Commit 86e8286a authored by Anton Vorontsov's avatar Anton Vorontsov Committed by Pierre Ossman
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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: default avatarAnton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: default avatarPierre Ossman <drzeus@drzeus.cx>
parent 0527a60c
......@@ -20,6 +20,7 @@
#include <linux/err.h>
#include <linux/leds.h>
#include <linux/scatterlist.h>
#include <linux/log2.h>
#include <linux/mmc/card.h>
#include <linux/mmc/host.h>
......@@ -448,6 +449,80 @@ void mmc_set_bus_width(struct mmc_host *host, unsigned int width)
mmc_set_ios(host);
}
/**
* mmc_vdd_to_ocrbitnum - Convert a voltage to the OCR bit number
* @vdd: voltage (mV)
* @low_bits: prefer low bits in boundary cases
*
* This function returns the OCR bit number according to the provided @vdd
* value. If conversion is not possible a negative errno value returned.
*
* Depending on the @low_bits flag the function prefers low or high OCR bits
* on boundary voltages. For example,
* with @low_bits = true, 3300 mV translates to ilog2(MMC_VDD_32_33);
* with @low_bits = false, 3300 mV translates to ilog2(MMC_VDD_33_34);
*
* Any value in the [1951:1999] range translates to the ilog2(MMC_VDD_20_21).
*/
static int mmc_vdd_to_ocrbitnum(int vdd, bool low_bits)
{
const int max_bit = ilog2(MMC_VDD_35_36);
int bit;
if (vdd < 1650 || vdd > 3600)
return -EINVAL;
if (vdd >= 1650 && vdd <= 1950)
return ilog2(MMC_VDD_165_195);
if (low_bits)
vdd -= 1;
/* Base 2000 mV, step 100 mV, bit's base 8. */
bit = (vdd - 2000) / 100 + 8;
if (bit > max_bit)
return max_bit;
return bit;
}
/**
* mmc_vddrange_to_ocrmask - Convert a voltage range to the OCR mask
* @vdd_min: minimum voltage value (mV)
* @vdd_max: maximum voltage value (mV)
*
* This function returns the OCR mask bits according to the provided @vdd_min
* and @vdd_max values. If conversion is not possible the function returns 0.
*
* Notes wrt boundary cases:
* This function sets the OCR bits for all boundary voltages, for example
* [3300:3400] range is translated to MMC_VDD_32_33 | MMC_VDD_33_34 |
* MMC_VDD_34_35 mask.
*/
u32 mmc_vddrange_to_ocrmask(int vdd_min, int vdd_max)
{
u32 mask = 0;
if (vdd_max < vdd_min)
return 0;
/* Prefer high bits for the boundary vdd_max values. */
vdd_max = mmc_vdd_to_ocrbitnum(vdd_max, false);
if (vdd_max < 0)
return 0;
/* Prefer low bits for the boundary vdd_min values. */
vdd_min = mmc_vdd_to_ocrbitnum(vdd_min, true);
if (vdd_min < 0)
return 0;
/* Fill the mask, from max bit to min bit. */
while (vdd_max >= vdd_min)
mask |= 1 << vdd_max--;
return mask;
}
EXPORT_SYMBOL(mmc_vddrange_to_ocrmask);
/*
* Mask off any voltages we don't support and select
* the lowest voltage
......
......@@ -151,4 +151,6 @@ static inline void mmc_claim_host(struct mmc_host *host)
__mmc_claim_host(host, NULL);
}
extern u32 mmc_vddrange_to_ocrmask(int vdd_min, int vdd_max);
#endif
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