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

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Date:   Tue, 25 Jun 2019 14:06:04 +0200
From:   Marek Vasut <marex@...x.de>
To:     Vladimir Oltean <olteanv@...il.com>
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 6/25/19 1:59 AM, Vladimir Oltean wrote:
> 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.

How does that help me here ? All I really need is a static constant mask
for the register/flags , 32bit for KSZ9xxx and 16bit for KSZ87xx. I
don't need any dynamic stuff, luckily.

But I'm glad to see TJA1105 driver mainline :)

-- 
Best regards,
Marek Vasut