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

Thu Jan 10 19:22:25 UTC 2019

On 1/10/19 10:22 AM, Alexander Graf wrote:
> 
> 
>> Am 10.01.2019 um 10:16 schrieb AKASHI Takahiro <takahiro.akashi at 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 at 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 at 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.

Why shouldn't we partially initialize the EFI environment when the first
block device is created?

I think only the memory part of EFI is needed at this stage.

>>
>> This event will be expected to be 'signal'ed at every creation/deletion
>> of UCLASS_BLK device. Right?
> 
> Correct.

Events are not the EFI way of handling drivers. Drivers are connected by
calling ConnectController.

Please, add two new functions in lib/efi_loader/efi_disk.c

* one called after a new block device is created
* another called before a device is destroyed

both passing as argument (struct udevice *dev) and the caller being in
drivers/block/blk-uclass.c

A separate patch has to add a struct udevice *dev field to struct
efi_obj and let efi_block_driver use it to decide if a new device shall
be created when binding.

In efi_block_driver.c we have to implement the unbind function.

In a later patch series we will use said functions to create or destroy
a handle with the EFI_BLOCK_IO_PROTOCOL and wire up ConnectController
and DisconnectController.

Best regards

Heinrich

> 
>>
>>> 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.
> 
>>
>>> 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.
> 
>>
>> 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?
> 
> Alex
> 
> 
> 