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

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Date:   Thu, 10 Jan 2019 02:10:44 +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

> > I just looked at your regmap code and you use 3 regmap pointers for
> specific 8-bit, 16-bit, and 32-bit accesses.  The switch access is always 8-bit.  It
> has automatic register increment so that you can access arbitrary length of
> registers.  The use of 16-bit and 32-bit accesses makes access efficient if it
> makes sense.
> 
> Right, that's what happens here.
> 
> > Most older switches define registers in 8-bit.  Exceptions are the default
> VID and indirect access.
> >
> > A specific switch mostly defines registers in 16-bit because it shares the
> core design with an Ethernet controller.
> >
> > KSZ9477 is the newer designed switch and it gets some designs from older
> switches and that is why it has a mix of 8-bit, 16-bit, and 32-bit register
> definitions.
> 
> Right, that's quite horrible.
> 
> > In my code I just use regmap_bulk_read and regmap_bulk_write and still
> use the old spi access functions for specific 8-bit, 16-bit, and 32-bit accesses.
> 
> Let's not mix regmap and non-regmap accesses, that'd be a mess. Let's
> stick to one, regmap.
> 
> > We can combine the logic of ksz_spi_read8 and others into ksz_read8 and
> so they can be used for both SPI and I2C accesses.
> 
> You can just use regmap_*() accessors and regmap will deal with i2c/spi
> abstraction for you, that's the idea.
> 

What I meant is I use bulk_read as a base and modify it to access 16-bit and 32-bit instead of using regmap[1] and regmap[2].  We can keep regmap[2] for 32-bit access just for the regmap_update_bits function.

I intend to keep the 3 regmap pointers as a specific switch actually requires those specific accesses as it does not have automatic register increment.