RE: [PATCH] mmc-utils: Implement alternative boot operation

["Christian Löhle" <CLoehle@hyperstone.com>]

>> @@ -255,6 +255,18 @@ static struct Command commands[] = {
>>           "Issues a CMD0 GO_PRE_IDLE",
>>           NULL
>>         },
>> +       { do_alt_boot_op, -1,
>> +         "boot_operation", "<boot_data_file> <boot_blocks> <device>\n"
>> +         "Does the alternative boot operation and writes the 
>> + specified starting
>> blocks of boot data into the requested file.\n\n"
>> +         "Note some limitations\n:"
>> +         "1. The boot operation must be configured, e.g. for legacy speed:\n"
>> +         "mmc-utils bootbus set single_backward retain x8 /dev/mmcblk2\n"
>> +         "mmc-utils bootpart enable 1 0 /dev/mmcblk2\n"
>> +         "2. The MMC must currently be running at the bus mode that 
>> + is
>> configured for the boot operation (HS200 and HS400 not supported at all).\n"
>> +         "3. Most hosts cannot do transfers of the typical size of 
>> + the boot partition,
>> adjust <boot_blocks> accordingly.\n"
> A redundant arg?
> Since blksz is 512, Maybe just set it to be ext_csd[226] * 256?

As the help above explains this will not work on most hosts.
Limitations of maximum transfers of like 512K to a couple MB are very common.
One could just read the max, but I found it less misleading that way.

>> +       mioc->num_of_cmds = 2;
>> +       mioc->cmds[0].opcode = MMC_GO_IDLE_STATE;
>> +       mioc->cmds[0].arg = MMC_GO_PRE_IDLE_STATE_ARG;
>> +       mioc->cmds[0].flags = MMC_RSP_NONE | MMC_CMD_AC;
>> +       mioc->cmds[0].write_flag = 0;
>> +
>> +       mioc->cmds[1].opcode = MMC_GO_IDLE_STATE;
>> +       mioc->cmds[1].arg = MMC_BOOT_INITIATION_ARG;
>> +       mioc->cmds[1].flags = MMC_RSP_NONE | MMC_CMD_ADTC;
>> +       mioc->cmds[1].write_flag = 0;
>> +       mioc->cmds[1].blksz = 512;
>> +       mioc->cmds[1].blocks = boot_blocks;
>> +       /* Access time of boot part differs wildly, spec mandates 1s */
>> +       mioc->cmds[1].data_timeout_ns = 2 * 1000 * 1000 * 1000;
>> +       mmc_ioc_cmd_set_data(mioc->cmds[1], boot_buf);
> Don't you get "010" prior to the boot content?
> Most cards have their EXT_CSD_PART_CONFIG_ACC_ACK bit set.
> So you need to eliminate it from the boot file?
> But your compare show that the files are identical - how so?

By configuring the card to not send BOOT ACK.
With it enabled there is unfortunately no way to get the transfer through from userspace.
(The host will sample part of the ACK, CRC wont match and so on)

I will address the rest of you comments in v2.

Regards,
Christian
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