SMEM ：shared memory，是高通平臺(tái)各子系統(tǒng)共享信息的一種機(jī)制，通過(guò)SMEM機(jī)制，PBL可以將信息傳遞給SBL1，SBL1可以將信息傳遞給RPM、LK。下面分析一個(gè)SMEM信息傳遞的具體實(shí)現(xiàn)過(guò)程。

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1 Platform id信息

SBL1會(huì)將board level platform id信息通過(guò)SMEM機(jī)制保存，LK在啟動(dòng)過(guò)程中會(huì)自動(dòng)platform detect，檢測(cè)當(dāng)前平臺(tái)board infor信息，根據(jù)檢測(cè)到的board infor加載相應(yīng)的device tree

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SBL1:從emmc中讀取platform id等CDT信息，并保存到約定的smem中

voidboot_config_data_table_init(bl_shared_data_type* bl_shared_data)

{

? /*populate configuration data table's info*/

? config_data_table_info.size =config_data_table_size;

? config_data_table_info.cdt_ptr =config_data_table; //platform id & ddr default parameter

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?boot_update_config_data_table(&config_data_table_info);

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? /*put a pointer to the table info into sblshared data so next sbl can access it*/

?bl_shared_data->sbl_shared_data->config_data_table_info =&config_data_table_info;

}

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LK通過(guò)讀取smem獲取platform infor信息

static void platform_detect()

{

????????????? ret= smem_read_alloc_entry(SMEM_BOARD_INFO_LOCATION,

??????????????????????????? &board_info_v8,

??????????????????????????? board_info_len);

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????????????? board.platform= board_info_v8.board_info_v3.msm_id;

????????????? board.platform_version= board_info_v8.board_info_v3.msm_version;

????????????? board.platform_hw= board_info_v8.board_info_v3.hw_platform;

????????????? board.platform_subtype= board_info_v8.platform_subtype;

}

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同理，SBL1可通過(guò)SMEM將DDR default parameter傳遞給RPM，當(dāng)然也可以將OEM定制信息通過(guò)SMEM保存，在啟動(dòng)階段根據(jù)不同OEM信息進(jìn)行相應(yīng)的特制化。

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2 如何在SBL1和LK間通過(guò)SMEM傳遞客制化信息

step1. Add a new enum (i.e?SMEM_OEM_MAGIC_INFO = XXX)in?smem_mem_type?

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step 2. After the?boot_smem_init() is called, you use?smem_alloc()?to allocate the SMEM space for your data,i.e:

• smem_oem_magic_ptr = (uint32 *) smem_alloc( SMEM_OEM_MAGIC_INFO, sizeof(uint32));

step3. On lk side add a new enum (i.e?SMEM_OEM_MAGIC_INFO =XXX) in?smem_mem_type_t

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step4. In lk code, you can usethe?smem_read_alloc_entry()?to read data which is passed from SBL1,i.e:

• smem_read_alloc_entry( SMEM_OEM_MAGIC_INFO,&apps_oem_magic_info, sizeof(?uint32));

總結(jié)

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