[U-Boot] [RFC PATCH] arm: bootm: Boot kernel with U-Boot's FDT blob

[Lokesh Vutla]

On Wednesday 11 January 2017 12:50 PM, Michal Simek wrote:
> On 11.1.2017 06:19, Lokesh Vutla wrote:
>>
>>
>> On Tuesday 10 January 2017 06:28 PM, Michal Simek wrote:
>>> U-Boot configured via DTB can use the same DTB for booting the kernel.
>>> When OF_CONTROL is used fdtcontroladdr is setup and can be use for boot.
>>>
>>> Signed-off-by: Michal Simek <michal.simek at xilinx.com>
>>> ---
>>>
>>> Didn't check if there is any side effect or not but it looks weird when
>>> you have DT driver u-boot that you have to load dtb again.
>>>
>>> ---
>>>  arch/arm/lib/bootm.c | 14 ++++++++++++++
>>>  1 file changed, 14 insertions(+)
>>>
>>> diff --git a/arch/arm/lib/bootm.c b/arch/arm/lib/bootm.c
>>> index 43cc83ec95b6..9740045b0094 100644
>>> --- a/arch/arm/lib/bootm.c
>>> +++ b/arch/arm/lib/bootm.c
>>> @@ -245,6 +245,20 @@ static void boot_prep_linux(bootm_headers_t *images)
>>>  		}
>>>  		setup_board_tags(&params);
>>>  		setup_end_tag(gd->bd);
>>> +	} else if (IS_ENABLED(CONFIG_OF_CONTROL)) {
>>> +#ifdef CONFIG_OF_LIBFDT
>>> +		images->ft_addr = (char *)getenv_hex("fdtcontroladdr", 0);
>>
>> If your intent is to use U-Boot's fdt as fallback, why can't we just use
>> gd->fdt_blob instead of getting from env?
> 
> Not an issue to use gd->fdt_block instead but I expect we should copy it
> to the different location too.
> 
>>
>> IMO, this is not the right place to get the fallback fdt. Instead it
>> should fallback at bootm_get_fdt() so that other parameters like
>> images->ft_length is also updated. Can you try the following diff?
> 
> Not a problem to move it to this position.
> 
> I have tried it and system is not booting.

Hmm.. not sure if I am missing something. I am able to boot with this
change and not loading any dtb: http://pastebin.ubuntu.com/23780811/

Thanks and regards,
Lokesh

> 
>>
>> diff --git a/common/image-fdt.c b/common/image-fdt.c
>> index e7540be8d6..f8714b3702 100644
>> --- a/common/image-fdt.c
>> +++ b/common/image-fdt.c
>> @@ -238,7 +238,6 @@ int boot_get_fdt(int flag, int argc, char * const
>> argv[], uint8_t arch,
>>  	int		fdt_noffset;
>>  #endif
>>  	const char *select = NULL;
>> -	int		ok_no_fdt = 0;
>>
>>  	*of_flat_tree = NULL;
>>  	*of_size = 0;
>> @@ -311,7 +310,7 @@ int boot_get_fdt(int flag, int argc, char * const
>> argv[], uint8_t arch,
>>  			       fdt_addr);
>>  			fdt_hdr = image_get_fdt(fdt_addr);
>>  			if (!fdt_hdr)
>> -				goto no_fdt;
>> +				goto fallback_fdt;
>>
>>  			/*
>>  			 * move image data to the load address,
>> @@ -381,7 +380,7 @@ int boot_get_fdt(int flag, int argc, char * const
>> argv[], uint8_t arch,
>>  			break;
>>  		default:
>>  			puts("ERROR: Did not find a cmdline Flattened Device Tree\n");
> 
> 
> This probably requires some code around not to show this error message
> because it should be valid boot option.
> 
>> -			goto no_fdt;
>> +			goto fallback_fdt;
>>  		}
>>
>>  		printf("   Booting using the fdt blob at %#08lx\n", fdt_addr);
>> @@ -415,11 +414,17 @@ int boot_get_fdt(int flag, int argc, char * const
>> argv[], uint8_t arch,
>>  			}
>>  		} else {
>>  			debug("## No Flattened Device Tree\n");
>> -			goto no_fdt;
>> +			goto fallback_fdt;
>>  		}
>>  	} else {
>>  		debug("## No Flattened Device Tree\n");
>> -		goto no_fdt;
>> +		goto fallback_fdt;
>> +	}
>> +
>> +fallback_fdt:
>> +	if (!fdt_blob) {
>> +		printf("## Using U-boot's fdt to boot kernel\n");
>> +		fdt_blob = (char *)gd->fdt_blob;
>>  	}
>>
>>  	*of_flat_tree = fdt_blob;
>> @@ -429,12 +434,10 @@ int boot_get_fdt(int flag, int argc, char * const
>> argv[], uint8_t arch,
>>
>>  	return 0;
>>
>> -no_fdt:
>> -	ok_no_fdt = 1;
>>  error:
>>  	*of_flat_tree = NULL;
>>  	*of_size = 0;
>> -	if (!select && ok_no_fdt) {
>> +	if (!select) {
>>  		debug("Continuing to boot without FDT\n");
>>  		return 0;
>>  	}
>>
>> Thanks and regards,
>> Lokesh
>>
> 
> Thanks,
> Michal
>