Re: [PATCH v1 6/9] usb: xhci: Add NVIDIA Tegra XHCI host-controller driver

[Stephen Warren]

On 06/18/2014 12:16 AM, Andrew Bresticker wrote:
> Add support for the on-chip XHCI host controller present on Tegra SoCs.
> 
> The driver is currently very basic: it loads the controller with its
> firmware, starts the controller, and is able to service messages sent
> by the controller's firmware.  The hardware supports device mode as
> well as runtime power-gating, but support for these is not yet
> implemented here.
> 
> Based on work by:
>   Ajay Gupta <ajayg@xxxxxxxxxx>
>   Bharath Yadav <byadav@xxxxxxxxxx>

> diff --git a/drivers/usb/host/Kconfig b/drivers/usb/host/Kconfig

> +config USB_XHCI_TEGRA
> +	tristate "NVIDIA Tegra XHCI support"
> +	depends on ARCH_TEGRA
> +	select PINCTRL_TEGRA_XUSB
> +	select TEGRA_XUSB_MBOX
> +	select FW_LOADER

I think at least some of those should be depends. In particular, the
mbox driver patch said:

+config TEGRA_XUSB_MBOX
+	bool "NVIDIA Tegra XUSB mailbox support"

which means the option is user-selectable. Either MBOX should be
invisible and selected here, or it should be visible with USB_XHCI_TEGRA
depending on it.

> diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c

> +#define TEGRA_XHCI_UTMI_PHYS 3
> +#define TEGRA_XHCI_HSIC_PHYS 2
> +#define TEGRA_XHCI_USB3_PHYS 2
> +#define TEGRA_XHCI_MAX_PHYS (TEGRA_XHCI_UTMI_PHYS + TEGRA_XHCI_HSIC_PHYS + \
> +			     TEGRA_XHCI_USB3_PHYS)

Do those numbers need to be synchronized with the XUSB padctrl driver at
all?

> +static u32 csb_readl(struct tegra_xhci_hcd *tegra, u32 addr)
> +{
> +	u32 page, offset;
> +
> +	page = CSB_PAGE_SELECT(addr);
> +	offset = CSB_PAGE_OFFSET(addr);
> +	fpci_writel(tegra, page, XUSB_CFG_ARU_C11_CSBRANGE);
> +	return fpci_readl(tegra, XUSB_CFG_CSB_BASE_ADDR + offset);
> +}

I assume some higher level has the required locking or single-threading
so that the keyhole register accesses don't get interleaved?

> +static void tegra_xhci_cfg(struct tegra_xhci_hcd *tegra)
> +{
> +	u32 reg;
> +
> +	reg = ipfs_readl(tegra, IPFS_XUSB_HOST_CONFIGURATION_0);
> +	reg |= IPFS_EN_FPCI;
> +	ipfs_writel(tegra, reg, IPFS_XUSB_HOST_CONFIGURATION_0);
> +	udelay(10);
> +
> +	/* Program Bar0 Space */
> +	reg = fpci_readl(tegra, XUSB_CFG_4);
> +	reg |= tegra->hcd->rsrc_start;

Don't you need to mask out the original value here? I guess whatever is
being written is probably always the same, but it seems scary to assume
that a bootloader, or previous version of a module during development,
didn't write something unexpected there. Perhaps if the HW module's
reset is pulsed we don't need to worry though.

> +static int tegra_xhci_load_firmware(struct tegra_xhci_hcd *tegra)
> +{
> +	struct device *dev = tegra->dev;
> +	struct tegra_xhci_fw_cfgtbl *cfg_tbl;
> +	u64 fw_base;
> +	u32 val;
> +	time_t fw_time;
> +	struct tm fw_tm;
> +
> +	if (csb_readl(tegra, XUSB_CSB_MP_ILOAD_BASE_LO) != 0) {
> +		dev_info(dev, "Firmware already loaded, Falcon state 0x%x\n",
> +			 csb_readl(tegra, XUSB_FALC_CPUCTL));
> +		return 0;
> +	}
> +
> +	cfg_tbl = (struct tegra_xhci_fw_cfgtbl *)tegra->fw_data;

Are there endianness or CPU word size (e.g. ARMv8) issues here; this is
casting the content of a data file to a CPU data structure.

