target/linux/s3c24xx/patches-2.6.26/1215-add-limit-sdcard-clk-cmdline.patch.patch

   1 From 96f9902ff40b2124fbe34eeac727c596e7701702 Mon Sep 17 00:00:00 2001
   2 From: Andy Green <andy@openmoko.com>
   3 Date: Fri, 25 Jul 2008 23:06:20 +0100
   4 Subject: [PATCH] add-limit-sdcard-clk-cmdline.patch
   5
   6 This patch allows you to control the maximum clock rate that will
   7 be selected for SD Card access, from the kernel commandline using
   8
   9  glamo_mci.sd_max_clk=10000000
  10
  11 and also from
  12
  13  echo 10000000 > /sys/module/glamo_mci/parameters/sd_max_clk
  14
  15 although you have to suspend and resume to make the limit operational
  16 on the actual SD_CLK line.
  17
  18 Clocks that are possible are divided down from ~50MHz, so 25000000,
  19 16666666, 12500000, 10000000, etc.  With Freerunner A5 revision that
  20 has 100R series resistors in SD Card signals, I didn't get reliable
  21 operation above 16MHz.  With A6 revision the series resistors went
  22 down to 75R, maybe it can work at 25MHz.
  23
  24 Reducing the clock rate is something to try if you find that your
  25 SD Card is not communicating properly with the default speed.
  26
  27 Signed-off-by: Andy Green <andy@openmoko.com>
  28 ---
  29  drivers/mfd/glamo/glamo-mci.c |   38 +++++++++++++++++++++++++++++---------
  30  1 files changed, 29 insertions(+), 9 deletions(-)
  31
  32 diff --git a/drivers/mfd/glamo/glamo-mci.c b/drivers/mfd/glamo/glamo-mci.c
  33 index b53827e..67bb815 100644
  34 --- a/drivers/mfd/glamo/glamo-mci.c
  35 +++ b/drivers/mfd/glamo/glamo-mci.c
  36 @@ -40,6 +40,24 @@ static spinlock_t clock_lock;
  37
  38  static void glamo_mci_send_request(struct mmc_host *mmc);
  39
  40 +/*
  41 + * Max SD clock rate
  42 + *
  43 + * held at /(3 + 1) due to concerns of 100R recommended series resistor
  44 + * allows 16MHz @ 4-bit --> 8MBytes/sec raw
  45 + *
  46 + * you can override this on kernel commandline using
  47 + *
  48 + *   glamo_mci.sd_max_clk=10000000
  49 + *
  50 + * for example
  51 + */
  52 +
  53 +static int sd_max_clk = 50000000 / 3;
  54 +module_param(sd_max_clk, int, 0644);
  55 +
  56 +
  57 +
  58  unsigned char CRC7(u8 * pu8, int cnt)
  59  {
  60         u8 crc = 0;
  61 @@ -676,9 +694,9 @@ static void glamo_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
  62             (ios->power_mode == MMC_POWER_UP)) {
  63                 dev_info(&host->pdev->dev,
  64                         "powered (vdd = %d) clk: %lukHz div=%d (req: %ukHz). "
  65 -                       "Bus width=%d\n",ios->vdd,
  66 -                       host->real_rate / 1000, host->real_rate,
  67 -                       ios->clock / 1000, ios->bus_width);
  68 +                       "Bus width=%d\n",(int)ios->vdd,
  69 +                       host->real_rate / 1000, (int)host->clk_div,
  70 +                       ios->clock / 1000, (int)ios->bus_width);
  71         } else
  72                 dev_info(&host->pdev->dev, "glamo_mci_set_ios: power down.\n");
  73
  74 @@ -800,11 +818,7 @@ static int glamo_mci_probe(struct platform_device *pdev)
  75                           MMC_CAP_MMC_HIGHSPEED |
  76                           MMC_CAP_SD_HIGHSPEED;
  77         mmc->f_min      = host->clk_rate / 256;
  78 -       /*
  79 -        * held at /4 due to concerns of 100R recommended series resistor
  80 -        * allows 16MHz @ 4-bit --> 8MBytes/sec raw
  81 -        */
  82 -       mmc->f_max      = host->clk_rate / 3;
  83 +       mmc->f_max      = sd_max_clk;
  84
  85         mmc->max_blk_count      = (1 << 16) - 1; /* GLAMO_REG_MMC_RB_BLKCNT */
  86         mmc->max_blk_size       = (1 << 12) - 1; /* GLAMO_REG_MMC_RB_BLKLEN */
  87 @@ -866,12 +880,18 @@ static int glamo_mci_suspend(struct platform_device *dev, pm_message_t state)
  88  {
  89         struct mmc_host *mmc = platform_get_drvdata(dev);
  90         struct glamo_mci_host   *host = mmc_priv(mmc);
  91 +       int ret;
  92
  93         host->suspending++;
  94         if (host->pdata->mci_all_dependencies_resumed)
  95                 (host->pdata->mci_suspending)(dev);
  96
  97 -       return mmc_suspend_host(mmc, state);
  98 +       ret = mmc_suspend_host(mmc, state);
  99 +
 100 +       /* so that when we resume, we use any modified max rate */
 101 +       mmc->f_max = sd_max_clk;
 102 +
 103 +       return ret;
 104  }
 105
 106  int glamo_mci_resume(struct platform_device *dev)
 107 --
 108 1.5.6.3
 109