Re: [RESEND PATCH v2 1/2] pstore: Add mem_type property DT parsing support

[Mukesh Ojha <mojha@codeaurora.org>]

Hi All,

can you please review this ?

Thanks,

Mukesh

On 3/2/2021 1:59 PM, Mukesh Ojha wrote:
> Hi Kees,
>
> i have updated the patch based on your last comments.
> please review.
>
> Thanks,
> Mukesh
>
> On 2/25/2021 9:30 PM, Mukesh Ojha wrote:
>> There could be a sceanario where we define some region
>> in normal memory and use them store to logs which is later
>> retrieved by bootloader during warm reset.
>>
>> In this scenario, we wanted to treat this memory as normal
>> cacheable memory instead of default behaviour which
>> is an overhead. Making it cacheable could improve
>> performance.
>>
>> This commit gives control to change mem_type from Device
>> tree, and also documents the value for normal memory.
>>
>> Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>
>> ---
>> Changes in v2:
>>   - if-else converted to switch case
>>   - updated MODULE_PARM_DESC with new memory type.
>>   - default setting is still intact.
>>
>>   Documentation/admin-guide/ramoops.rst |  4 +++-
>>   fs/pstore/ram.c                       |  3 ++-
>>   fs/pstore/ram_core.c                  | 18 ++++++++++++++++--
>>   3 files changed, 21 insertions(+), 4 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/ramoops.rst 
>> b/Documentation/admin-guide/ramoops.rst
>> index b0a1ae7..8f107d8 100644
>> --- a/Documentation/admin-guide/ramoops.rst
>> +++ b/Documentation/admin-guide/ramoops.rst
>> @@ -3,7 +3,7 @@ Ramoops oops/panic logger
>>     Sergiu Iordache <sergiu@chromium.org>
>>   -Updated: 17 November 2011
>> +Updated: 10 Feb 2021
>>     Introduction
>>   ------------
>> @@ -30,6 +30,8 @@ mapping to pgprot_writecombine. Setting 
>> ``mem_type=1`` attempts to use
>>   depends on atomic operations. At least on ARM, pgprot_noncached 
>> causes the
>>   memory to be mapped strongly ordered, and atomic operations on 
>> strongly ordered
>>   memory are implementation defined, and won't work on many ARMs such 
>> as omaps.
>> +Setting ``mem_type=2`` attempts to treat the memory region as normal 
>> memory,
>> +which enables full cache on it. This can improve the performance.
>>     The memory area is divided into ``record_size`` chunks (also 
>> rounded down to
>>   power of two) and each kmesg dump writes a ``record_size`` chunk of
>> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
>> index ca6d8a8..af4ca6a4 100644
>> --- a/fs/pstore/ram.c
>> +++ b/fs/pstore/ram.c
>> @@ -56,7 +56,7 @@ MODULE_PARM_DESC(mem_size,
>>   static unsigned int mem_type;
>>   module_param(mem_type, uint, 0400);
>>   MODULE_PARM_DESC(mem_type,
>> -        "set to 1 to try to use unbuffered memory (default 0)");
>> +        "set to 1 to use unbuffered memory, 2 for cached memory 
>> (default 0)");
>>     static int ramoops_max_reason = -1;
>>   module_param_named(max_reason, ramoops_max_reason, int, 0400);
>> @@ -666,6 +666,7 @@ static int ramoops_parse_dt(struct 
>> platform_device *pdev,
>>           field = value;                        \
>>       }
>>   +    parse_u32("mem-type", pdata->record_size, pdata->mem_type);
>>       parse_u32("record-size", pdata->record_size, 0);
>>       parse_u32("console-size", pdata->console_size, 0);
>>       parse_u32("ftrace-size", pdata->ftrace_size, 0);
>> diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
>> index aa8e0b6..0da012f 100644
>> --- a/fs/pstore/ram_core.c
>> +++ b/fs/pstore/ram_core.c
>> @@ -396,6 +396,10 @@ void persistent_ram_zap(struct 
>> persistent_ram_zone *prz)
>>       persistent_ram_update_header_ecc(prz);
>>   }
>>   +#define MEM_TYPE_WCOMBINE    0
>> +#define MEM_TYPE_NONCACHED    1
>> +#define MEM_TYPE_NORMAL        2
>> +
>>   static void *persistent_ram_vmap(phys_addr_t start, size_t size,
>>           unsigned int memtype)
>>   {
>> @@ -409,10 +413,20 @@ static void *persistent_ram_vmap(phys_addr_t 
>> start, size_t size,
>>       page_start = start - offset_in_page(start);
>>       page_count = DIV_ROUND_UP(size + offset_in_page(start), 
>> PAGE_SIZE);
>>   -    if (memtype)
>> +    switch (memtype) {
>> +    case MEM_TYPE_NORMAL:
>> +        prot = PAGE_KERNEL;
>> +        break;
>> +    case MEM_TYPE_NONCACHED:
>>           prot = pgprot_noncached(PAGE_KERNEL);
>> -    else
>> +        break;
>> +    case MEM_TYPE_WCOMBINE:
>>           prot = pgprot_writecombine(PAGE_KERNEL);
>> +        break;
>> +    default:
>> +        pr_err("invalid memory type\n");
>> +        return NULL;
>> +    }
>>         pages = kmalloc_array(page_count, sizeof(struct page *), 
>> GFP_KERNEL);
>>       if (!pages) {