Re: [PATCH v10 1/2] usb: dwc3: qcom: Add interconnect support in dwc3 driver

[Matthias Kaehlcke <mka@chromium.org>]

Hi Sandeep,

On Thu, Jul 23, 2020 at 11:57:36PM +0530, Sandeep Maheswaram wrote:
> Add interconnect support in dwc3-qcom driver to vote for bus
> bandwidth.
> 
> This requires for two different paths - from USB to
> DDR. The other is from APPS to USB.
> 
> Signed-off-by: Sandeep Maheswaram <sanm@codeaurora.org>
> Signed-off-by: Chandana Kishori Chiluveru <cchiluve@codeaurora.org>
> ---
>  drivers/usb/dwc3/dwc3-qcom.c | 127 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 125 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
> index e1e78e9..712efb7 100644
> --- a/drivers/usb/dwc3/dwc3-qcom.c
> +++ b/drivers/usb/dwc3/dwc3-qcom.c
> @@ -13,6 +13,7 @@
>  #include <linux/module.h>
>  #include <linux/kernel.h>
>  #include <linux/extcon.h>
> +#include <linux/interconnect.h>
>  #include <linux/of_platform.h>
>  #include <linux/platform_device.h>
>  #include <linux/phy/phy.h>
> @@ -43,6 +44,14 @@
>  #define SDM845_QSCRATCH_SIZE			0x400
>  #define SDM845_DWC3_CORE_SIZE			0xcd00
>  
> +/* Interconnect path bandwidths in MBps */
> +#define USB_MEMORY_AVG_HS_BW MBps_to_icc(240)
> +#define USB_MEMORY_PEAK_HS_BW MBps_to_icc(700)
> +#define USB_MEMORY_AVG_SS_BW  MBps_to_icc(1000)
> +#define USB_MEMORY_PEAK_SS_BW MBps_to_icc(2500)
> +#define APPS_USB_AVG_BW 0
> +#define APPS_USB_PEAK_BW MBps_to_icc(40)
> +
>  struct dwc3_acpi_pdata {
>  	u32			qscratch_base_offset;
>  	u32			qscratch_base_size;
> @@ -76,6 +85,8 @@ struct dwc3_qcom {
>  	enum usb_dr_mode	mode;
>  	bool			is_suspended;
>  	bool			pm_suspended;
> +	struct icc_path		*icc_path_ddr;
> +	struct icc_path		*icc_path_apps;
>  };
>  
>  static inline void dwc3_qcom_setbits(void __iomem *base, u32 offset, u32 val)
> @@ -190,6 +201,103 @@ static int dwc3_qcom_register_extcon(struct dwc3_qcom *qcom)
>  	return 0;
>  }
>  
> +static int dwc3_qcom_interconnect_enable(struct dwc3_qcom *qcom)
> +{
> +	int ret;
> +
> +	ret = icc_enable(qcom->icc_path_ddr);
> +	if (ret)
> +		return ret;
> +
> +	ret = icc_enable(qcom->icc_path_apps);
> +	if (ret)
> +		return icc_disable(qcom->icc_path_ddr);

You are returning the result of icc_disable(), but it should be the
previous error. Just do

		icc_disable(qcom->icc_path_ddr);

and use the below statement for returning (if not it should be 'return 0').

> +
> +	return ret;
> +}
> +
> +static int dwc3_qcom_interconnect_disable(struct dwc3_qcom *qcom)
> +{
> +	int ret;
> +
> +	ret = icc_disable(qcom->icc_path_ddr);
> +	if (ret)
> +		return ret;
> +
> +	ret = icc_disable(qcom->icc_path_apps);
> +	if (ret)
> +		goto err_reenable_memory_path;

Please make the error handling in _enable() and _disable() symmetrical, either
call icc_enable/disable() directly or use a goto in both functions (IMO the goto
is not needed in this case, it makes the code more complex rather than
simplifying it).

> +
> +	return 0;
> +
> +	/* Re-enable things in the event of an error */
> +err_reenable_memory_path:
> +	dwc3_qcom_interconnect_enable(qcom);

Why this function which disables both paths and not just
icc_enable(qcom->icc_path_ddr), analogous to dwc3_qcom_interconnect_enable()?

> +
> +	return ret;
> +}
> +
> +/**
> + * dwc3_qcom_interconnect_init() - Get interconnect path handles
> + * and set bandwidhth.
> + * @qcom:			Pointer to the concerned usb core.
> + *
> + */
> +static int dwc3_qcom_interconnect_init(struct dwc3_qcom *qcom)
> +{
> +	struct device *dev = qcom->dev;
> +	int ret;
> +
> +	qcom->icc_path_ddr = of_icc_get(dev, "usb-ddr");
> +	if (IS_ERR(qcom->icc_path_ddr)) {
> +		dev_err(dev, "failed to get usb-ddr path: %ld\n",
> +			PTR_ERR(qcom->icc_path_ddr));
> +		return PTR_ERR(qcom->icc_path_ddr);
> +	}
> +
> +	qcom->icc_path_apps = of_icc_get(dev, "apps-usb");
> +	if (IS_ERR(qcom->icc_path_apps)) {
> +		dev_err(dev, "failed to get apps-usb path: %ld\n",
> +				PTR_ERR(qcom->icc_path_apps));
> +		return PTR_ERR(qcom->icc_path_apps);
> +	}
> +
> +	if (usb_get_maximum_speed(&qcom->dwc3->dev) >= USB_SPEED_SUPER ||
> +			usb_get_maximum_speed(&qcom->dwc3->dev) == USB_SPEED_UNKNOWN)
> +		ret = icc_set_bw(qcom->icc_path_ddr,
> +			USB_MEMORY_AVG_SS_BW, USB_MEMORY_PEAK_SS_BW);
> +	else
> +		ret = icc_set_bw(qcom->icc_path_ddr,
> +			USB_MEMORY_AVG_HS_BW, USB_MEMORY_PEAK_HS_BW);
> +
> +	if (ret) {
> +		dev_err(dev, "failed to set bandwidth for usb-ddr path: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = icc_set_bw(qcom->icc_path_apps,
> +		APPS_USB_AVG_BW, APPS_USB_PEAK_BW);
> +

nit: remove empty line, the call and the if block belong together.

> +	if (ret) {
> +		dev_err(dev, "failed to set bandwidth for apps-usb path: %d\n", ret);
> +		return ret;
> +	}