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

[Aaron Lu]

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