Commit f6f1f8e6 authored by Aswath Govindraju's avatar Aswath Govindraju Committed by Greg Kroah-Hartman
Browse files

misc: eeprom_93xx46: Add quirk to support Microchip 93LC46B eeprom 

A dummy zero bit is sent preceding the data during a read transfer by the
Microchip 93LC46B eeprom (section 2.7 of[1]). This results in right shift
of data during a read. In order to ignore this bit a quirk can be added to
send an extra zero bit after the read address.

Add a quirk to ignore the zero bit sent before data by adding a zero bit
after the read address.

[1] - https://www.mouser.com/datasheet/2/268/20001749K-277859.pdf



Signed-off-by: default avatarAswath Govindraju <a-govindraju@ti.com>
Link: https://lore.kernel.org/r/20210105105817.17644-3-a-govindraju@ti.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 68058229

drivers/misc/eeprom/eeprom_93xx46.c

+15 −0
Original line number Diff line number Diff line
@@ -35,6 +35,10 @@ static const struct eeprom_93xx46_devtype_data atmel_at93c46d_data = { 
		  EEPROM_93XX46_QUIRK_INSTRUCTION_LENGTH,

};



static const struct eeprom_93xx46_devtype_data microchip_93lc46b_data = {

	.quirks = EEPROM_93XX46_QUIRK_EXTRA_READ_CYCLE,

};



struct eeprom_93xx46_dev {

	struct spi_device *spi;

	struct eeprom_93xx46_platform_data *pdata;
@@ -55,6 +59,11 @@ static inline bool has_quirk_instruction_length(struct eeprom_93xx46_dev *edev) 
	return edev->pdata->quirks & EEPROM_93XX46_QUIRK_INSTRUCTION_LENGTH;

}



static inline bool has_quirk_extra_read_cycle(struct eeprom_93xx46_dev *edev)

{

	return edev->pdata->quirks & EEPROM_93XX46_QUIRK_EXTRA_READ_CYCLE;

}



static int eeprom_93xx46_read(void *priv, unsigned int off,

			      void *val, size_t count)

{
@@ -96,6 +105,11 @@ static int eeprom_93xx46_read(void *priv, unsigned int off, 
		dev_dbg(&edev->spi->dev, "read cmd 0x%x, %d Hz\n",

			cmd_addr, edev->spi->max_speed_hz);



		if (has_quirk_extra_read_cycle(edev)) {

			cmd_addr <<= 1;

			bits += 1;

		}



		spi_message_init(&m);



		t[0].tx_buf = (char *)&cmd_addr;
@@ -363,6 +377,7 @@ static void select_deassert(void *context) 
static const struct of_device_id eeprom_93xx46_of_table[] = {

	{ .compatible = "eeprom-93xx46", },

	{ .compatible = "atmel,at93c46d", .data = &atmel_at93c46d_data, },

	{ .compatible = "microchip,93lc46b", .data = &microchip_93lc46b_data, },

	{}

};

MODULE_DEVICE_TABLE(of, eeprom_93xx46_of_table);

include/linux/eeprom_93xx46.h

+2 −0
Original line number Diff line number Diff line
@@ -16,6 +16,8 @@ struct eeprom_93xx46_platform_data { 
#define EEPROM_93XX46_QUIRK_SINGLE_WORD_READ		(1 << 0)

/* Instructions such as EWEN are (addrlen + 2) in length. */

#define EEPROM_93XX46_QUIRK_INSTRUCTION_LENGTH		(1 << 1)

/* Add extra cycle after address during a read */

#define EEPROM_93XX46_QUIRK_EXTRA_READ_CYCLE		BIT(2)



	/*

	 * optional hooks to control additional logic