Re: [PATCH] efi/libstub/arm*: Set default address and size cells values for an empty dtb

Jeffrey Hugo
2017-02-07T18:41:29Z

On 2/7/2017 11:15 AM, Mark Rutland wrote:
> Hi,
>
> On Tue, Feb 07, 2017 at 10:59:50AM -0700, Jeffrey Hugo wrote:
>> From: Sameer Goel <sgoel@codeaurora.org>
>>
>> In cases where a device tree is not provided (ie ACPI based system), an
>> empty fdt is generated by efistub. Sets the address and size cell values
>> in a generated fdt to support 64 bit addressing.
>>
>> This enables kexec/kdump on Qualcomm Technologies QDF24XX platforms as those
>> utilities will read the address/size values from the fdt, and such values
>> may exceed the range provided by the 32 bit default.
>
> The description here doesn't state why this is a problem for ACPI.
>
> What values are being read by the tools, and for what purpose?
>
> Are they extracting data from the DTB, or is this part of inserting a
> new property?
>
> Why does this adversely affect ACPI?

I think the response I am about to send to Ard will address these questions.

>
>> Change-Id: Ie7f3637e375bd6631c6bda1f7b3c9003765ff4a5
>
> Please remove this kind of tags from upstream patches. It's irrelevant.

Yep, sorry about that. I should know better.

>
>> Signed-off-by: Sameer Goel <sgoel@codeaurora.org>
>> Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>
>> ---
>> drivers/firmware/efi/libstub/fdt.c | 38 +++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 37 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
>> index 921dfa0..def5c9c 100644
>> --- a/drivers/firmware/efi/libstub/fdt.c
>> +++ b/drivers/firmware/efi/libstub/fdt.c
>> @@ -16,6 +16,34 @@
>>
>> #include "efistub.h"
>>
>> +#define EFI_DT_ADDR_CELLS_DEFAULT 2
>> +#define EFI_DT_SIZE_CELLS_DEFAULT 2
>> +
>> +static void fdt_update_cell_size(efi_system_table_t *sys_table, void *fdt)
>> +{
>> + int offset;
>> + int status;
>> +
>> + offset = fdt_path_offset(fdt, "/");
>> + /* Set the #address-cells and #size-cells values for an empty tree */
>> +
>> + status = fdt_setprop_u32(fdt, offset, "#address-cells",
>> + EFI_DT_ADDR_CELLS_DEFAULT);
>> + if (status) {
>> + pr_efi(sys_table,
>> + "Failed to set #address-cells for empty dtb\n");
>> + return;
>> + }
>> +
>> + status = fdt_setprop_u32(fdt, offset, "#size-cells",
>> + EFI_DT_SIZE_CELLS_DEFAULT);
>> + if (status) {
>> + pr_efi(sys_table,
>> + "Failed to set #size-cells for empty dtb\n");
>> + return;
>> + }
>> +}
>
> We don't seem to log anything for most other failures within
> update_fdt() where this is called.
>
> Are these really much more special?
>
>> static efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt,
>> unsigned long orig_fdt_size,
>> void *fdt, int new_fdt_size, char *cmdline_ptr,
>> @@ -44,8 +72,16 @@ static efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt,
>>
>> if (orig_fdt)
>> status = fdt_open_into(orig_fdt, fdt, new_fdt_size);
>> - else
>> + else {
>
> Nit: if one side of an if-else has braces, the other should too per the
> usual kernel coding style.

Will fix.

>
> Thanks,
> Mark.
>

--
Jeffrey Hugo
Qualcomm Datacenter Technologies as an affiliate of Qualcomm
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.