Subject: [PATCH DRAFT 2/2] drivers: serial: PL011: [DRAFT] implement register diverson for ZTE UART

From: [email-masked] (Andre Przywara)
Date: Tue, 3 Nov 2015 13:57:45 +0000

Hi Russell,

On 03/11/15 13:46, Russell King - ARM Linux wrote:
> On Mon, Nov 02, 2015 at 12:24:02PM +0000, Andre Przywara wrote:
>> +int reg_table_zte[] = {
>> +	[UART01x_DR]	= ZX_UART01x_DR,
> 
> No entry for RSR, so the value will be zero.  That means when we read
> the RSR, we'll be reading the register at offset 0.  Maybe that's
> intentional, maybe it isn't, but it's totally screwy.

Well, as the subject says: it's a draft. And I scanned the file to see
which registers are actually accessed and only entered those into the
array. RSR is not among them. But I agree that we should eventually
enter identity mappings for all PL011 registers in existence to cover
future extensions to the driver. If there would be a clever way to
differentiate uninitialised entries from "0" we could fall back to
identify mapping upon detecting an unused index and only have the
differing registers in the code.

Cheers,
Andre.

> Someone needs to document what the register layout for the ZTE UART
> is.  Better still, point to where the spec can be found.
> 
>> +	[UART011_LCRH]	= ZX_UART011_LCRH_TX,
>> +	[UART011_CR]	= ZX_UART011_CR,
>> +	[UART01x_FR]	= ZX_UART01x_FR,
>> +	[UART011_ICR]	= ZX_UART011_ICR,
>> +	[UART011_IBRD]	= UART011_IBRD,
>> +	[UART011_FBRD]	= UART011_FBRD,
>> +	[UART011_IFLS]	= ZX_UART011_IFLS,
>> +	[UART011_IMSC]	= ZX_UART011_IMSC,
>> +	[UART011_RIS]	= ZX_UART011_RIS,
>> +	[UART011_MIS]	= ZX_UART011_MIS,
>> +	[UART011_DMACR]	= ZX_UART011_DMACR,
>> +};
>>  static unsigned int pl011_read(struct uart_amba_port *uap, int offset)
>>  {
>> +#ifdef CONFIG_SOC_ZX296702
>> +	if (uap->vendor->reg_table)
>> +		offset = uap->vendor->reg_table[offset];
>> +#endif
>>  	return readw(uap->port.membase + offset);
>>  }
>>  
>>  static void pl011_write(struct uart_amba_port *uap, int val, int offset)
>>  {
>> +#ifdef CONFIG_SOC_ZX296702
>> +	if (uap->vendor->reg_table)
>> +		offset = uap->vendor->reg_table[offset];
>> +#endif
>>  	writew(val, uap->port.membase + offset);
>>  }
>>  
>> diff --git a/include/linux/amba/serial.h b/include/linux/amba/serial.h
>> index 0ddb5c0..1c71b83 100644
>> --- a/include/linux/amba/serial.h
>> +++ b/include/linux/amba/serial.h
>> @@ -31,6 +31,7 @@
>>   *  UART Register Offsets.
>>   */
>>  #define UART01x_DR		0x00	/* Data read or written from the interface. */
>> +#define ZX_UART01x_DR		0x04	/* Different offset in the ZTE UART. */
>>  #define UART01x_RSR		0x04	/* Receive status register (Read). */
>>  #define UART01x_ECR		0x04	/* Error clear register (Write). */
>>  #define UART010_LCRH		0x08	/* Line control register, high byte. */
>> @@ -39,6 +40,7 @@
>>  #define ST_UART011_TIMEOUT	0x0C    /* Timeout period register. */
>>  #define UART010_LCRL		0x10	/* Line control register, low byte. */
>>  #define UART010_CR		0x14	/* Control register. */
>> +#define ZX_UART01x_FR		0x14	/* Different offset in the ZTE UART. */
>>  #define UART01x_FR		0x18	/* Flag register (Read only). */
>>  #define UART010_IIR		0x1C	/* Interrupt identification register (Read). */
>>  #define UART010_ICR		0x1C	/* Interrupt clear register (Write). */
>> @@ -48,14 +50,22 @@
>>  #define UART011_FBRD		0x28	/* Fractional baud rate divisor register. */
>>  #define UART011_LCRH		0x2c	/* Line control register. */
>>  #define ST_UART011_LCRH_TX	0x2c    /* Tx Line control register. */
>> +#define ZX_UART011_LCRH_TX	0x30    /* Different offset in the ZTE UART. */
>>  #define UART011_CR		0x30	/* Control register. */
>>  #define UART011_IFLS		0x34	/* Interrupt fifo level select. */
>> +#define ZX_UART011_CR		0x34	/* Different offset in the ZTE UART. */
>> +#define ZX_UART011_IFLS		0x38	/* Different offset in the ZTE UART. */
>>  #define UART011_IMSC		0x38	/* Interrupt mask. */
>>  #define UART011_RIS		0x3c	/* Raw interrupt status. */
>>  #define UART011_MIS		0x40	/* Masked interrupt status. */
>> +#define ZX_UART011_IMSC		0x40	/* Different offset in the ZTE UART. */
>>  #define UART011_ICR		0x44	/* Interrupt clear register. */
>> +#define ZX_UART011_RIS		0x44	/* Different offset in the ZTE UART. */
>>  #define UART011_DMACR		0x48	/* DMA control register. */
>> +#define ZX_UART011_MIS		0x48	/* Different offset in the ZTE UART. */
>> +#define ZX_UART011_ICR		0x4c	/* Different offset in the ZTE UART. */
>>  #define ST_UART011_XFCR		0x50	/* XON/XOFF control register. */
>> +#define ZX_UART011_DMACR	0x50	/* Different offset in the ZTE UART. */
>>  #define ST_UART011_XON1		0x54	/* XON1 register. */
>>  #define ST_UART011_XON2		0x58	/* XON2 register. */
>>  #define ST_UART011_XOFF1	0x5C	/* XON1 register. */
>> -- 
>> 2.5.1
>>
>