diff options
Diffstat (limited to 'target/linux/s3c24xx/patches-2.6.24/1236-add-limit-sdcard-clk-cmdline.patch.patch')
| -rw-r--r-- | target/linux/s3c24xx/patches-2.6.24/1236-add-limit-sdcard-clk-cmdline.patch.patch | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/target/linux/s3c24xx/patches-2.6.24/1236-add-limit-sdcard-clk-cmdline.patch.patch b/target/linux/s3c24xx/patches-2.6.24/1236-add-limit-sdcard-clk-cmdline.patch.patch new file mode 100644 index 0000000..01200c4 --- /dev/null +++ b/target/linux/s3c24xx/patches-2.6.24/1236-add-limit-sdcard-clk-cmdline.patch.patch @@ -0,0 +1,109 @@ +From ef2376d29e996d9d21a9e5798cb88aa73f734c83 Mon Sep 17 00:00:00 2001 +From: Andy Green <andy@openmoko.com> +Date: Thu, 17 Jul 2008 10:02:35 +0100 +Subject: [PATCH] add-limit-sdcard-clk-cmdline.patch + +This patch allows you to control the maximum clock rate that will +be selected for SD Card access, from the kernel commandline using + + glamo_mci.sd_max_clk=10000000 + +and also from + + echo 10000000 > /sys/module/glamo_mci/parameters/sd_max_clk + +although you have to suspend and resume to make the limit operational +on the actual SD_CLK line. + +Clocks that are possible are divided down from ~50MHz, so 25000000, +16666666, 12500000, 10000000, etc. With Freerunner A5 revision that +has 100R series resistors in SD Card signals, I didn't get reliable +operation above 16MHz. With A6 revision the series resistors went +down to 75R, maybe it can work at 25MHz. + +Reducing the clock rate is something to try if you find that your +SD Card is not communicating properly with the default speed. + +Signed-off-by: Andy Green <andy@openmoko.com> +--- + drivers/mfd/glamo/glamo-mci.c | 38 +++++++++++++++++++++++++++++--------- + 1 files changed, 29 insertions(+), 9 deletions(-) + +diff --git a/drivers/mfd/glamo/glamo-mci.c b/drivers/mfd/glamo/glamo-mci.c +index 350b47d..6729244 100644 +--- a/drivers/mfd/glamo/glamo-mci.c ++++ b/drivers/mfd/glamo/glamo-mci.c +@@ -40,6 +40,24 @@ static spinlock_t clock_lock; + + static void glamo_mci_send_request(struct mmc_host *mmc); + ++/* ++ * Max SD clock rate ++ * ++ * held at /(3 + 1) due to concerns of 100R recommended series resistor ++ * allows 16MHz @ 4-bit --> 8MBytes/sec raw ++ * ++ * you can override this on kernel commandline using ++ * ++ * glamo_mci.sd_max_clk=10000000 ++ * ++ * for example ++ */ ++ ++static int sd_max_clk = 50000000 / 3; ++module_param(sd_max_clk, int, 0644); ++ ++ ++ + unsigned char CRC7(u8 * pu8, int cnt) + { + u8 crc = 0; +@@ -676,9 +694,9 @@ static void glamo_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios) + (ios->power_mode == MMC_POWER_UP)) { + dev_info(&host->pdev->dev, + "powered (vdd = %d) clk: %lukHz div=%d (req: %ukHz). " +- "Bus width=%d\n",ios->vdd, +- host->real_rate / 1000, host->real_rate, +- ios->clock / 1000, ios->bus_width); ++ "Bus width=%d\n",(int)ios->vdd, ++ host->real_rate / 1000, (int)host->clk_div, ++ ios->clock / 1000, (int)ios->bus_width); + } else + dev_info(&host->pdev->dev, "glamo_mci_set_ios: power down.\n"); + +@@ -800,11 +818,7 @@ static int glamo_mci_probe(struct platform_device *pdev) + MMC_CAP_MMC_HIGHSPEED | + MMC_CAP_SD_HIGHSPEED; + mmc->f_min = host->clk_rate / 256; +- /* +- * held at /4 due to concerns of 100R recommended series resistor +- * allows 16MHz @ 4-bit --> 8MBytes/sec raw +- */ +- mmc->f_max = host->clk_rate / 3; ++ mmc->f_max = sd_max_clk; + + mmc->max_blk_count = (1 << 16) - 1; /* GLAMO_REG_MMC_RB_BLKCNT */ + mmc->max_blk_size = (1 << 12) - 1; /* GLAMO_REG_MMC_RB_BLKLEN */ +@@ -866,12 +880,18 @@ static int glamo_mci_suspend(struct platform_device *dev, pm_message_t state) + { + struct mmc_host *mmc = platform_get_drvdata(dev); + struct glamo_mci_host *host = mmc_priv(mmc); ++ int ret; + + host->suspending++; + if (host->pdata->mci_all_dependencies_resumed) + (host->pdata->mci_suspending)(dev); + +- return mmc_suspend_host(mmc, state); ++ ret = mmc_suspend_host(mmc, state); ++ ++ /* so that when we resume, we use any modified max rate */ ++ mmc->f_max = sd_max_clk; ++ ++ return ret; + } + + int glamo_mci_resume(struct platform_device *dev) +-- +1.5.6.5 + |