Re: [PATCH v2 2/7] serial: exar: add support for reading from Exar EEPROM

Parker Newman
2024-04-12T13:07:06Z

On Fri, 12 Apr 2024 13:36:42 +0300 (EEST)
Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:

> On Thu, 11 Apr 2024, parker@finest.io wrote:
>
> > From: Parker Newman <pnewman@connecttech.com>
> >
> > - Adds support for reading a word from the Exar EEPROM.
> > - Adds exar_write_reg/exar_read_reg for reading and writing to the UART's
> > config registers.
> >
> > Signed-off-by: Parker Newman <pnewman@connecttech.com>
> > ---
> > drivers/tty/serial/8250/8250_exar.c | 110 ++++++++++++++++++++++++++++
> > 1 file changed, 110 insertions(+)
> >
> > diff --git a/drivers/tty/serial/8250/8250_exar.c b/drivers/tty/serial/8250/8250_exar.c
> > index 4d1e07343d0b..49d690344e65 100644
> > --- a/drivers/tty/serial/8250/8250_exar.c
> > +++ b/drivers/tty/serial/8250/8250_exar.c
> > @@ -128,6 +128,16 @@
> > #define UART_EXAR_DLD 0x02 /* Divisor Fractional */
> > #define UART_EXAR_DLD_485_POLARITY 0x80 /* RS-485 Enable Signal Polarity */
> >
> > +/* EEPROM registers */
> > +#define UART_EXAR_REGB 0x8e
> > +#define UART_EXAR_REGB_EECK BIT(4)
> > +#define UART_EXAR_REGB_EECS BIT(5)
> > +#define UART_EXAR_REGB_EEDI BIT(6)
> > +#define UART_EXAR_REGB_EEDO BIT(7)
> > +#define UART_EXAR_REGB_EE_ADDR_SIZE 6
> > +#define UART_EXAR_REGB_EE_DATA_SIZE 16
> > +
> > +
>
> Extra new line.
>
> > /*
> > * IOT2040 MPIO wiring semantics:
> > *
> > @@ -195,6 +205,106 @@ struct exar8250 {
> > int line[];
> > };
> >
> > +static inline void exar_write_reg(struct exar8250 *priv,
> > + unsigned int reg, uint8_t value)
> > +{
> > + if (!priv || !priv->virt)
> > + return;
> > +
> > + writeb(value, priv->virt + reg);
> > +}
> > +
> > +static inline uint8_t exar_read_reg(struct exar8250 *priv, unsigned int reg)
> > +{
> > + if (!priv || !priv->virt)
> > + return 0;
> > +
> > + return readb(priv->virt + reg);
> > +}
> > +
> > +static inline void exar_ee_select(struct exar8250 *priv, bool enable)
> > +{
> > + uint8_t value = 0x00;
> > +
> > + if (enable)
> > + value |= UART_EXAR_REGB_EECS;
>
> You could just do:
> u8 value;
>
> value = enable ? UART_EXAR_REGB_EECS : 0;
>
> Or even:
>
> exar_write_reg(priv, UART_EXAR_REGB, enable ? UART_EXAR_REGB_EECS : 0);
> > +
> > + exar_write_reg(priv, UART_EXAR_REGB, value);
> > + udelay(2);
> > +}
> > +
> > +static inline void exar_ee_write_bit(struct exar8250 *priv, int bit)
> > +{
> > + uint8_t value = UART_EXAR_REGB_EECS;
> > +
> > + if (bit)
> > + value |= UART_EXAR_REGB_EEDI;
> > +
> > + //Clock out the bit on the i2c interface
> > + exar_write_reg(priv, UART_EXAR_REGB, value);
> > + udelay(2);
> > +
> > + value |= UART_EXAR_REGB_EECK;
> > +
> > + exar_write_reg(priv, UART_EXAR_REGB, value);
> > + udelay(2);
> > +}
> > +
> > +static inline uint8_t exar_ee_read_bit(struct exar8250 *priv)
> > +{
> > + uint8_t regb;
> > + uint8_t value = UART_EXAR_REGB_EECS;
> > +
> > + //Clock in the bit on the i2c interface
> > + exar_write_reg(priv, UART_EXAR_REGB, value);
> > + udelay(2);
> > +
> > + value |= UART_EXAR_REGB_EECK;
> > +
> > + exar_write_reg(priv, UART_EXAR_REGB, value);
> > + udelay(2);
> > +
> > + regb = exar_read_reg(priv, UART_EXAR_REGB);
> > +
> > + return (regb & UART_EXAR_REGB_EEDO ? 1 : 0);
> > +}
> > +
> > +/**
> > + * exar_ee_read() - Read a word from the EEPROM
> > + * @priv: Device's private structure
> > + * @ee_addr: Offset of EEPROM to read word from
> > + *
> > + * Read a single 16bit word from an Exar UART's EEPROM
>
> Add missing .
>
> > + *
> > + * Return: EEPROM word on success, negative error code on failure
>
> This function does not return any -Exx code as far as I can see??
>
> > + */
> > +static int exar_ee_read(struct exar8250 *priv, uint8_t ee_addr)
> > +{
> > + int i;
> > + int data = 0;
> > +
> > + exar_ee_select(priv, true);
> > +
> > + //Send read command (opcode 110)
> > + exar_ee_write_bit(priv, 1);
> > + exar_ee_write_bit(priv, 1);
> > + exar_ee_write_bit(priv, 0);
> > +
> > + //Send address to read from
> > + for (i = 1 << (UART_EXAR_REGB_EE_ADDR_SIZE - 1); i; i >>= 1)
> > + exar_ee_write_bit(priv, (ee_addr & i));
> > +
> > + //Read data 1 bit at a time
> > + for (i = 0; i <= UART_EXAR_REGB_EE_DATA_SIZE; i++) {
> > + data <<= 1;
> > + data |= exar_ee_read_bit(priv);
> > + }
> > +
> > + exar_ee_select(priv, false);
> > +
> > + return data;
> > +}
>

I will fix all of these.
Thanks,
-Parker