Re: [PATCH] riscv: Generate devicetree only after machine initialization is complete

[Daniel Henrique Barboza <dbarboza@ventanamicro.com>]

On 7/3/23 18:18, Guenter Roeck wrote:
> On 7/3/23 12:25, Daniel Henrique Barboza wrote:
>> On 7/3/23 00:46, Guenter Roeck wrote:
>>> If the devicetree is created before machine initialization is complete,
>>> it misses dynamic devices. Specifically, the tpm device is not added
>>> to the devicetree file and is therefore not instantiated in Linux.
>>> Create devicetree in virt_machine_done() to solve the problem.
>>>
>>> Cc: Alistair Francis <alistair23@gmail.com>
>>> Fixes: 325b7c4e75 hw/riscv: Enable TPM backends
>>> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
>>> ---
>>>   hw/riscv/virt.c | 9 ++++++---
>>>   1 file changed, 6 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
>>> index ed4c27487e..08876284f5 100644
>>> --- a/hw/riscv/virt.c
>>> +++ b/hw/riscv/virt.c
>>> @@ -1248,6 +1248,11 @@ static void virt_machine_done(Notifier *notifier, void *data)
>>>       uint64_t kernel_entry = 0;
>>>       BlockBackend *pflash_blk0;
>>> +    /* create devicetree if not provided */
>>> +    if (!machine->dtb) {
>>> +        create_fdt(s, memmap);
>>> +    }
>>> +
>>
>> I suggest moving the entire load/create DT code from virt_machine_init() to
>> the start of virt_machine_done():
>>
>>      /* load/create device tree */
>>      if (machine->dtb) {
>>          machine->fdt = load_device_tree(machine->dtb, &s->fdt_size);
>>          if (!machine->fdt) {
>>              error_report("load_device_tree() failed");
>>              exit(1);
>>          }
>>      } else {
>>          create_fdt(s, memmap);
>>      }
>>
>> This way we don't have to look in to 2 different functions to wonder what happens
>> in case machine->dtb is NULL.
>>
> 
> I can do that, but I don't know how to test it. Is there a working dtb/machine
> combination for riscv which would let me test loading a devicetree file ?

I recommend using your own setup with TPM (I'm assuming you're using a TPM setup),
generate a .dtb from it, and then launch it using '-dtb'.

First you need the patch applied (otherwise there won't be a TPM in the FDT).
After that, relaunch the same machine again but appending in the end of the
command line:

-machine dumpdtb=file.dtb

This will create a 'file.dtb' file in the working dir and exit. After that re-launch
the machine again but now append:

-dtb file.dtb

And you should be able to boot a 'virt' machine with TPM support.


Thanks,

Daniel



> 
> Guenter
>