From mboxrd@z Thu Jan 1 00:00:00 1970 From: aaron.lu@amd.com (Aaron Lu) Date: Fri, 16 Sep 2011 12:47:08 +0800 Subject: confusion regarding the CMD19 and CMD21 in eMMC/SD card spec In-Reply-To: References: <0356427A-B949-4DA6-9F5D-FE0DD54AEDFF@marvell.com> Message-ID: <20110916044706.GA4030@lovegaga> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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