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Commit 86e8286a authored by Anton Vorontsov's avatar Anton Vorontsov Committed by Pierre Ossman
Browse files

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

drivers/mmc/core/core.c

+75 −0
Original line number Diff line number Diff line
@@ -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

include/linux/mmc/core.h

+2 −0
Original line number Diff line number Diff line
@@ -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