netdev - Re: [PATCH V3 07/10] net: dsa: microchip: Initial SPI regmap support

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Date:   Tue, 25 Jun 2019 02:59:56 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Marek Vasut <marex@...x.de>
Cc:     netdev <netdev@...r.kernel.org>, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Tristram Ha <Tristram.Ha@...rochip.com>,
        Woojung Huh <Woojung.Huh@...rochip.com>
Subject: Re: [PATCH V3 07/10] net: dsa: microchip: Initial SPI regmap support

On Tue, 25 Jun 2019 at 01:17, Marek Vasut <marex@...x.de> wrote:
>
> On 6/24/19 12:35 AM, Marek Vasut wrote:
> > Add basic SPI regmap support into the driver.
> >
> > Previous patches unconver that ksz_spi_write() is always ever called
> > with len = 1, 2 or 4. We can thus drop the if (len > SPI_TX_BUF_LEN)
> > check and we can also drop the allocation of the txbuf which is part
> > of the driver data and wastes 256 bytes for no reason. Regmap covers
> > the whole thing now.
> >
> > Signed-off-by: Marek Vasut <marex@...x.de>
> > Cc: Andrew Lunn <andrew@...n.ch>
> > Cc: Florian Fainelli <f.fainelli@...il.com>
> > Cc: Tristram Ha <Tristram.Ha@...rochip.com>
> > Cc: Woojung Huh <Woojung.Huh@...rochip.com>
>
> [...]
>
> > +#define KS_SPIOP_FLAG_MASK(opcode)           \
> > +     cpu_to_be32((opcode) << (SPI_ADDR_SHIFT + SPI_TURNAROUND_SHIFT))
>
> So the robot is complaining about this. I believe this is correct, as
> the mask should be in native endianness on the register and NOT the
> native endianness of the CPU.
>
> I think a cast would help here, e.g.:
> -       cpu_to_be32((opcode) << (SPI_ADDR_SHIFT + SPI_TURNAROUND_SHIFT))
> -       (__force unsigned long)cpu_to_be32((opcode) << (SPI_ADDR_SHIFT +
> SPI_TURNAROUND_SHIFT))
>
> Does this make sense ?
>
> > +#define KSZ_REGMAP_COMMON(width)                                     \
> > +     {                                                               \
> > +             .val_bits = (width),                                    \
> > +             .reg_stride = (width) / 8,                              \
> > +             .reg_bits = SPI_ADDR_SHIFT + SPI_ADDR_ALIGN,            \
> > +             .pad_bits = SPI_TURNAROUND_SHIFT,                       \
> > +             .max_register = BIT(SPI_ADDR_SHIFT) - 1,                \
> > +             .cache_type = REGCACHE_NONE,                            \
> > +             .read_flag_mask = KS_SPIOP_FLAG_MASK(KS_SPIOP_RD),      \
> > +             .write_flag_mask = KS_SPIOP_FLAG_MASK(KS_SPIOP_WR),     \
>
> [...]
>
> --
> Best regards,
> Marek Vasut

Hi Marek,

I saw SPI buffers and endianness and got triggered :)
Would it make sense to take a look at CONFIG_PACKING for the KSZ9477 driver?
I don't know how bad the field alignment issue is on that hardware,
but on SJA1105 it was such a disaster that I couldn't have managed it
any other way.

Regards,
-Vladimir