On 15/10/2022 18:53, Simon Glass wrote: > Hi Paul, > > On Sat, 15 Oct 2022 at 03:19, Paul Barker <paul.bar...@sancloud.com> wrote: >> >> We should only perform additional iteration steps when needed to >> initialize the parent of a device. Other binding errors (such as a >> missing driver) should not lead to additional iteration steps. >> >> Unnecessary iteration steps can cause issues when memory is tightly >> constrained (such as in the TPL/SPL) since device_bind_by_name() >> unconditionally allocates memory for a struct udevice. On the SanCloud >> BBE this led to boot failure caused by memory exhaustion in the SPL >> when booting from SPI flash. >> >> Signed-off-by: Paul Barker <paul.bar...@sancloud.com> >> --- >> drivers/core/lists.c | 17 ++++++----------- >> 1 file changed, 6 insertions(+), 11 deletions(-) > > Are you able to construct a test for this? See test/dm/core.c or test-fdt.c
I can't see how to construct a test case for this issue. What I observed
was the SPL crashing during the pre-relocation lists_bind_drivers() call
due to exhaustion of the available memory. On the AM335x SoC this is 64k
of on-board SRAM which is available before main DRAM is initialised. I
can't see how to reproduce this issue within the u-boot test framework
as significantly more memory is available when running the u-boot
sandbox and so memory exhaustion does not occur. If there are other side
effects than memory leaking here then I'm not familiar enough with the
u-boot device model to spot them.
Each call to bind_drivers_pass() calls device_bind_by_name() for every
driver_info record, with no way of checking whether a particular
driver_info record has already been handled by a previous call to
bind_drivers_pass(). This leaks memory as each call to
device_bind_by_name() allocates a new device object.
>
> Also, I think bind_drivers_pass() needs a function comment that
> describes in detail what is going on.
Agreed, I'll see what I can add when I revisit this.
>
> Would it be possible to achieve the same effect while keeping that
> function the same as now? See below.
>
>>
>> diff --git a/drivers/core/lists.c b/drivers/core/lists.c
>> index c49695b24f00..82d479564121 100644
>> --- a/drivers/core/lists.c
>> +++ b/drivers/core/lists.c
>> @@ -51,13 +51,13 @@ struct uclass_driver *lists_uclass_lookup(enum uclass_id
>> id)
>> return NULL;
>> }
>>
>> -static int bind_drivers_pass(struct udevice *parent, bool pre_reloc_only)
>> +static bool bind_drivers_pass(struct udevice *parent, bool pre_reloc_only,
>> + int *result)
>> {
>> struct driver_info *info =
>> ll_entry_start(struct driver_info, driver_info);
>> const int n_ents = ll_entry_count(struct driver_info, driver_info);
>> bool missing_parent = false;
>> - int result = 0;
>> int idx;
>>
>> /*
>> @@ -98,12 +98,12 @@ static int bind_drivers_pass(struct udevice *parent,
>> bool pre_reloc_only)
>> drt->dev = dev;
>> } else if (ret != -EPERM) {
>> dm_warn("No match for driver '%s'\n", entry->name);
>> - if (!result || ret != -ENOENT)
>> - result = ret;
>> + if (!*result || ret != -ENOENT)
>> + *result = ret;
>> }
>> }
>>
>> - return result ? result : missing_parent ? -EAGAIN : 0;
>> + return missing_parent;
>> }
>>
>> int lists_bind_drivers(struct udevice *parent, bool pre_reloc_only)
>> @@ -117,13 +117,8 @@ int lists_bind_drivers(struct udevice *parent, bool
>> pre_reloc_only)
>> * always succeed on the first pass.
>> */
>> for (pass = 0; pass < 10; pass++) {
>> - int ret;
>> -
>> - ret = bind_drivers_pass(parent, pre_reloc_only);
>> - if (!ret)
>> + if (!bind_drivers_pass(parent, pre_reloc_only, &result))
>> break;
>> - if (ret != -EAGAIN && !result)
>> - result = ret;
>
> If there were something like this, could we drop the other changes?
>
> if (ret) {
> if (ret == -EAGAIN)
> continue;
> else if (!result)
>
> result = ret;
> }
I don't think this works exactly, as we want to break when (ret ==
-EAGAIN) instead of continue. However I have a variant which I think is
working which I can send as a v2.
>
>> }
>>
>> return result;
>> --
>> 2.25.1
>>
--
Paul Barker
Principal Software Engineer
SanCloud Ltd
e: paul.bar...@sancloud.com
w: https://sancloud.com/
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