netdev - RE: [RFT][PATCH V2 09/10] net: dsa: microchip: Factor out regmap config generation into common header

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Date:   Wed, 9 Jan 2019 19:08:29 +0000
From:   <Tristram.Ha@...rochip.com>
To:     <marex@...x.de>
CC:     <f.fainelli@...il.com>, <andrew@...n.ch>,
        <Woojung.Huh@...rochip.com>, <netdev@...r.kernel.org>,
        <UNGLinuxDriver@...rochip.com>
Subject: RE: [RFT][PATCH V2 09/10] net: dsa: microchip: Factor out regmap
 config generation into common header

> >>> +	{								\
> >>> +		.val_bits = (width),					\
> >>> +		.reg_stride = (width) / 8,				\
> >>> +		.reg_bits = (regbits) + (regalign),			\
> >>> +		.pad_bits = (regpad),					\
> >>> +		.max_register = 0xF00,					\
> >>> +		.cache_type = REGCACHE_NONE,
> >>> 	\
> >>> +		.read_flag_mask =					\
> >>> +			KSZ_SPI_OP_FLAG_MASK(KSZ_SPI_OP_RD, regbits,
> >>> regpad), \
> >>> +		.write_flag_mask =					\
> >>> +			KSZ_SPI_OP_FLAG_MASK(KSZ_SPI_OP_WR, regbits,
> >>> regpad), \
> >>> +		.reg_format_endian = REGMAP_ENDIAN_BIG,
> >>> 	\
> >>> +		.val_format_endian = REGMAP_ENDIAN_BIG
> >>> 	\
> >>> +	}
> >>
> >> max_registers for KSZ9477 should be 0x8000.
> >>
> >> I found that the SPI access works with these settings:
> >> reg_bits = 32 - 5, val_bits = 8, pad_bits = 5, read_flag_mask =
> KS_SPIOP_RD << 5.
> >
> > This is wrong, val_bits must match the register width (8 for 8bit
> > regmap, 16 for 16bit regmap etc). Anyway, can you prepare a short diff
> > to give me an idea what needs to be changed ?
> >
> 
> Bump ?
> 

This is the regmap_config I used in Linux 4.9:

	.reg_bits		= SPI_REGMAP_REG,
	.val_bits		= SPI_REGMAP_VAL,
	.pad_bits		= SPI_REGMAP_PAD,
	.read_flag_mask	= KS_SPIOP_RD << SPI_REGMAP_MASK_S,
	.write_flag_mask	= KS_SPIOP_WR << SPI_REGMAP_MASK_S,
	.reg_format_endian	= REGMAP_ENDIAN_BIG,
	.val_format_endian	= REGMAP_ENDIAN_BIG,

For KSZ9477:

SPI_CMD_LEN		4
SPI_REGMAP_PAD	SPI_TURNAROUND_SHIFT
SPI_REGMAP_VAL	8
SPI_REGMAP_REG	\
	(SPI_CMD_LEN * SPI_REGMAP_VAL - SPI_TURNAROUND_SHIFT)
SPI_REGMAP_MASK_S	\
	(SPI_ADDR_SHIFT + SPI_TURNAROUND_SHIFT - \
	(SPI_CMD_LEN * SPI_REGMAP_VAL - 8))

For KSZ8795:

SPI_CMD_LEN		2
SPI_REGMAP_PAD	SPI_TURNAROUND_S
SPI_REGMAP_VAL	8
SPI_REGMAP_REG	\
	(SPI_CMD_LEN * SPI_REGMAP_VAL - SPI_TURNAROUND_S)
SPI_REGMAP_MASK_S	\
	(SPI_ADDR_S + SPI_TURNAROUND_S - \
	(SPI_CMD_LEN * SPI_REGMAP_VAL - 8))

So the differences between KSZ9477 and KSZ8795 are SPI_CMD_LEN, SPI_ADDR_S, and SPI_TURNAROUND_S.

KSZ9477:

.reg_bits = 32 - 5 = 27
.val_bits = 8
.pad_bits = 5
.read_flag_mask = KS_SPIOP_RD << 5,

KSZ8795:

.reg_bits = 16 - 1 = 15
.val_bits = 8
.pad_bits = 1
.read_flag_mask = KS_SPIOP_RD << 5,

The regmap.c code uses reg_bits + reg_shift (which comes from pad_bits) to decide whether the register space is 16-bit or 32-bit.  The value space is always 8-bit.

The shift for _flag_mask turns out to be the same for both KSZ9477 and KSZ8795.