From ce69d37b7d8fa692c45d71d94aa0c921859b82ce Mon Sep 17 00:00:00 2001 From: Ulf Hansson Date: Mon, 16 Sep 2013 11:28:42 +0200 Subject: mmc: core: Prevent violation of specs while initializing cards According to eMMC/SD/SDIO specs, the VDD (VCC) voltage level must be maintained during the initialization sequence. If we want/need to tune the voltage level, a complete power cycle of the card must be executed. Most host drivers conforms to the specifications by only allowing to change VDD voltage level at the MMC_POWER_UP state, but some also cares about MMC_POWER_ON state, which they should'nt. This patch will not break those drivers, but they could clean up code to better reflect what is expected from the protocol layer. A big re-work of the mmc_select_voltage function is done to only change VDD voltage level if the host supports MMC_CAP2_FULL_PWR_CYCLE. Otherwise only validation of the host and card ocr mask will be done. A very nice side-effect of this patch is that we now don't need to reset the negotiated ocr mask at the mmc_power_off function, since now it will actually reflect the present voltage level, which safely can be used at the next power up and re-initialization. Moreover, we then only need to execute mmc_select_voltage from the attach sequence. Signed-off-by: Ulf Hansson Signed-off-by: Chris Ball --- drivers/mmc/core/sd.c | 1 - 1 file changed, 1 deletion(-) (limited to 'drivers/mmc/core/sd.c') diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c index 398065c57edf..53db60a76dae 100644 --- a/drivers/mmc/core/sd.c +++ b/drivers/mmc/core/sd.c @@ -1103,7 +1103,6 @@ static int mmc_sd_resume(struct mmc_host *host) mmc_claim_host(host); mmc_power_up(host, host->card->ocr); - mmc_select_voltage(host, host->card->ocr); err = mmc_sd_init_card(host, host->card->ocr, host->card); mmc_release_host(host); -- cgit v1.2.3