>> 3) Modify the generic drivers/ata/ahci_platform.c driver to call the new >>>>> ?? ahci_platform_get_resets() between its ahci_platform_get_resources() >>>>> ?? and ahci_platform_enable_resources() calls. >>>>> ?? I think that ahci_platform_enable_resources() should still automatically >>>>> ?? do the right thing wrt resets if ahci_platform_get_resets() was called >>>>> ?? (otherwise the resets array will be empty and should be skipped) >>>>>> This should make the generic driver usable for the UniPhier SoCs and >>>>> maybe some other drivers like the ahci_st driver can also switch to the >>>>> new ahci_platform_get_resets() functionality to reduce their code a bit. >>>> >>>> So thinking slightly longer about this, with the opt-in variant >>>> (which is what I intended all along) I do think that a flags parameter >>>> is better, because the whole idea behind lib_ahci_platform is to avoid >>>> having to do err = get_resource_a(), if (err) bail, err = get_resource_b() >>>> if (err) bail, etc. in all the ahci (platform) drivers. And having fine >>>> grained helpers re-introduces that. >>>> In case of adding a flag instead of get_resource_a(), >>> for example, we add the flag for use of resets, >>>> -struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev) >>> +struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev, >>> + bool use_reset) >>>> and for now all the drivers using this function need to add the argument as false >>> to the caller. >>>> - hpriv = ahci_platform_get_resources(pdev); >>> + hpriv = ahci_platform_get_resources(pdev, false); >>>> Surely this can avoid adding functions such get_resource_a(). If we apply another >>> feature later, we add its flag as one of the arguments instead. Is it right? >> >> Yes, that is right, but instead of adding a "bool use_reset" please add >> an "unsigned int flags" parameter instead and a: >> >> #define AHCI_PLATFORM_GET_RESETS 0x01 >> >> And update all callers of ahci_platform_get_resources to pass 0 for flags >> except for drivers/ata/ahci_platform.c. This way we only need to modify >> all callers once, and if we want to add another optional resource in >> the future we can add a: >> >> #define AHCI_PLATFORM_GET_FOO 0x02 >> >> Without needing to change all callers again. > > Indeed. This is more flexible to add another resources. > > Although I'm about to prepare the candidate patch to fix this issue, > I think we need to revert the previous patch first if some SoCs have > issues because of it.
Ack. It is probably best if you do a "git revert f0f56716fc3e5d547fd7811eb218a30ed0695605" on a tree with that commit and then send a patch to Tejun for this.
Regards,
Hans
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