target/linux/brcm2708/patches-4.14/950-0166-mmc-bcm2835-sdhost-Support-underclocking.patch

   1 From c03a6b0585e7c469c199d349405b3967bcf18672 Mon Sep 17 00:00:00 2001
   2 From: Phil Elwell <phil@raspberrypi.org>
   3 Date: Mon, 22 Jan 2018 12:17:27 +0000
   4 Subject: [PATCH 166/454] mmc: bcm2835-sdhost: Support underclocking
   5
   6 Support underclocking of the SD bus in two ways:
   7 1. using the max-frequency DT property (which currently has no DT
   8    parameter), and
   9 2. using the exiting sd_overclock parameter.
  10
  11 The two methods differ slightly - in the former the MMC subsystem is
  12 aware of the underclocking, while in the latter it isn't - but the
  13 end results should be the same.
  14
  15 See: https://github.com/raspberrypi/linux/issues/2350
  16
  17 Signed-off-by: Phil Elwell <phil@raspberrypi.org>
  18 ---
  19  drivers/mmc/host/bcm2835-sdhost.c | 6 +++---
  20  1 file changed, 3 insertions(+), 3 deletions(-)
  21
  22 --- a/drivers/mmc/host/bcm2835-sdhost.c
  23 +++ b/drivers/mmc/host/bcm2835-sdhost.c
  24 @@ -1519,8 +1519,7 @@ void bcm2835_sdhost_set_clock(struct bcm
  25         if (host->debug)
  26                 pr_info("%s: set_clock(%d)\n", mmc_hostname(host->mmc), clock);
  27
  28 -       if ((host->overclock_50 > 50) &&
  29 -           (clock == 50*MHZ))
  30 +       if (host->overclock_50 && (clock == 50*MHZ))
  31                 clock = host->overclock_50 * MHZ + (MHZ - 1);
  32
  33         /* The SDCDIV register has 11 bits, and holds (div - 2).
  34 @@ -1894,7 +1893,8 @@ int bcm2835_sdhost_add_host(struct bcm28
  35
  36         mmc = host->mmc;
  37
  38 -       mmc->f_max = host->max_clk;
  39 +       if (!mmc->f_max || mmc->f_max > host->max_clk)
  40 +               mmc->f_max = host->max_clk;
  41         mmc->f_min = host->max_clk / SDCDIV_MAX_CDIV;
  42
  43         mmc->max_busy_timeout =  (~(unsigned int)0)/(mmc->f_max/1000);