[U-Boot] [PATCH v2] spi: kirkwood_spi: implement workaround for FE-9144572

[Jagan Teki]

On Tue, Oct 17, 2017 at 4:15 AM, Chris Packham <judge.packham at gmail.com> wrote:
> On Tue, Oct 17, 2017 at 10:46 AM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
>> On Tue, Oct 17, 2017 at 3:07 AM, Chris Packham <judge.packham at gmail.com> wrote:
>>> Erratum NO. FE-9144572: The device SPI interface supports frequencies of
>>> up to 50 MHz.  However, due to this erratum, when the device core clock
>>> is 250 MHz and the SPI interfaces is configured for 50MHz SPI clock and
>>> CPOL=CPHA=1 there might occur data corruption on reads from the SPI
>>> device.
>>>
>>> Implement the workaround by setting the TMISO_SAMPLE value to 0x2
>>> in the timing1 register.
>>>
>>> Signed-off-by: Chris Packham <judge.packham at gmail.com>
>>> Reviewed-by: Stefan Roese <sr at denx.de>
>>> ---
>>> I've based this as much as I can on the equivalent implementation in the
>>> Linux kernel[1], but there are differences in the u-boot spi
>>> infrastructure that means I can't be as specific when qualifying whether
>>> the workaround is needed.
>>>
>>> [1] - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/spi/spi-orion.c#n248
>>>
>>> Changes in v2:
>>> - collect reviewed-by from Stefan
>>> - remove mvebu_spi_type
>>> - describe errata above mvebu_spi_50mhz_ac_timing_erratum
>>>
>>>  arch/arm/include/asm/arch-mvebu/spi.h |  6 ++++
>>>  drivers/spi/kirkwood_spi.c            | 61 +++++++++++++++++++++++++++++++++--
>>>  2 files changed, 64 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/arch/arm/include/asm/arch-mvebu/spi.h b/arch/arm/include/asm/arch-mvebu/spi.h
>>> index 3545aed17347..1de510ea6da9 100644
>>> --- a/arch/arm/include/asm/arch-mvebu/spi.h
>>> +++ b/arch/arm/include/asm/arch-mvebu/spi.h
>>> @@ -57,6 +57,12 @@ struct kwspi_registers {
>>>  #define KWSPI_TXLSBF           (1 << 13)
>>>  #define KWSPI_RXLSBF           (1 << 14)
>>>
>>> +/* Timing Parameters 1 Register */
>>> +#define KW_SPI_TMISO_SAMPLE_OFFSET     6
>>> +#define KW_SPI_TMISO_SAMPLE_MASK       (0x3 << KW_SPI_TMISO_SAMPLE_OFFSET)
>>> +#define KW_SPI_TMISO_SAMPLE_1          (1 << KW_SPI_TMISO_SAMPLE_OFFSET)
>>> +#define KW_SPI_TMISO_SAMPLE_2          (2 << KW_SPI_TMISO_SAMPLE_OFFSET)
>>> +
>>>  #define KWSPI_IRQUNMASK                1 /* unmask SPI interrupt */
>>>  #define KWSPI_IRQMASK          0 /* mask SPI interrupt */
>>>  #define KWSPI_SMEMRDIRQ                1 /* SerMem data xfer ready irq */
>>> diff --git a/drivers/spi/kirkwood_spi.c b/drivers/spi/kirkwood_spi.c
>>> index 0c6bd295cde9..5b1ac0eed634 100644
>>> --- a/drivers/spi/kirkwood_spi.c
>>> +++ b/drivers/spi/kirkwood_spi.c
>>> @@ -243,6 +243,10 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
>>>
>>>  /* Here now the DM part */
>>>
>>> +struct mvebu_spi_dev {
>>> +       bool                    is_errata_50mhz_ac;
>>> +};
>>> +
>>>  struct mvebu_spi_platdata {
>>>         struct kwspi_registers *spireg;
>>>  };
>>> @@ -269,10 +273,38 @@ static int mvebu_spi_set_speed(struct udevice *bus, uint hz)
>>>         return 0;
>>>  }
>>>
>>> +/*
>>> + * FE-9144572: The device SPI interface supports frequencies of up to 50 MHz.
>>> + * However, due to this erratum, when the device core clock is 250 MHz and the
>>> + * SPI interfaces is configured for 50MHz SPI clock and CPOL=CPHA=1 there might
>>> + * occur data corruption on reads from the SPI device.
>>> + *
>>> + * Workaround: Set the TMISO_SAMPLE value to 0x2 in the SPI Timing Parameters 1
>>> + * register
>>> + */

Move the comments on function definition like Linux and make sure
comments should be similar.

>>> +static void mvebu_spi_50mhz_ac_timing_erratum(struct udevice *bus, uint mode)
>>> +{
>>> +       struct mvebu_spi_platdata *plat = dev_get_platdata(bus);
>>> +       struct kwspi_registers *reg = plat->spireg;
>>> +       u32 data = readl(&reg->timing1);
>>> +
>>> +       data &= ~KW_SPI_TMISO_SAMPLE_MASK;
>>> +
>>> +       if (CONFIG_SYS_TCLK == 250000000 &&
>>> +           mode & SPI_CPOL &&
>>> +           mode & SPI_CPHA)
>>> +               data |= KW_SPI_TMISO_SAMPLE_2;
>>> +       else
>>> +               data |= KW_SPI_TMISO_SAMPLE_1;
>>> +
>>> +       writel(data, &reg->timing1);
>>> +}
>>> +

Reviewed-by: Jagan Teki <jagan at openedev.com>