Re: [PATCH v13 5/5] usb: xhci: provide a debugfs hook for erasing rom

[Mathias Nyman]

On 6.5.2020 9.00, Vinod Koul wrote:
> run "echo 1 > /sys/kernel/debug/renesas-usb/rom_erase" to erase
> firmware when driver is loaded.
> 
> Subsequent init of driver shall reload the firmware
> 
> Signed-off-by: Vinod Koul <vkoul@xxxxxxxxxx>
> ---
>  drivers/usb/host/xhci-pci-renesas.c | 33 +++++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
> 
> diff --git a/drivers/usb/host/xhci-pci-renesas.c b/drivers/usb/host/xhci-pci-renesas.c
> index f7d2445d30ec..fa32ec352dc8 100644
> --- a/drivers/usb/host/xhci-pci-renesas.c
> +++ b/drivers/usb/host/xhci-pci-renesas.c
> @@ -2,6 +2,7 @@
>  /* Copyright (C) 2019-2020 Linaro Limited */
>  
>  #include <linux/acpi.h>
> +#include <linux/debugfs.h>
>  #include <linux/firmware.h>
>  #include <linux/module.h>
>  #include <linux/pci.h>
> @@ -170,6 +171,8 @@ static int renesas_fw_verify(const void *fw_data,
>  	return 0;
>  }
>  
> +static void debugfs_init(struct pci_dev *pdev);
> +
>  static bool renesas_check_rom(struct pci_dev *pdev)
>  {
>  	u16 rom_status;
> @@ -183,6 +186,7 @@ static bool renesas_check_rom(struct pci_dev *pdev)
>  	rom_status &= RENESAS_ROM_STATUS_ROM_EXISTS;
>  	if (rom_status) {
>  		dev_dbg(&pdev->dev, "External ROM exists\n");
> +		debugfs_init(pdev);
>  		return true; /* External ROM exists */
>  	}
>  
> @@ -449,6 +453,34 @@ static void renesas_rom_erase(struct pci_dev *pdev)
>  	dev_dbg(&pdev->dev, "ROM Erase... Done success\n");
>  }
>  
> +static int debugfs_rom_erase(void *data, u64 value)
> +{
> +	struct pci_dev *pdev = data;
> +
> +	if (value == 1) {
> +		dev_dbg(&pdev->dev, "Userspace requested ROM erase\n");
> +		renesas_rom_erase(pdev);
> +		return 0;
> +	}
> +	return -EINVAL;
> +}
> +DEFINE_DEBUGFS_ATTRIBUTE(rom_erase_ops, NULL, debugfs_rom_erase, "%llu\n");
> +
> +static struct dentry *debugfs_root;
> +
> +static void debugfs_init(struct pci_dev *pdev)
> +{
> +	debugfs_root = debugfs_create_dir("renesas_usb", NULL);

This will create a renesas_usb directory right under debugfs root.
xhci has its own struct dentry xhci_debugfs_root; 
Use that as parent instead
 
Also note that debugs_create_dir() can fail, for example if debugfs isn't supported.    

- Mathias