aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/mmc
diff options
context:
space:
mode:
authorAnton Vorontsov <avorontsov@ru.mvista.com>2008-11-26 14:54:17 -0500
committerPierre Ossman <drzeus@drzeus.cx>2008-12-31 12:18:13 -0500
commit86e8286a0e48663e1e86a5884b30a6d05de2993a (patch)
tree34f9bf2dfdfa4a56edf84a96f7b7667fa195ed98 /drivers/mmc
parent0527a60c2b6bd7ab20e82cc5e488659e20eaaacd (diff)
mmc: Add mmc_vddrange_to_ocrmask() helper function
This function sets the OCR mask bits according to provided voltage ranges. Will be used by the mmc_spi OpenFirmware bindings. Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com> Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Diffstat (limited to 'drivers/mmc')
-rw-r--r--drivers/mmc/core/core.c75
1 files changed, 75 insertions, 0 deletions
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index f7284b905eb3..5f288aeeb721 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -20,6 +20,7 @@
20#include <linux/err.h> 20#include <linux/err.h>
21#include <linux/leds.h> 21#include <linux/leds.h>
22#include <linux/scatterlist.h> 22#include <linux/scatterlist.h>
23#include <linux/log2.h>
23 24
24#include <linux/mmc/card.h> 25#include <linux/mmc/card.h>
25#include <linux/mmc/host.h> 26#include <linux/mmc/host.h>
@@ -448,6 +449,80 @@ void mmc_set_bus_width(struct mmc_host *host, unsigned int width)
448 mmc_set_ios(host); 449 mmc_set_ios(host);
449} 450}
450 451
452/**
453 * mmc_vdd_to_ocrbitnum - Convert a voltage to the OCR bit number
454 * @vdd: voltage (mV)
455 * @low_bits: prefer low bits in boundary cases
456 *
457 * This function returns the OCR bit number according to the provided @vdd
458 * value. If conversion is not possible a negative errno value returned.
459 *
460 * Depending on the @low_bits flag the function prefers low or high OCR bits
461 * on boundary voltages. For example,
462 * with @low_bits = true, 3300 mV translates to ilog2(MMC_VDD_32_33);
463 * with @low_bits = false, 3300 mV translates to ilog2(MMC_VDD_33_34);
464 *
465 * Any value in the [1951:1999] range translates to the ilog2(MMC_VDD_20_21).
466 */
467static int mmc_vdd_to_ocrbitnum(int vdd, bool low_bits)
468{
469 const int max_bit = ilog2(MMC_VDD_35_36);
470 int bit;
471
472 if (vdd < 1650 || vdd > 3600)
473 return -EINVAL;
474
475 if (vdd >= 1650 && vdd <= 1950)
476 return ilog2(MMC_VDD_165_195);
477
478 if (low_bits)
479 vdd -= 1;
480
481 /* Base 2000 mV, step 100 mV, bit's base 8. */
482 bit = (vdd - 2000) / 100 + 8;
483 if (bit > max_bit)
484 return max_bit;
485 return bit;
486}
487
488/**
489 * mmc_vddrange_to_ocrmask - Convert a voltage range to the OCR mask
490 * @vdd_min: minimum voltage value (mV)
491 * @vdd_max: maximum voltage value (mV)
492 *
493 * This function returns the OCR mask bits according to the provided @vdd_min
494 * and @vdd_max values. If conversion is not possible the function returns 0.
495 *
496 * Notes wrt boundary cases:
497 * This function sets the OCR bits for all boundary voltages, for example
498 * [3300:3400] range is translated to MMC_VDD_32_33 | MMC_VDD_33_34 |
499 * MMC_VDD_34_35 mask.
500 */
501u32 mmc_vddrange_to_ocrmask(int vdd_min, int vdd_max)
502{
503 u32 mask = 0;
504
505 if (vdd_max < vdd_min)
506 return 0;
507
508 /* Prefer high bits for the boundary vdd_max values. */
509 vdd_max = mmc_vdd_to_ocrbitnum(vdd_max, false);
510 if (vdd_max < 0)
511 return 0;
512
513 /* Prefer low bits for the boundary vdd_min values. */
514 vdd_min = mmc_vdd_to_ocrbitnum(vdd_min, true);
515 if (vdd_min < 0)
516 return 0;
517
518 /* Fill the mask, from max bit to min bit. */
519 while (vdd_max >= vdd_min)
520 mask |= 1 << vdd_max--;
521
522 return mask;
523}
524EXPORT_SYMBOL(mmc_vddrange_to_ocrmask);
525
451/* 526/*
452 * Mask off any voltages we don't support and select 527 * Mask off any voltages we don't support and select
453 * the lowest voltage 528 * the lowest voltage