Re: [PATCH v3] xhci: Bad Ethernet performance plugged in ASM1042A host

[Ian Pilcher <arequipeno@xxxxxxxxx>]

On 06/15/2017 01:58 AM, Jiahau Chang wrote:
> +void usb_asmedia_modifyflowcontrol(struct pci_dev *pdev)
> +{
> +	unsigned char value;
> +	unsigned long wait_time_count;
> +
> +	/*check device can accept command*/
> +	wait_time_count = 1000;
> +	while (wait_time_count) {
> +		pci_read_config_byte(pdev, ASMT_CONTROL_REG, &value);
> +		if (value == 0xff) {
> +			dev_dbg(&pdev->dev, "%s: check_ready ERROR", __func__);
> +			goto err_exit;
> +		}
> +		if ((value & ASMT_CONTROL_WRITE_BIT) == 0)
> +			break;
> +		wait_time_count--;
> +		usleep(50);
> +	}
> +	if (wait_time_count == 0) {
> +		dev_dbg(&pdev->dev, "%s: check_write_ready timeout", __func__);
> +		goto err_exit;
> +	}
> +	/* send command and address to device */
> +	pci_write_config_dword(pdev, ASMT_DATA_WRITE0_REG, ASMT_WRITEREG_CMD);
> +	pci_write_config_dword(pdev, ASMT_DATA_WRITE1_REG, ASMT_FLOWCTL_ADDR);
> +	pci_write_config_byte(pdev, ASMT_CONTROL_REG, ASMT_CONTROL_WRITE_BIT);
> +	wait_time_count = 1000;
> +	/* wait device receive the data */
> +	while (wait_time_count) {
> +		pci_read_config_byte(pdev, ASMT_CONTROL_REG, &value);
> +		if (value == 0xff) {
> +			dev_dbg(&pdev->dev, "%s: wait_ready ERROR", __func__);
> +			goto err_exit;
> +		}
> +		if ((value & ASMT_CONTROL_WRITE_BIT) == 0)
> +			break;
> +		wait_time_count--;
> +		usleep(50);
> +	}
> +	if (wait_time_count == 0) {
> +		dev_dbg(&pdev->dev, "%s: wait_write_ready timeout", __func__);
> +		goto err_exit;
> +	}
> +	/* send data to device */
> +	pci_write_config_dword(pdev, ASMT_DATA_WRITE0_REG, ASMT_FLOWCTL_DATA);
> +	pci_write_config_dword(pdev, ASMT_DATA_WRITE1_REG, ASMT_PSEUDO_DATA);
> +	pci_write_config_byte(pdev, ASMT_CONTROL_REG, ASMT_CONTROL_WRITE_BIT);
> +err_exit:
> +	return;
> +}

As others have pointed out, this flow is not very clear to the first-
time reader.  Maybe something like this (WARNING untested):

static int usb_asmedia_wait_write(struct pci_dev *pdev, unsigned long 
wait_usec)
{
	unsigned long wait_count;
	unsigned char value;

	for (wait_count = wait_usec / 50; wait_count > 0; --wait_count) {

		pci_read_config_byte(pdev, ASMT_CONTROL_REG, &value);

		if (value == 0xff) {
			dev_dbg(&pdev->dev, "%s: check_ready ERROR", __func__);
			return -1;
		}

		if ((value & ASMT_CONTROL_WRITE_BIT) == 0)
			return 0;
	}

	dev_dbg(&pdev->dev, "%s: check_write_ready timeout", __func__);
	return -1;
}

void usb_asmedia_modifyflowcontrol(struct pci_dev *dev)
{
	if (usb_asmedia_wait_write(pdev, 50000) != 0)
		goto err_exit;

	/* send command and address to device */
	pci_write_config_dword(pdev, ASMT_DATA_WRITE0_REG, ASMT_WRITEREG_CMD);
	pci_write_config_dword(pdev, ASMT_DATA_WRITE1_REG, ASMT_FLOWCTL_ADDR);
	pci_write_config_byte(pdev, ASMT_CONTROL_REG, ASMT_CONTROL_WRITE_BIT);

	if (usb_asmedia_wait_write(pdev, 50000) != 0)
		goto err_exit;

	/* send data to device */
	pci_write_config_dword(pdev, ASMT_DATA_WRITE0_REG, ASMT_FLOWCTL_DATA);
	pci_write_config_dword(pdev, ASMT_DATA_WRITE1_REG, ASMT_PSEUDO_DATA);
	pci_write_config_byte(pdev, ASMT_CONTROL_REG, ASMT_CONTROL_WRITE_BIT);

err_exit:
	return;
}


--
========================================================================
Ian Pilcher                                         arequipeno@xxxxxxxxx
-------- "I grew up before Mark Zuckerberg invented friendship" --------
========================================================================

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