confusion regarding the CMD19 and CMD21 in eMMC/SD card spec

[Girish K S]

Hello Aaron Lu,
                    please check the mmc 4.5 specification CMD21 is
tuning command.

regards
Girish K S

On 16 September 2011 10:17, Aaron Lu <aaron.lu at amd.com> wrote:
> On Fri, Sep 16, 2011 at 09:41:04AM +0530, Girish K S wrote:
>> but there is only one host controller to handle these commands.
>> the generic sdhci driver has cmd19 hard coded, thats the reason I
>> asked the question.
>> you can also check it in the function sdhci_execute_tuning it is hard coded as
>> cmd.opcode = MMC_SEND_TUNING_BLOCK; where the macro value is 19.
>> So in case of SD card insertion it will send a SEND_TUNING_BLOCK
>> command to the device. but if
>> MMC card is inserted then it will send a BUS_TEST_W command to the device.
>
> sdhci_execute_tuning will only be called if the inserted card is a sd card
> and it is operating at SDR104 or SDR50 mode(UHS-I).
>
> The host's tuning function is called from the mmc_sd_init_uhs_card,
> and for a mmc card, there is no chance of that function being called.
>
> -Aaron
>
>