From c03a6b0585e7c469c199d349405b3967bcf18672 Mon Sep 17 00:00:00 2001 From: Phil Elwell Date: Mon, 22 Jan 2018 12:17:27 +0000 Subject: [PATCH 166/454] mmc: bcm2835-sdhost: Support underclocking Support underclocking of the SD bus in two ways: 1. using the max-frequency DT property (which currently has no DT parameter), and 2. using the exiting sd_overclock parameter. The two methods differ slightly - in the former the MMC subsystem is aware of the underclocking, while in the latter it isn't - but the end results should be the same. See: https://github.com/raspberrypi/linux/issues/2350 Signed-off-by: Phil Elwell --- drivers/mmc/host/bcm2835-sdhost.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/drivers/mmc/host/bcm2835-sdhost.c +++ b/drivers/mmc/host/bcm2835-sdhost.c @@ -1519,8 +1519,7 @@ void bcm2835_sdhost_set_clock(struct bcm if (host->debug) pr_info("%s: set_clock(%d)\n", mmc_hostname(host->mmc), clock); - if ((host->overclock_50 > 50) && - (clock == 50*MHZ)) + if (host->overclock_50 && (clock == 50*MHZ)) clock = host->overclock_50 * MHZ + (MHZ - 1); /* The SDCDIV register has 11 bits, and holds (div - 2). @@ -1894,7 +1893,8 @@ int bcm2835_sdhost_add_host(struct bcm28 mmc = host->mmc; - mmc->f_max = host->max_clk; + if (!mmc->f_max || mmc->f_max > host->max_clk) + mmc->f_max = host->max_clk; mmc->f_min = host->max_clk / SDCDIV_MAX_CDIV; mmc->max_busy_timeout = (~(unsigned int)0)/(mmc->f_max/1000);