linux-kernel - Re: [PATCH] parisc: DMA API: return error instead of BUG

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Date:   Wed, 5 Jul 2017 21:36:09 +0200
From:   Helge Deller <deller@....de>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        jejb@...isc-linux.org, linux-parisc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] parisc: DMA API: return error instead of BUG_ON for dma
 ops on non dma devs

Hi Christoph,

On 05.07.2017 20:57, Christoph Hellwig wrote:
> I've got a tree pending that removes DMA_ERROR_CODE, and it's been
> in linux-next for a while.

I had the parisc patch in for-next as well and didn't received
any warnings.
 
> While this won't compile-time conflict with this patch and will
> basically revert the effect.
> 
> Can you please test the patch below and send it to Linus ASAP so that
> I can send the pull request for the dma-mapping tree?

I'll do that now.


> ---
> From 85942d54e2f0ad5f4b4e074ce2e271be17b31274 Mon Sep 17 00:00:00 2001
> From: Christoph Hellwig <hch@....de>
> Date: Tue, 4 Jul 2017 19:55:06 -0700
> Subject: parisc: ->mapping_error
> 
> DMA_ERROR_CODE already went away in linux-next, but parisc unfortunately
> added a new instance of it without any review as far as I can tell.

Can we please change this to something like 
"Prepare parisc to get rid of DMA_ERROR_CODE tree-wide" ?
It's somewhat more neutral.

Helge

> 
> Move the two iommu drivers to report errors through ->mapping_error.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  arch/parisc/include/asm/dma-mapping.h |  2 --
>  drivers/parisc/ccio-dma.c             | 10 +++++++++-
>  drivers/parisc/sba_iommu.c            | 10 +++++++++-
>  3 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/parisc/include/asm/dma-mapping.h b/arch/parisc/include/asm/dma-mapping.h
> index 9a2a8956a695..2b16282add69 100644
> --- a/arch/parisc/include/asm/dma-mapping.h
> +++ b/arch/parisc/include/asm/dma-mapping.h
> @@ -20,8 +20,6 @@
>  ** flush/purge and allocate "regular" cacheable pages for everything.
>  */
>  
> -#define DMA_ERROR_CODE	(~(dma_addr_t)0)
> -
>  #ifdef CONFIG_PA11
>  extern const struct dma_map_ops pcxl_dma_ops;
>  extern const struct dma_map_ops pcx_dma_ops;
> diff --git a/drivers/parisc/ccio-dma.c b/drivers/parisc/ccio-dma.c
> index 56c93f096de9..6aa1e7f6672f 100644
> --- a/drivers/parisc/ccio-dma.c
> +++ b/drivers/parisc/ccio-dma.c
> @@ -110,6 +110,8 @@
>  #define CMD_TLB_DIRECT_WRITE 35         /* IO_COMMAND for I/O TLB Writes     */
>  #define CMD_TLB_PURGE        33         /* IO_COMMAND to Purge I/O TLB entry */
>  
> +#define CCIO_MAPPING_ERROR    (~(dma_addr_t)0)
> +
>  struct ioa_registers {
>          /* Runway Supervisory Set */
>          int32_t    unused1[12];
> @@ -742,7 +744,7 @@ ccio_map_single(struct device *dev, void *addr, size_t size,
>  	BUG_ON(!dev);
>  	ioc = GET_IOC(dev);
>  	if (!ioc)
> -		return DMA_ERROR_CODE;
> +		return CCIO_MAPPING_ERROR;
>  
>  	BUG_ON(size <= 0);
>  
> @@ -1023,6 +1025,11 @@ ccio_unmap_sg(struct device *dev, struct scatterlist *sglist, int nents,
>  	DBG_RUN_SG("%s() DONE (nents %d)\n", __func__, nents);
>  }
>  
> +static int ccio_mapping_error(struct device *dev, dma_addr_t dma_addr)
> +{
> +	return dma_addr == CCIO_MAPPING_ERROR;
> +}
> +
>  static const struct dma_map_ops ccio_ops = {
>  	.dma_supported =	ccio_dma_supported,
>  	.alloc =		ccio_alloc,
> @@ -1031,6 +1038,7 @@ static const struct dma_map_ops ccio_ops = {
>  	.unmap_page =		ccio_unmap_page,
>  	.map_sg = 		ccio_map_sg,
>  	.unmap_sg = 		ccio_unmap_sg,
> +	.mapping_error =	ccio_mapping_error,
>  };
>  
>  #ifdef CONFIG_PROC_FS
> diff --git a/drivers/parisc/sba_iommu.c b/drivers/parisc/sba_iommu.c
> index 87ad5fd6a7a2..4086f79d58d5 100644
> --- a/drivers/parisc/sba_iommu.c
> +++ b/drivers/parisc/sba_iommu.c
> @@ -93,6 +93,8 @@
>  
>  #define DEFAULT_DMA_HINT_REG	0
>  
> +#define SBA_MAPPING_ERROR    (~(dma_addr_t)0)
> +
>  struct sba_device *sba_list;
>  EXPORT_SYMBOL_GPL(sba_list);
>  
> @@ -725,7 +727,7 @@ sba_map_single(struct device *dev, void *addr, size_t size,
>  
>  	ioc = GET_IOC(dev);
>  	if (!ioc)
> -		return DMA_ERROR_CODE;
> +		return SBA_MAPPING_ERROR;
>  
>  	/* save offset bits */
>  	offset = ((dma_addr_t) (long) addr) & ~IOVP_MASK;
> @@ -1083,6 +1085,11 @@ sba_unmap_sg(struct device *dev, struct scatterlist *sglist, int nents,
>  
>  }
>  
> +static int sba_mapping_error(struct device *dev, dma_addr_t dma_addr)
> +{
> +	return dma_addr == SBA_MAPPING_ERROR;
> +}
> +
>  static const struct dma_map_ops sba_ops = {
>  	.dma_supported =	sba_dma_supported,
>  	.alloc =		sba_alloc,
> @@ -1091,6 +1098,7 @@ static const struct dma_map_ops sba_ops = {
>  	.unmap_page =		sba_unmap_page,
>  	.map_sg =		sba_map_sg,
>  	.unmap_sg =		sba_unmap_sg,
> +	.mapping_error =	sba_mapping_error,
>  };
>  
>  
>