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From:   Peter Chen <peter.chen@nxp.com>
To:     Jayshri Pawar <jpawar@cadence.com>
CC:     "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "felipe.balbi@linux.intel.com" <felipe.balbi@linux.intel.com>,
        "heikki.krogerus@linux.intel.com" <heikki.krogerus@linux.intel.com>,
        "rogerq@ti.com" <rogerq@ti.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "jbergsagel@ti.com" <jbergsagel@ti.com>,
        "nsekhar@ti.com" <nsekhar@ti.com>, "nm@ti.com" <nm@ti.com>,
        "kurahul@cadence.com" <kurahul@cadence.com>,
        "pawell@cadence.com" <pawell@cadence.com>,
        "sparmar@cadence.com" <sparmar@cadence.com>
Subject: Re: [RFC PATCH] usb: gadget: f_tcm: Added DMA32 flag while allocation
 of command buffer
Thread-Topic: [RFC PATCH] usb: gadget: f_tcm: Added DMA32 flag while
 allocation of command buffer
Thread-Index: AQHVmgy0AO3oXPQWj0iIFuuXV9ypwqeJ+SiA
Date:   Thu, 14 Nov 2019 02:50:42 +0000
Message-ID: <20191114025301.GD30608@b29397-desktop>
References: <1573640672-10344-1-git-send-email-jpawar@cadence.com>
In-Reply-To: <1573640672-10344-1-git-send-email-jpawar@cadence.com>
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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.=20
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=20
use case.

Peter

>=20
> 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(-)
>=20
> diff --git a/drivers/usb/gadget/function/f_tcm.c b/drivers/usb/gadget/fun=
ction/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 *cm=
d)
>  	}
> =20
>  	if (!gadget->sg_supported) {
> -		cmd->data_buf =3D kmalloc(se_cmd->data_length, GFP_ATOMIC);
> +		cmd->data_buf =3D kmalloc(se_cmd->data_length, GFP_ATOMIC |
> +					gadget->dma_flag);
>  		if (!cmd->data_buf)
>  			return -ENOMEM;
> =20
> @@ -257,7 +258,8 @@ static int bot_send_write_request(struct usbg_cmd *cm=
d)
>  	}
> =20
>  	if (!gadget->sg_supported) {
> -		cmd->data_buf =3D kmalloc(se_cmd->data_length, GFP_KERNEL);
> +		cmd->data_buf =3D kmalloc(se_cmd->data_length, GFP_KERNEL |
> +					gadget->dma_flag);
>  		if (!cmd->data_buf)
>  			return -ENOMEM;
> =20
> @@ -305,6 +307,7 @@ static void bot_cmd_complete(struct usb_ep *ep, struc=
t usb_request *req)
>  static int bot_prepare_reqs(struct f_uas *fu)
>  {
>  	int ret;
> +	struct usb_gadget *gadget =3D fuas_to_gadget(fu);
> =20
>  	fu->bot_req_in =3D 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 =3D bot_status_complete;
>  	fu->bot_status.csw.Signature =3D cpu_to_le32(US_BULK_CS_SIGN);
> =20
> -	fu->cmd.buf =3D kmalloc(fu->ep_out->maxpacket, GFP_KERNEL);
> +	fu->cmd.buf =3D kmalloc(fu->ep_out->maxpacket, GFP_KERNEL |
> +				gadget->dma_flag);
>  	if (!fu->cmd.buf)
>  		goto err_buf;
> =20
> @@ -515,7 +519,8 @@ static int uasp_prepare_r_request(struct usbg_cmd *cm=
d)
>  	struct uas_stream *stream =3D cmd->stream;
> =20
>  	if (!gadget->sg_supported) {
> -		cmd->data_buf =3D kmalloc(se_cmd->data_length, GFP_ATOMIC);
> +		cmd->data_buf =3D kmalloc(se_cmd->data_length, GFP_ATOMIC |
> +					gadget->dma_flag);
>  		if (!cmd->data_buf)
>  			return -ENOMEM;
> =20
> @@ -763,11 +768,13 @@ static int uasp_alloc_stream_res(struct f_uas *fu, =
struct uas_stream *stream)
> =20
>  static int uasp_alloc_cmd(struct f_uas *fu)
>  {
> +	struct usb_gadget *gadget =3D fuas_to_gadget(fu);
>  	fu->cmd.req =3D usb_ep_alloc_request(fu->ep_cmd, GFP_KERNEL);
>  	if (!fu->cmd.req)
>  		goto err;
> =20
> -	fu->cmd.buf =3D kmalloc(fu->ep_cmd->maxpacket, GFP_KERNEL);
> +	fu->cmd.buf =3D kmalloc(fu->ep_cmd->maxpacket, GFP_KERNEL |
> +				gadget->dma_flag);
>  	if (!fu->cmd.buf)
>  		goto err_buf;
> =20
> @@ -980,7 +987,8 @@ static int usbg_prepare_w_request(struct usbg_cmd *cm=
d, struct usb_request *req)
>  	struct usb_gadget *gadget =3D fuas_to_gadget(fu);
> =20
>  	if (!gadget->sg_supported) {
> -		cmd->data_buf =3D kmalloc(se_cmd->data_length, GFP_ATOMIC);
> +		cmd->data_buf =3D kmalloc(se_cmd->data_length, GFP_ATOMIC |
> +					gadget->dma_flag);
>  		if (!cmd->data_buf)
>  			return -ENOMEM;
> =20
> 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))
> =20
> --=20
> 2.20.1
>=20

--=20

Thanks,
Peter Chen=