> +static int tegra_xhci_set_ss_clk(struct tegra_xhci_hcd *tegra,
> +				 unsigned long rate)

> +	switch (rate) {
> +	case TEGRA_XHCI_SS_CLK_HIGH_SPEED:
> +		/* Reparent to PLLU_480M. Set div first to avoid overclocking */
> +		old_parent_rate = clk_get_rate(clk_get_parent(clk));
> +		new_parent_rate = clk_get_rate(tegra->pll_u_480m);
> +		div = new_parent_rate / rate;
> +		ret = clk_set_rate(clk, old_parent_rate / div);
> +		if (ret)
> +			return ret;
> +		ret = clk_set_parent(clk, tegra->pll_u_480m);
> +		if (ret)
> +			return ret;

Don't you need to call clk_set_rate() again after reparenting, since the
divisor will be different, and the rounding too.

> +static int tegra_xhci_regulator_enable(struct tegra_xhci_hcd *tegra)
> +{
> +	int ret;
> +
> +	ret = regulator_enable(tegra->s3p3v_reg);
> +	if (ret < 0)
> +		return ret;
> +	ret = regulator_enable(tegra->s1p8v_reg);
> +	if (ret < 0)
> +		goto disable_s3p3v;
> +	ret = regulator_enable(tegra->s1p05v_reg);
> +	if (ret < 0)
> +		goto disable_s1p8v;

Would regulator_bulk_enable() save any code here? Similar in _disable().

> +static const struct tegra_xhci_soc_config tegra124_soc_config = {
> +	.firmware_file = "tegra12x/tegra_xusb_firmware",
> +};

I would prefer an "nvidia/" prefix so everything gets namespaced by vendor.

"tegra12x" isn't the name of the chip, but rather "Tegra124".

"tegra_" and "_firmware" seem redundant, since they're implied by parent
directories.

So, how about "nvidia/tegra124/xusb"? (perhaps with .img or .bin file
extension)

> +static int tegra_xhci_probe(struct platform_device *pdev)

> +	tegra->host_clk = devm_clk_get(&pdev->dev, "xusb_host");
> +	if (IS_ERR(tegra->host_clk)) {
> +		ret = PTR_ERR(tegra->host_clk);
> +		goto put_hcd;
> +	}
> +	tegra->falc_clk = devm_clk_get(&pdev->dev, "xusb_falcon_src");
> +	if (IS_ERR(tegra->falc_clk)) {
> +		ret = PTR_ERR(tegra->falc_clk);
> +		goto put_hcd;
> +	}
...

Seems like devm_clk_get_bulk() would be useful:-)

> +	for (i = 0; i < TEGRA_XHCI_UTMI_PHYS; i++) {
> +		char prop[sizeof("utmi-N")];
> +
> +		sprintf(prop, "utmi-%d", i);

Since this loop is cut/paste 3 times just with the string
"utmi"/"hsic"/"usb3" being different, does it make sense to add an outer
loop over an array of strings instead of duplicating the loo?

> +	ret = request_firmware_nowait(THIS_MODULE, true,
> +				      tegra->soc_config->firmware_file,
> +				      tegra->dev, GFP_KERNEL, tegra,
> +				      tegra_xhci_probe_finish);

I'm not familiar with that API. I assume the point is this works in allh
the following situations:

* Driver is built-in, probes before rootfs is available, firmware
eventually gets loaded a few seconds after rootfs is available.

* Driver is a module and gets loaded from an initrd, firmware is loaded
from initrd essentially immediately.

* Driver is a module and gets loaded from an initrd, firmware eventually
gets loaded a few seconds after rootfs is available.

* Driver is a module and gets loaded from rootfs, firmware is loaded
from rootfs essentially immediately.
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