Re: [PATCH v4 3/4] mt76: speed up usb bulk copy

[Lorenzo Bianconi <lorenzo.bianconi@redhat.com>]

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> Use larger batches for usb copy to speed this operation up. Otherwise it
> would be too slow for copying new beacons or broadcast frames over usb.
> Assure, that always a multiple of 4 Bytes is copied, as outlined in
> 850e8f6fbd "mt76: round up length on mt76_wr_copy" from Felix Fietkau.
> 
> Signed-off-by: Markus Theil <markus.theil@tu-ilmenau.de>
> ---
>  drivers/net/wireless/mediatek/mt76/mt76.h |  2 +-
>  drivers/net/wireless/mediatek/mt76/usb.c  | 24 +++++++++++++++++------
>  2 files changed, 19 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt76.h b/drivers/net/wireless/mediatek/mt76/mt76.h
> index 8aec7ccf2d79..7a6f5d097a3d 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt76.h
> +++ b/drivers/net/wireless/mediatek/mt76/mt76.h
> @@ -383,7 +383,7 @@ enum mt76u_out_ep {
>  struct mt76_usb {
>  	struct mutex usb_ctrl_mtx;
>  	union {
> -		u8 data[32];
> +		u8 data[128];
>  		__le32 reg_val;
>  	};
>  
> diff --git a/drivers/net/wireless/mediatek/mt76/usb.c b/drivers/net/wireless/mediatek/mt76/usb.c
> index 20c6fe510e9d..f1f67b0f8265 100644
> --- a/drivers/net/wireless/mediatek/mt76/usb.c
> +++ b/drivers/net/wireless/mediatek/mt76/usb.c
> @@ -149,18 +149,30 @@ static void mt76u_copy(struct mt76_dev *dev, u32 offset,
>  		       const void *data, int len)
>  {
>  	struct mt76_usb *usb = &dev->usb;
> -	const u32 *val = data;
> -	int i, ret;
> +	const u8 *val = data;
> +	int ret;
> +	int current_batch_size;
> +	int i = 0;
> +
> +	/* Assure that always a multiple of 4 bytes are copied,
> +	 * otherwise beacons can be corrupted.
> +	 * See: "mt76: round up length on mt76_wr_copy"
> +	 * Commit 850e8f6fbd5d0003b0
> +	 */
> +	len = DIV_ROUND_UP(len, 4) * 4;
>  
>  	mutex_lock(&usb->usb_ctrl_mtx);
> -	for (i = 0; i < DIV_ROUND_UP(len, 4); i++) {
> -		put_unaligned(val[i], (u32 *)usb->data);
> +	while (i < len) {
> +		current_batch_size = min((int)sizeof(usb->data), len - i);

What about using min_t() here?

> +		memcpy(usb->data, val + i, current_batch_size);
>  		ret = __mt76u_vendor_request(dev, MT_VEND_MULTI_WRITE,
>  					     USB_DIR_OUT | USB_TYPE_VENDOR,
> -					     0, offset + i * 4, usb->data,
> -					     sizeof(u32));
> +					     0, offset + i, usb->data,
> +					     current_batch_size);
>  		if (ret < 0)
>  			break;
> +
> +		i += current_batch_size;
>  	}
>  	mutex_unlock(&usb->usb_ctrl_mtx);
>  }
> -- 
> 2.24.0
> 

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