[U-Boot] [PATCH v2 2/3] efi_loader: enumerate disk devices every time

[AKASHI Takahiro <takahiro.akashi@linaro.org>]

Alex, Heinrich and Simon,

Thank you for your comments, they are all valuable but also make me
confused as different people have different requirements :)
I'm not sure that all of us share the same *ultimate* goal here.

So, first, let me reply to each of your comments.
Through this process, I hope we will have better understandings
of long-term solution as well as a tentative fix.

On Thu, Jan 10, 2019 at 10:22:04AM +0100, Alexander Graf wrote:
> 
> 
> > Am 10.01.2019 um 10:16 schrieb AKASHI Takahiro <takahiro.akashi@linaro.org>:
> > 
> >> On Thu, Jan 10, 2019 at 09:15:36AM +0100, Alexander Graf wrote:
> >> 
> >> 
> >>>> Am 10.01.2019 um 09:02 schrieb AKASHI Takahiro <takahiro.akashi@linaro.org>:
> >>>> 
> >>>> On Thu, Jan 10, 2019 at 08:30:13AM +0100, Alexander Graf wrote:
> >>>> 
> >>>> 
> >>>>> On 10.01.19 08:26, AKASHI Takahiro wrote:
> >>>>> Alex,
> >>>>> 
> >>>>>> On Thu, Jan 10, 2019 at 07:21:12AM +0100, Alexander Graf wrote:
> >>>>>> 
> >>>>>> 
> >>>>>>> On 10.01.19 03:13, AKASHI Takahiro wrote:
> >>>>>>> Alex,
> >>>>>>> 
> >>>>>>>> On Wed, Jan 09, 2019 at 10:06:16AM +0100, Alexander Graf wrote:
> >>>>>>>> 
> >>>>>>>> 
> >>>>>>>>> On 13.12.18 08:58, AKASHI Takahiro wrote:
> >>>>>>>>> Heinrich,
> >>>>>>>>> 
> >>>>>>>>>>> On Tue, Dec 11, 2018 at 08:55:41PM +0100, Heinrich Schuchardt wrote:
> >>>>>>>>>>> On 11/15/18 5:58 AM, AKASHI Takahiro wrote:
> >>>>>>>>>>> Currently, efi_init_obj_list() scan disk devices only once, and never
> >>>>>>>>>>> change a list of efi disk devices. This will possibly result in failing
> >>>>>>>>>>> to find a removable storage which may be added later on. See [1].
> >>>>>>>>>>> 
> >>>>>>>>>>> In this patch, called is efi_disk_update() which is responsible for
> >>>>>>>>>>> re-scanning UCLASS_BLK devices and removing/adding efi disks if necessary.
> >>>>>>>>>>> 
> >>>>>>>>>>> For example,
> >>>>>>>>>>> 
> >>>>>>>>>>> => efishell devices
> >>>>>>>>>>> Scanning disk pci_mmc.blk...
> >>>>>>>>>>> Found 3 disks
> >>>>>>>>>>> Device Name
> >>>>>>>>>>> ============================================
> >>>>>>>>>>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)
> >>>>>>>>>>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/SD(0)
> >>>>>>>>>>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/SD(0)/HD(2,MBR,0x086246ba,0x40800,0x3f800)
> >>>>>>>>>>> => usb start
> >>>>>>>>>>> starting USB...
> >>>>>>>>>>> USB0:   USB EHCI 1.00
> >>>>>>>>>>> scanning bus 0 for devices... 3 USB Device(s) found
> >>>>>>>>>>>      scanning usb for storage devices... 1 Storage Device(s) found
> >>>>>>>>>>> => efishell devices
> >>>>>>>>>>> Scanning disk usb_mass_storage.lun0...
> >>>>>>>>>>> Device Name
> >>>>>>>>>>> ============================================
> >>>>>>>>>>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)
> >>>>>>>>>>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/SD(0)
> >>>>>>>>>>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/SD(0)/HD(2,MBR,0x086246ba,0x40800,0x3f800)
> >>>>>>>>>>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/USBClass(0,0,9,0,1)/USBClass(46f4,1,0,0,0)/HD(1,0x01,0,0x40,0x14fe4c)
> >>>>>>>>>>> 
> >>>>>>>>>>> Without this patch, the last device, USB mass storage, won't show up.
> >>>>>>>>>>> 
> >>>>>>>>>>> [1] https://lists.denx.de/pipermail/u-boot/2018-October/345307.html
> >>>>>>>>>>> 
> >>>>>>>>>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> >>>>>>>>>> 
> >>>>>>>>>> Why should we try to fix something in the EFI subsystems that goes wrong
> >>>>>>>>>> in the handling of device enumeration.
> >>>>>>>>> 
> >>>>>>>>> No.
> >>>>>>>>> This is a natural result from how efi disks are currently implemented on u-boot.
> >>>>>>>>> Do you want to totally re-write/re-implement efi disks?
> >>>>>>>> 
> >>>>>>>> Could we just make this event based for now? Call a hook from the
> >>>>>>>> storage dm subsystem when a new u-boot block device gets created to
> >>>>>>>> issue a sync of that in the efi subsystem?
> >>>>>>> 
> >>>>>>> If I correctly understand you, your suggestion here corresponds
> >>>>>>> with my proposal#3 in [1] while my current approach is #2.
> >>>>>>> 
> >>>>>>> [1] https://lists.denx.de/pipermail/u-boot/2018-October/345307.html
> >>>>>> 
> >>>>>> Yes, I think so.
> >>>>>> 
> >>>>>>> So we will call, say, efi_disk_create(struct udevice *) in
> >>>>>>> blk_create_device() and efi_dsik_delete() in blk_unbind_all().
> >>>>>> 
> >>>>>> I would prefer if we didn't call them directly, but through an event
> >>>>>> mechanism. So the efi_disk subsystem registers an event with the dm
> >>>>>> block subsystem and that will just call all events when block devices
> >>>>>> get created which will automatically also include the efi disk creation
> >>>>>> callback. Same for reverse.
> >>>>> 
> >>>>> Do you mean efi event by "event?"
> >>>>> (I don't think there is any generic event interface on DM side.)
> >>>>> 
> >>>>> Whatever an "event" is or whether we call efi_disk_create() directly
> >>>>> or indirectly via an event, there is one (big?) issue in this approach
> >>>>> (while I've almost finished prototyping):
> >>>>> 
> >>>>> We cannot call efi_disk_create() within blk_create_device() because
> >>>>> some data fields of struct blk_desc, which are to be used by efi disk,
> >>>>> are initialized *after* blk_create_device() in driver side.
> >>>>> 
> >>>>> So we need to add a hook at/after every occurrence of blk_create_device()
> >>>>> on driver side. For example,
> >>>>> 
> >>>>> === drivers/scsi/scsi.c ===
> >>>>> int do_scsi_scan_one(struct udevice *dev, int id, int lun, bool verbose)
> >>>>> {
> >>>>>   ...
> >>>>>   ret = blk_create_devicef(dev, "scsi_blk", str, IF_TYPE_SCSI, -1,
> >>>>>                  bd.blksz, bd.lba, &bdev);
> >>>>>   ...
> >>>>>   bdesc = dev_get_uclass_platdata(bdev);
> >>>>>   bdesc->target = id;
> >>>>>   bdesc->lun = lun;
> >>>>>   ...
> >>>>> 
> >>>>>   /*
> >>>>>    * We need have efi_disk_create() called here because bdesc->target
> >>>>>    * and lun will be used by dp helpers in efi_disk_add_dev().
> >>>>>    */
> >>>>>   efi_disk_create(bdev);
> >>>>> }
> >>>>> 
> >>>>> int scsi_scan_dev(struct udevice *dev, bool verbose)
> >>>>> {
> >>>>>       for (i = 0; i < uc_plat->max_id; i++)
> >>>>>               for (lun = 0; lun < uc_plat->max_lun; lun++)
> >>>>>                       do_scsi_scan_one(dev, i, lun, verbose);
> >>>>>   ...
> >>>>> }
> >>>>> 
> >>>>> int scsi_scan(bool verbose)
> >>>>> {
> >>>>>   ret = uclass_get(UCLASS_SCSI, &uc);
> >>>>>   ...
> >>>>>       uclass_foreach_dev(dev, uc)
> >>>>>               ret = scsi_scan_dev(dev, verbose);
> >>>>>   ...
> >>>>> }
> >>>>> === ===
> >>>>> 
> >>>>> Since scsn_scan() can be directly called by "scsi rescan" command,
> >>>>> There seems to be no generic hook, or event, available in order to
> >>>>> call efi_disk_create().
> >>>>> 
> >>>>> Do I miss anything?
> >>>> 
> >>>> Could the event handler that gets called from somewhere around
> >>>> blk_create_device() just put it into an efi internal "todo list" which
> >>>> we then process using an efi event?
> >>>> 
> >>>> EFI events will only get triggered on the next entry to efi land, so by
> >>>> then we should be safe.
> >>> 
> >>> I think I now understand your suggestion; we are going to invent
> >>> a specialized event-queuing mechanism so that we can take any actions
> >>> later at appropriate time (probably in efi_init_obj_list()?).
> >> 
> >> Uh, not sure I follow. There would be 2 events. One from the u-boot block layer to the efi_loader disk layer.
> > 
> > This is a to-be-invented "specialized event-queuing mechanism"
> > in my language :) as we cannot use efi_create/signal_event() before
> > initializing EFI environment.
> > 
> > This event will be expected to be 'signal'ed at every creation/deletion
> > of UCLASS_BLK device. Right?
> 
> Correct.
> 
> > 
> >> That event handler creates a new efi event (like a timer w/ timeout=0).
> > 
> > But when is this event handler fired?
> > I think the only possible timing is at efi_init_obj_list().
> 
> We already walk through the event list on any u-boot/efi world switch.

