Re: [PATCH v14 6/9] HISI LPC: Support the LPC host on Hip06/Hip07 with DT bindings

[Andy Shevchenko]

On Mon, Feb 19, 2018 at 7:48 PM, John Garry <john.garry@xxxxxxxxxx> wrote:
> From: Zhichang Yuan <yuanzhichang@xxxxxxxxxxxxx>
>
> The low-pin-count(LPC) interface of Hip06/Hip07 accesses the peripherals in
> I/O port addresses. This patch implements the LPC host controller driver
> which perform the I/O operations on the underlying hardware.
> We don't want to touch those existing peripherals' driver, such as ipmi-bt.
> So this driver applies the indirect-IO introduced in the previous patch
> after registering an indirect-IO node to the indirect-IO devices list which
> will be searched in the I/O accessors to retrieve the host-local I/O port.
>
> The driver config is set as a bool instead of a trisate. The reason
> here is that, by the very nature of the driver providing a logical
> PIO range, it does not make sense to have this driver as a loadable
> module. Another more specific reason is that the Huawei D03 board
> which includes hip06 SoC requires the LPC bus for UART console, so
> should be built in.

> +config HISILICON_LPC
> +       bool "Support for ISA I/O space on Hisilicon hip06/7"
> +       depends on (ARM64 && (ARCH_HISI || COMPILE_TEST))

Redundant parens.

> +       select INDIRECT_PIO
> +       help
> +         Driver needed for some legacy ISA devices attached to Low-Pin-Count
> +         on Hisilicon hip06/7 SoC.



> +#if LPC_MAX_DULEN > LPC_MAX_BURST
> +#error "LPC.. MAX_DULEN must be not bigger than MAX_OPCNT!"
> +#endif

But here you can easily avoid an #error, by making them equal, just
issue a warning instead.

> +#if LPC_MAX_BURST % LPC_MAX_DULEN
> +#error "LPC.. LPC_MAX_BURST must be multiple of LPC_MAX_DULEN!"
> +#endif

Is it like this, or also should be power of two?

> +/* The command register fields */
> +#define LPC_CMD_SAMEADDR       0x08
> +#define LPC_CMD_TYPE_IO                0x00

> +#define LPC_CMD_WRITE          0x01
> +#define LPC_CMD_READ           0x00
> +/* the bit attribute is W1C. 1 represents OK. */
> +#define LPC_STAT_BYIRQ         0x02

BIT() ?

> +#define LPC_STATUS_IDLE                0x01
> +#define LPC_OP_FINISHED                0x02
> +
> +#define LPC_START_WORK         0x01

Ditto?

> +static inline int wait_lpc_idle(unsigned char *mbase,
> +                               unsigned int waitcnt) {
> +       u32 opstatus;
> +
> +       while (waitcnt--) {
> +               ndelay(LPC_NSEC_PERWAIT);
> +               opstatus = readl(mbase + LPC_REG_OP_STATUS);
> +               if (opstatus & LPC_STATUS_IDLE)
> +                       return (opstatus & LPC_OP_FINISHED) ? 0 : (-EIO);
> +       }
> +       return -ETIME;

Personally I prefer timeout loops in a do {} while (--count) style.

> +}

> +static int
> +hisi_lpc_target_in(struct hisi_lpc_dev *lpcdev, struct lpc_cycle_para *para,
> +                 unsigned long addr, unsigned char *buf,
> +                 unsigned long opcnt)
> +{
> +       unsigned int cmd_word;
> +       unsigned int waitcnt;
> +       unsigned long flags;
> +       int ret;
> +
> +       if (!buf || !opcnt || !para || !para->csize || !lpcdev)
> +               return -EINVAL;

> +
> +       cmd_word = LPC_CMD_TYPE_IO | LPC_CMD_READ;
> +       waitcnt = LPC_PEROP_WAITCNT;
> +       if (!(para->opflags & FG_INCRADDR_LPC)) {
> +               cmd_word |= LPC_CMD_SAMEADDR;
> +               waitcnt = LPC_MAX_WAITCNT;
> +       }
> +

> +       ret = 0;
> +

Sounds redundant.

> +       /* whole operation must be atomic */
> +       spin_lock_irqsave(&lpcdev->cycle_lock, flags);
> +
> +       writel_relaxed(opcnt, lpcdev->membase + LPC_REG_OP_LEN);
> +
> +       writel_relaxed(cmd_word, lpcdev->membase + LPC_REG_CMD);
> +
> +       writel_relaxed(addr, lpcdev->membase + LPC_REG_ADDR);
> +
> +       writel(LPC_START_WORK, lpcdev->membase + LPC_REG_START);
> +
> +       /* whether the operation is finished */
> +       ret = wait_lpc_idle(lpcdev->membase, waitcnt);

> +       if (!ret) {

I would rather go with usual pattern
if (ret) {
 ...
 return ret;
}


> +               for (; opcnt; opcnt--, buf++)
> +                       *buf = readb(lpcdev->membase + LPC_REG_RDATA);

Looks like a do {} while (slightly better for my opinion).

do {
              *buf++ = readb(lpcdev->membase + LPC_REG_RDATA);
} while (--opcnt);

> +       }
> +
> +       spin_unlock_irqrestore(&lpcdev->cycle_lock, flags);
> +
> +       return ret;
> +}

> +       for (; opcnt; buf++, opcnt--)
> +               writeb(*buf, lpcdev->membase + LPC_REG_WDATA);

Ditto.

> +static u32 hisi_lpc_comm_in(void *hostdata, unsigned long pio, size_t dwidth)

> +       if (!lpcdev || !dwidth || dwidth > LPC_MAX_DULEN)
> +               return -1;

~0 ?

> +       if (ret)
> +               return -1;

Ditto.

> +       do {
> +               int ret;
> +
> +               ret = hisi_lpc_target_in(lpcdev, &iopara, addr,
> +                                       buf, dwidth);
> +               if (ret)
> +                       return ret;
> +               buf += dwidth;

> +               count--;
> +       } while (count);

} while (--count);

> +       do {
> +               if (hisi_lpc_target_out(lpcdev, &iopara, addr, buf,
> +                                               dwidth))
> +                       break;
> +               buf += dwidth;
> +               count--;
> +       } while (count);

Ditto.

> +static int hisi_lpc_probe(struct platform_device *pdev)
> +{
> +       struct device *dev = &pdev->dev;
> +       struct acpi_device *acpi_device = ACPI_COMPANION(dev);
> +       struct logic_pio_hwaddr *range;
> +       struct hisi_lpc_dev *lpcdev;
> +       struct resource *res;

> +       int ret = 0;

Redundant assignment.

> +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);

> +       if (!res)
> +               return -ENODEV;

Redundant.

> +
> +       lpcdev->membase = devm_ioremap_resource(dev, res);
> +       if (IS_ERR(lpcdev->membase)) {

> +               dev_err(dev, "remap failed\n");

Redundant.

> +               return PTR_ERR(lpcdev->membase);
> +       }

> +       /* register the LPC host PIO resources */

> +       if (!acpi_device)
> +               ret = of_platform_populate(dev->of_node, NULL, NULL, dev);

> +       if (ret) {

> +               dev_err(dev, "populate children failed (%d)\n", ret);

JFYI: ret is printed by device core if ->probe() fails.

> +               return ret;
> +       }

This condition should go under if (!acpi_device) case.

-- 
With Best Regards,
Andy Shevchenko