linux-kernel - Re: [PATCH V0 1/1] bootconfig: Increase max size of bootconfig from 32 KB to 256 KB for DCC support

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Message-ID: <e2ac0fa4-28f0-f4d8-e02a-b2a5d6131a48@quicinc.com>
Date:   Tue, 10 Jan 2023 17:26:07 +0530
From:   Souradeep Chowdhury <quic_schowdhu@...cinc.com>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
CC:     <linux-kernel@...r.kernel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-arm-msm@...r.kernel.org>,
        "Sai Prakash Ranjan" <quic_saipraka@...cinc.com>,
        Sibi Sankar <quic_sibis@...cinc.com>,
        Rajendra Nayak <quic_rjendra@...cinc.com>
Subject: Re: [PATCH V0 1/1] bootconfig: Increase max size of bootconfig from
 32 KB to 256 KB for DCC support



On 1/9/2023 8:48 PM, Masami Hiramatsu (Google) wrote:
> On Mon, 9 Jan 2023 20:01:05 +0530
> Souradeep Chowdhury <quic_schowdhu@...cinc.com> wrote:
> 
>> Increasing the memory size of bootconfig to be able to handle a max number of
>> 8192 nodes to be fitted in memory size of 256KB.
> 
> Sorry, but you missed the 'xbc_node::data' stores the index of the data and
> that is uint16_t. So the XBC_DATA_MAX is fixed limitation.
> 
> The number of nodes (XBC_NODE_MAX) can be expanded because I just decided it
> to keep the pre-compiled array size ~8KB. Maybe expanding it to 64KB just
> increase the size of kernel on init memory (and freed after boot).
> 
> Could you tell me why you need such a big data for your DCC?
> 
> Thank you,

DCC is a debugging tool used in qcom which is needed to debug crashes
that can happen at boot-time. For debugging purposes a large number of
registers need to be configured in DCC driver which is to be fed via the
bootconfig file. For that we need to expand the nodes as well as memory
for using bootconfig.
Can you let us know the changes that you suggest for doing the same? Is 
it fine to just increase the XBC_NODE_MAX, do we also need to
change the uint16_t to u32 for proper storing of index values?


> 
>>
>> Signed-off-by: Souradeep Chowdhury <quic_schowdhu@...cinc.com>
>> ---
>>   include/linux/bootconfig.h | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/linux/bootconfig.h b/include/linux/bootconfig.h
>> index 1611f9d..64d233b 100644
>> --- a/include/linux/bootconfig.h
>> +++ b/include/linux/bootconfig.h
>> @@ -55,11 +55,11 @@ struct xbc_node {
>>   } __attribute__ ((__packed__));
>>   
>>   #define XBC_KEY		0
>> -#define XBC_VALUE	(1 << 15)
>> -/* Maximum size of boot config is 32KB - 1 */
>> +#define XBC_VALUE	(1 << 18)
>> +/* Maximum size of boot config is 256KB - 1 */
>>   #define XBC_DATA_MAX	(XBC_VALUE - 1)
>>   
>> -#define XBC_NODE_MAX	1024
>> +#define XBC_NODE_MAX	8192
>>   #define XBC_KEYLEN_MAX	256
>>   #define XBC_DEPTH_MAX	16
>>   
>> -- 
>> 2.7.4
>>
> 
>