Subject: Re: [RFC PATCH v2 2/3] usb: xhci-mtk: modify the SOF/ITP interval for mt8195

From: Mathias Nyman <[email-masked]>
Date: Mon, 8 Feb 2021 13:43:13 +0200

On 7.2.2021 4.27, Chunfeng Yun wrote:
> Hi Mathias,
> 
> On Wed, 2021-02-03 at 18:26 +0800, Chunfeng Yun wrote:
>> There are 4 USB controllers on MT8195, the controllers (IP1~IP3,
>> exclude IP0) have a wrong default SOF/ITP interval which is
>> calculated from the frame counter clock 24Mhz by default, but
>> in fact, the frame counter clock is 48Mhz, so we should set
>> the accurate interval according to 48Mhz for those controllers.
>> Note: the first controller no need set it.
>>
>> Signed-off-by: Chunfeng Yun <[email-masked]>
>> ---
>> v2: fix typo of comaptible
>> ---
>>  drivers/usb/host/xhci-mtk.c | 63 +++++++++++++++++++++++++++++++++++++
>>  1 file changed, 63 insertions(+)
>>
>> diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c
>> index 8f321f39ab96..0a68c4ac8b48 100644
>> --- a/drivers/usb/host/xhci-mtk.c
>> +++ b/drivers/usb/host/xhci-mtk.c
>> @@ -68,11 +68,71 @@
>>  #define SSC_IP_SLEEP_EN	BIT(4)
>>  #define SSC_SPM_INT_EN		BIT(1)
>>  
> Can I Read/Write the following xHCI controller's registers  in
> xhci-mtk.c?
> 
> Ideally, xhci-mtk.c should not access them, because xhci-mtk is only a
> glue driver used to initialize clocks/power and IPPC registers which
> don't belong to xHCI controller.
> 

These *_EOF registers look like they are Mediatek vendor specific registers
and not part of public xHCI register-level spec. 
So I think accessing them from xhci-mtk.c makes sense.

If those register offsets are hardcoded like this in the Mediatek spec then
this is fine, but if those offsets are found from a vendor specific xHCI
extended capability entry (see xhci spec section 7) then we should dig them out
from there. 
>> +/* xHCI csr */
>> +#define LS_EOF			0x930
>> +#define LS_EOF_OFFSET		0x89
>> +
>> +#define FS_EOF			0x934
>> +#define FS_EOF_OFFSET		0x2e
>> +
>> +#define SS_GEN1_EOF		0x93c
>> +#define SS_GEN1_EOF_OFFSET	0x78
>> +
>> +#define HFCNTR_CFG		0x944
>> +#define ITP_DELTA_CLK		(0xa << 1)
>> +#define ITP_DELTA_CLK_MASK	GENMASK(5, 1)
>> +#define FRMCNT_LEV1_RANG	(0x12b << 8)
>> +#define FRMCNT_LEV1_RANG_MASK	GENMASK(19, 8)
>> +
>> +#define SS_GEN2_EOF		0x990
>> +#define SS_GEN2_EOF_OFFSET	0x3c
>> +#define EOF_OFFSET_MASK		GENMASK(11, 0)
>> +
>>  enum ssusb_uwk_vers {
>>  	SSUSB_UWK_V1 = 1,
>>  	SSUSB_UWK_V2,
>>  };
>>  
>> +/*
>> + * MT8195 has 4 controllers, the controller1~3's default SOF/ITP interval
>> + * is calculated from the frame counter clock 24M, but in fact, the clock
>> + * is 48M, so need change the interval.
>> + */
>> +static void xhci_mtk_set_frame_interval(struct xhci_hcd_mtk *mtk)
>> +{
>> +	struct device *dev = mtk->dev;
>> +	struct usb_hcd *hcd = mtk->hcd;
>> +	u32 value;
>> +
>> +	if (!of_device_is_compatible(dev->of_node, "mediatek,mt8195-xhci"))
>> +		return;
>> +
>> +	value = readl(hcd->regs + HFCNTR_CFG);
>> +	value &= ~(ITP_DELTA_CLK_MASK | FRMCNT_LEV1_RANG_MASK);
>> +	value |= (ITP_DELTA_CLK | FRMCNT_LEV1_RANG);
>> +	writel(value, hcd->regs + HFCNTR_CFG);
>> +
>> +	value = readl(hcd->regs + LS_EOF);
>> +	value &= ~EOF_OFFSET_MASK;
>> +	value |= LS_EOF_OFFSET;
>> +	writel(value, hcd->regs + LS_EOF);
>> +
>> +	value = readl(hcd->regs + FS_EOF);
>> +	value &= ~EOF_OFFSET_MASK;
>> +	value |= FS_EOF_OFFSET;
>> +	writel(value, hcd->regs + FS_EOF);
>> +
>> +	value = readl(hcd->regs + SS_GEN1_EOF);
>> +	value &= ~EOF_OFFSET_MASK;
>> +	value |= SS_GEN1_EOF_OFFSET;
>> +	writel(value, hcd->regs + SS_GEN1_EOF);
>> +
>> +	value = readl(hcd->regs + SS_GEN2_EOF);
>> +	value &= ~EOF_OFFSET_MASK;
>> +	value |= SS_GEN2_EOF_OFFSET;
>> +	writel(value, hcd->regs + SS_GEN2_EOF);

Minor nit about names,
Register offsets from MMIO start are named *_EOF while clock multipliers? are named *_EOF_OFFSET.
This was a bit confusing

Thanks
-Mathias

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