? Where is the code?

> > 
> >> This new event's handler can then create the actual efi block device.
> > 
> > I assume that this event handler is fired immediately after
> > efi_signal_event() with timeout=0.
> 
> Right, and that signal_event() will happen the next time we go back into efi land. By that time, the dm blk struct will be complete.

This will be true.

> > 
> > If so, why do we need to create an efi event? To isolate the disk code
> > from the other init code?
> 
> I don't think we should call init code during runtime, yes. These are 2 paths.
> 
> > 
> > (If so, for the same reason, we should re-write efi_init_obj_list()
> > with events for other efi resources as well.)
> > 
> >>> 
> >>> But if so, it's not much different from my current approach where
> >>> a list of efi disks are updated in efi_init_obj_list() :)
> >> 
> >> The main difference is that disk logic stays in the disc code scope :).
> > 
> > My efi_disk_update() (and efi_disk_register()) is the only function
> > visible outside the disk code, isn't it?
> > 
> > Using some kind of events here is smart, but looks to me a bit overdoing
> > because we anyhow have to go through all the UCLASS_BLK devices to mark
> > whether they are still valid or not :)
> 
> What do you mean?

"all the UCLASS_BLK deivces" -> all efi_disk_obj's

Let me rephrase it;
all efi_disk_obj's will be re-visisted in efi_init_obj_list() to determine
its backing u-boot block device is still valid.
If not valid, a said efi_disk_obj should be marked so to prevent further
accessing in efi world.

-Takahiro Akashi

> Alex
> 
>