Re: [PATCH] Hisilicon LPC driver

[Rongrong Zou <zourongrong@huawei.com>]

在 2015/11/30 21:19, Arnd Bergmann 写道:
> On Monday 30 November 2015 21:07:17 Rongrong Zou wrote:
>> This is the Low Pin Count driver for Hisilicon Hi1610 SoC. It is used
>> for LPC master accessing LPC slave device.
>>
>> We only implement I/O read and I/O write here, and the 2 interfaces are
>> exported for uart driver and ipmi_si driver.
>>
>> Signed-off-by: Rongrong Zou <zourongrong@gmail.com>
>> Signed-off-by: lijianhua <Jueying0518@gmail.com>
>> ---
>>   .../bindings/misc/hisilicon,low-pin-count.txt      |  11 +
>>   MAINTAINERS                                        |   5 +
>>   drivers/misc/Kconfig                               |   7 +
>>   drivers/misc/Makefile                              |   1 +
>>   drivers/misc/hisi_lpc.c                            | 292 +++++++++++++++++++++
>>   include/linux/hisi_lpc.h                           |  83 ++++++
>>   6 files changed, 399 insertions(+)
>
> This should not be a misc driver.

I an not sure which subsystem to place, do you have any sugguestion?
>
>>   create mode 100644 Documentation/devicetree/bindings/misc/hisilicon,low-pin-count.txt
>>   create mode 100644 drivers/misc/hisi_lpc.c
>>   create mode 100644 include/linux/hisi_lpc.h
>> diff --git a/Documentation/devicetree/bindings/misc/hisilicon,low-pin-count.txt b/Documentation/devicetree/bindings/misc/hisilicon,low-pin-count.txt
>> new file mode 100644
>> index 0000000..05c1e19
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/misc/hisilicon,low-pin-count.txt
>> @@ -0,0 +1,11 @@
>> +Hisilicon Low Pin Count bus
>> +
>> +Required properties
>> +- compatible: "hisilicon,low-pin-count"
>> +- reg specifies low pin count address range
>> +
>> +Example:
>> +	lpc_0: lpc@a01b0000 {
>> +		compatible = "hisilicon,low-pin-count";
>> +		ret = <0x0 0xa01b0000, 0x0, 0x10000>;
>> +	};
>
> The name is too generic, unless you can guarantee that Hisilicon has never
> before made another implementation of an LPC interface, and never will
> again.

OK, I will fix it.

>
> I think you should create a child address space here using a
> '#address-cells' and '#size-cells'.

There are some mistake,it should be wrote like:
reg = <0x0 0xa01b0000 0x0 0x10000>;
>
>> +#define LPC_REG_READ(reg, result) ((result) = readl(reg))
>> +
>> +#define LPC_REG_WRITE(reg, data)   writel((data), (reg))
>
> Remove the obfuscation here.

OK
>
>> +struct hs_lpc_dev *lpc_dev;
>
> Avoid global data structures.
>
OK

>> +	LPC_REG_WRITE(lpc_dev->regs + HS_LPC_REG_IRQ_ST, HS_LPC_IRQ_CLEAR);
>> +	retry = 0;
>> +	while (0 == (LPC_REG_READ(lpc_dev->regs + HS_LPC_REG_OP_STATUS,
>> +		lpc_op_state_value) & HS_LPC_STATUS_DILE)) {
>> +		udelay(1);
>> +		retry++;
>> +		if (retry >= 10000) {
>> +			dev_err(lpc_dev->dev, "lpc W, wait idle time out\n");
>> +			return -ETIME;
>> +		}
>> +	}
>
> Better release the spinlock here and call a sleeping function for the wait.
> If the timeout is 10ms, you definitely don't want to keep interrupts disabled
> the whole time.
>
> If you can't find a good way to retry after getting the lock back, maybe
> use a mutex here that you can keep locked the whole time.
>

The interface "lpc_io_read_byte" may be called in IRQ context by UART driver,
and in process context by ipmi driver.

>> +void  lpc_io_write_byte(u8 value, unsigned long addr)
>> +{
>> +	unsigned long flags;
>> +	int ret;
>> +
>> +	if (!lpc_dev) {
>> +		pr_err("device is not register\n!");
>> +		return;
>> +	}
>> +	spin_lock_irqsave(&lpc_dev->lock, flags);
>> +	ret = lpc_master_write(HS_LPC_CMD_SAMEADDR_SING, HS_LPC_CMD_TYPE_IO,
>> +				 addr, &value, 1);
>> +	spin_unlock_irqrestore(&lpc_dev->lock, flags);
>> +}
>> +EXPORT_SYMBOL(lpc_io_write_byte);
>
> Using your own accessor functions sounds wrong here. What you have
> is essentially a PCI I/O space, right? As much as we all hate I/O
> space (in particular the kind that is not memory mapped), I think this
> should be hooked up to the generic inb/outb functions to allow
> all the generic device drivers to work.

It is not a PCI I/O space, although we want access it like IO space.
Could you explain how to hook up to the generic inb/outb functions.

>
>> diff --git a/include/linux/hisi_lpc.h b/include/linux/hisi_lpc.h
>> new file mode 100644
>> index 0000000..4cf93ee
>> --- /dev/null
>> +++ b/include/linux/hisi_lpc.h
>
> Don't do a global header here, just move it into the main file.
>
Because in previous design, the uart driver should call lpc_io_write_byte
and lpc_io_write_byte. the header file must be included in uart_driver.c to
access its exported interface.

> 	Arnd
>
> .
>
Thanks for your comment.

Rongrong