Re: [RFC PATCH] usb: gadget: f_tcm: Added DMA32 flag while allocation of command buffer

[Peter Chen <peter.chen@nxp.com>]

On 19-11-13 10:24:32, Jayshri Pawar wrote:
> There is a problem when function driver allocate memory for buffer
> used by DMA from outside dma_mask space.
> It appears during testing f_tcm driver with cdns3 controller.
> In the result cdns3 driver was not able to map virtual buffer to DMA.
> This fix should be improved depending on dma_mask associated with device.
> Adding GFP_DMA32 flag while allocationg command data buffer only for 32
> bit controllers.

Hi Jayshri,

This issue should be fixed by setting DMA_MASK correctly for controller,
you can't limit user's memory region. At usb_ep_queue, the UDC driver
will call DMA MAP API, for Cadence, it is usb_gadget_map_request_by_dev. 
For the system without SMMU (IO-MMU), it will use swiotlb to make sure
the data buffer used for DMA transfer is within DMA mask for controller,
There is a reserved low memory region for debounce buffer in swiotlb 
use case.

Peter

> 
> Signed-off-by: Pawel Laszczak <pawell@cadence.com>
> Signed-off-by: Jayshri Pawar <jpawar@cadence.com>
> ---
>  drivers/usb/gadget/function/f_tcm.c | 20 ++++++++++++++------
>  include/linux/usb/gadget.h          |  2 ++
>  2 files changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/usb/gadget/function/f_tcm.c b/drivers/usb/gadget/function/f_tcm.c
> index 36504931b2d1..a78d5fad3d84 100644
> --- a/drivers/usb/gadget/function/f_tcm.c
> +++ b/drivers/usb/gadget/function/f_tcm.c
> @@ -213,7 +213,8 @@ static int bot_send_read_response(struct usbg_cmd *cmd)
>  	}
>  
>  	if (!gadget->sg_supported) {
> -		cmd->data_buf = kmalloc(se_cmd->data_length, GFP_ATOMIC);
> +		cmd->data_buf = kmalloc(se_cmd->data_length, GFP_ATOMIC |
> +					gadget->dma_flag);
>  		if (!cmd->data_buf)
>  			return -ENOMEM;
>  
> @@ -257,7 +258,8 @@ static int bot_send_write_request(struct usbg_cmd *cmd)
>  	}
>  
>  	if (!gadget->sg_supported) {
> -		cmd->data_buf = kmalloc(se_cmd->data_length, GFP_KERNEL);
> +		cmd->data_buf = kmalloc(se_cmd->data_length, GFP_KERNEL |
> +					gadget->dma_flag);
>  		if (!cmd->data_buf)
>  			return -ENOMEM;
>  
> @@ -305,6 +307,7 @@ static void bot_cmd_complete(struct usb_ep *ep, struct usb_request *req)
>  static int bot_prepare_reqs(struct f_uas *fu)
>  {
>  	int ret;
> +	struct usb_gadget *gadget = fuas_to_gadget(fu);
>  
>  	fu->bot_req_in = usb_ep_alloc_request(fu->ep_in, GFP_KERNEL);
>  	if (!fu->bot_req_in)
> @@ -327,7 +330,8 @@ static int bot_prepare_reqs(struct f_uas *fu)
>  	fu->bot_status.req->complete = bot_status_complete;
>  	fu->bot_status.csw.Signature = cpu_to_le32(US_BULK_CS_SIGN);
>  
> -	fu->cmd.buf = kmalloc(fu->ep_out->maxpacket, GFP_KERNEL);
> +	fu->cmd.buf = kmalloc(fu->ep_out->maxpacket, GFP_KERNEL |
> +				gadget->dma_flag);
>  	if (!fu->cmd.buf)
>  		goto err_buf;
>  
> @@ -515,7 +519,8 @@ static int uasp_prepare_r_request(struct usbg_cmd *cmd)
>  	struct uas_stream *stream = cmd->stream;
>  
>  	if (!gadget->sg_supported) {
> -		cmd->data_buf = kmalloc(se_cmd->data_length, GFP_ATOMIC);
> +		cmd->data_buf = kmalloc(se_cmd->data_length, GFP_ATOMIC |
> +					gadget->dma_flag);
>  		if (!cmd->data_buf)
>  			return -ENOMEM;
>  
> @@ -763,11 +768,13 @@ static int uasp_alloc_stream_res(struct f_uas *fu, struct uas_stream *stream)
>  
>  static int uasp_alloc_cmd(struct f_uas *fu)
>  {
> +	struct usb_gadget *gadget = fuas_to_gadget(fu);
>  	fu->cmd.req = usb_ep_alloc_request(fu->ep_cmd, GFP_KERNEL);
>  	if (!fu->cmd.req)
>  		goto err;
>  
> -	fu->cmd.buf = kmalloc(fu->ep_cmd->maxpacket, GFP_KERNEL);
> +	fu->cmd.buf = kmalloc(fu->ep_cmd->maxpacket, GFP_KERNEL |
> +				gadget->dma_flag);
>  	if (!fu->cmd.buf)
>  		goto err_buf;
>  
> @@ -980,7 +987,8 @@ static int usbg_prepare_w_request(struct usbg_cmd *cmd, struct usb_request *req)
>  	struct usb_gadget *gadget = fuas_to_gadget(fu);
>  
>  	if (!gadget->sg_supported) {
> -		cmd->data_buf = kmalloc(se_cmd->data_length, GFP_ATOMIC);
> +		cmd->data_buf = kmalloc(se_cmd->data_length, GFP_ATOMIC |
> +					gadget->dma_flag);
>  		if (!cmd->data_buf)
>  			return -ENOMEM;
>  
> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
> index 124462d65eac..d6c9cd222600 100644
> --- a/include/linux/usb/gadget.h
> +++ b/include/linux/usb/gadget.h
> @@ -373,6 +373,7 @@ struct usb_gadget_ops {
>   * @connected: True if gadget is connected.
>   * @lpm_capable: If the gadget max_speed is FULL or HIGH, this flag
>   *	indicates that it supports LPM as per the LPM ECN & errata.
> + * @dma_flag: dma zone to be used for buffer allocation.
>   *
>   * Gadgets have a mostly-portable "gadget driver" implementing device
>   * functions, handling all usb configurations and interfaces.  Gadget
> @@ -427,6 +428,7 @@ struct usb_gadget {
>  	unsigned			deactivated:1;
>  	unsigned			connected:1;
>  	unsigned			lpm_capable:1;
> +	unsigned int			dma_flag;
>  };
>  #define work_to_gadget(w)	(container_of((w), struct usb_gadget, work))
>  
> -- 
> 2.20.1
> 

-- 

Thanks,
Peter Chen