drivers/mmc/bcmstb_sdhci.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * (C) Copyright 2018  Cisco Systems, Inc.
   4  *
   5  * Author: Thomas Fitzsimmons <fitzsim@fitzsim.org>
   6  */
   7
   8 #include <common.h>
   9 #include <mach/sdhci.h>
  10 #include <malloc.h>
  11 #include <sdhci.h>
  12
  13 /*
  14  * The BCMSTB SDHCI has a quirk in that its actual maximum frequency
  15  * capability is 100 MHz.  The divisor that is eventually written to
  16  * SDHCI_CLOCK_CONTROL is calculated based on what the MMC device
  17  * reports, and relative to this maximum frequency.
  18  *
  19  * This define used to be set to 52000000 (52 MHz), the desired
  20  * maximum frequency, but that would result in the communication
  21  * actually running at 100 MHz (seemingly without issue), which is
  22  * out-of-spec.
  23  *
  24  * Now, by setting this to 0 (auto-detect), 100 MHz will be read from
  25  * the capabilities register, and the resulting divisor will be
  26  * doubled, meaning that the clock control register will be set to the
  27  * in-spec 52 MHz value.
  28  */
  29 #define BCMSTB_SDHCI_MAXIMUM_CLOCK_FREQUENCY    0
  30 /*
  31  * When the minimum clock frequency is set to 0 (auto-detect), U-Boot
  32  * sets it to 100 MHz divided by SDHCI_MAX_DIV_SPEC_300, or 48,875 Hz,
  33  * which results in the controller timing out when trying to
  34  * communicate with the MMC device.  Hard-code this value to 400000
  35  * (400 kHz) to prevent this.
  36  */
  37 #define BCMSTB_SDHCI_MINIMUM_CLOCK_FREQUENCY    400000
  38
  39 static char *BCMSTB_SDHCI_NAME = "bcmstb-sdhci";
  40
  41 /*
  42  * This driver has only been tested with eMMC devices; SD devices may
  43  * not work.
  44  */
  45 int bcmstb_sdhci_init(phys_addr_t regbase)
  46 {
  47         struct sdhci_host *host = NULL;
  48
  49         host = (struct sdhci_host *)malloc(sizeof(struct sdhci_host));
  50         if (!host) {
  51                 printf("%s: Failed to allocate memory\n", __func__);
  52                 return 1;
  53         }
  54         memset(host, 0, sizeof(*host));
  55
  56         host->name = BCMSTB_SDHCI_NAME;
  57         host->ioaddr = (void *)regbase;
  58         host->quirks = 0;
  59
  60         host->cfg.part_type = PART_TYPE_DOS;
  61
  62         host->version = sdhci_readw(host, SDHCI_HOST_VERSION);
  63
  64         return add_sdhci(host,
  65                          BCMSTB_SDHCI_MAXIMUM_CLOCK_FREQUENCY,
  66                          BCMSTB_SDHCI_MINIMUM_CLOCK_FREQUENCY);
  67 }