Re: [PATCH 3/3] firmware: zynqmp-fpga: do not use DMA coherent memory for bitstream

[Lucas Stach <l.stach@pengutronix.de>]

Am Mittwoch, dem 18.08.2021 um 15:35 +0200 schrieb Michael Tretter:
> Trying to do unaligned access of coherent memory on AArch64 will lead to
> an abort. This can happen when the FPGA loader copies the bitstream to
> the temporary buffer for the transfer to the FPGA.
> 
> Convert the driver to use regular memory for the temporary buffer to
> prevent the issue.
> 
> Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
> ---
>  drivers/firmware/zynqmp-fpga.c | 20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/firmware/zynqmp-fpga.c b/drivers/firmware/zynqmp-fpga.c
> index 667910479aa7..0a0e7e880849 100644
> --- a/drivers/firmware/zynqmp-fpga.c
> +++ b/drivers/firmware/zynqmp-fpga.c
> @@ -203,7 +203,7 @@ static int fpgamgr_program_finish(struct firmware_handler *fh)
>  	size_t body_length;
>  	int header_length = 0;
>  	enum xilinx_byte_order byte_order;
> -	u64 addr;
> +	dma_addr_t addr;
>  	int status = 0;
>  	u8 flags = ZYNQMP_FPGA_BIT_ONLY_BIN;
>  
> @@ -240,13 +240,19 @@ static int fpgamgr_program_finish(struct firmware_handler *fh)
>  	 * memory. Allocate some extra space at the end of the buffer for the
>  	 * bitstream size.
>  	 */
> -	buf_aligned = dma_alloc_coherent(body_length + sizeof(buf_size),
> -					 DMA_ADDRESS_BROKEN);
> +	buf_aligned = dma_alloc(body_length + sizeof(u32));
>  	if (!buf_aligned) {
>  		status = -ENOBUFS;
>  		goto err_free;
>  	}
>  
> +	addr = dma_map_single(&mgr->dev, buf_aligned,
> +			      body_length + sizeof(u32), DMA_TO_DEVICE);
> +	if (dma_mapping_error(&mgr->dev, addr)) {
> +		status = -EFAULT;
> +		goto err_free;
> +	}
> +
Usage of both dma_map_single and explicit dma_sync_single_for_* for a
single transfer looks odd. dma_map_single already does the cache sync,
which you then do a second time in the sync calls.

Instead you should move this dma_map_single call to the place where you
added the dma_sync_single_for_device and replace the
dma_sync_single_for_cpu with a dma_unmap_single.

Regards,
Lucas

>  	if (!(mgr->features & ZYNQMP_PM_FEATURE_BYTE_ORDER_IRREL) &&
>  	    byte_order == XILINX_BYTE_ORDER_BIN)
>  		copy_words_swapped((u32 *)buf_aligned, body,
> @@ -254,8 +260,6 @@ static int fpgamgr_program_finish(struct firmware_handler *fh)
>  	else
>  		memcpy((u32 *)buf_aligned, body, body_length);
>  
> -	addr = (u64)buf_aligned;
> -
>  	if (mgr->features & ZYNQMP_PM_FEATURE_SIZE_NOT_NEEDED) {
>  		buf_size = body_length;
>  	} else {
> @@ -263,11 +267,13 @@ static int fpgamgr_program_finish(struct firmware_handler *fh)
>  		buf_size = addr + body_length;
>  	}
>  
> -	status = mgr->eemi_ops->fpga_load(addr, buf_size, flags);
> +	dma_sync_single_for_device(addr, body_length + sizeof(u32), DMA_TO_DEVICE);
> +	status = mgr->eemi_ops->fpga_load((u64)addr, buf_size, flags);
> +	dma_sync_single_for_cpu(addr, body_length + sizeof(u32), DMA_TO_DEVICE);
>  	if (status < 0)
>  		dev_err(&mgr->dev, "unable to load fpga\n");
>  
> -	dma_free_coherent(buf_aligned, 0, body_length + sizeof(buf_size));
> +	dma_free(buf_aligned);
>  
>   err_free:
>  	free(mgr->buf);



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