sata_dwc_460ex build failures in -next

[andriy.shevchenko@linux.intel.com (Andy Shevchenko)]

On Mon, 2015-01-12 at 12:50 +0000, Russell King - ARM Linux wrote:
> On Mon, Jan 12, 2015 at 12:36:55PM +0000, Mark Brown wrote:
> > On Mon, Jan 12, 2015 at 08:03:27AM +0000, Build bot for Mark Brown wrote:
> > 
> > > 	arm64-allmodconfig
> > > ../drivers/ata/sata_dwc_460ex.c:719:3: error: implicit declaration of function 'dma_cache_sync' [-Werror=implicit-function-declaration]
> > > 
> > > 	arm-allmodconfig
> > > ../drivers/ata/sata_dwc_460ex.c:719:3: error: implicit declaration of function 'dma_cache_sync' [-Werror=implicit-function-declaration]
> > 
> > Since commit 84683a7e081ff60e (sata_dwc_460ex: enable COMPILE_TEST for
> > the driver) the sata_dwc_460ex has been breaking the all*config builds
> > for arm and arm64 as the driver uses dma_cache_sync() but this function
> > is not provided on those architectures.
> > 
> > Either a more specific dependency is needed or the function shouldn't be
> > used, I've not looked at the code.
> 
> The driver does look rather broken.  Let's first read up when dma_cache_sync()
> should be used:
> 
>   void
>   dma_cache_sync(struct device *dev, void *vaddr, size_t size,
>                  enum dma_data_direction direction)
>   
>   Do a partial sync of memory that was allocated by
>   dma_alloc_noncoherent(), starting at virtual address vaddr and
>   continuing on for size.  Again, you *must* observe the cache line
>   boundaries when doing this.
> 
> Note "memory that was allocated by dma_alloc_noncoherent()".
> 
> Now, let's look at the driver:
> 
> static int map_sg_to_lli(struct scatterlist *sg, int num_elems,
>                         struct lli *lli, dma_addr_t dma_lli,
>                         void __iomem *dmadr_addr, int dir)
> {
> ...
>                 dma_cache_sync(NULL, lli, (sizeof(struct lli) * idx),
>                                DMA_BIDIRECTIONAL);
> }
> 
> static int dma_dwc_xfer_setup(struct scatterlist *sg, int num_elems,
>                               struct lli *lli, dma_addr_t dma_lli,
>                               void __iomem *addr, int dir)
> {
>         /* Convert SG list to linked list of items (LLIs) for AHB DMA */
>         num_lli = map_sg_to_lli(sg, num_elems, lli, dma_lli, addr, dir);
> }
> 
>         dma_chan = dma_dwc_xfer_setup(sg, qc->n_elem, hsdevp->llit[tag],
>                                       hsdevp->llit_dma[tag],
>                                       (void *__iomem)(&hsdev->sata_dwc_regs->\
>                                       dmadr), qc->dma_dir);
> 
>         for (i = 0; i < SATA_DWC_QCMD_MAX; i++) {
>                 hsdevp->llit[i] = dma_alloc_coherent(pdev,
>                                                      SATA_DWC_DMAC_LLI_TBL_SZ,
>                                                      &(hsdevp->llit_dma[i]),
>                                                      GFP_ATOMIC);
> 
> So, hsdevp->llit[x] is allocated using dma_alloc_*coherent*(), not
> dma_alloc_*noncohernet*(), so dma_cache_sync() should not be used
> according to the DMA API documentation.
> 
> Moreover, that GFP_ATOMIC flag looks mightily suspicious - we've done
> a previous allocation using kzalloc(, GFP_KERNEL), so we aren't in an
> atomic region, so why use GFP_ATOMIC there?
> 
> It doesn't look like it'll pass sparse checks either:
> 
> struct sata_dwc_device {
>         u8                      *reg_base;
>         struct sata_dwc_regs    *sata_dwc_regs; /* DW Synopsys SATA specific */
> };
> 
>         u8 *base = NULL;
> 
>         base = of_iomap(ofdev->dev.of_node, 0);
>         hsdev->reg_base = base;
>         hsdev->sata_dwc_regs = (void *__iomem)(base + SATA_DWC_REG_OFFSET);
> 
> Maybe it should be moved to drivers/staging? :)

I'm working on it.

My target is to remove private implementation of dw_dmac from this
driver. It will make it mostly free of sparse / compiler warnings.
Sorry, I didn't test on ARM platform since I have none.

I just send a plug patch to disable compilation on ARMs.


-- 
Andy Shevchenko <andriy.shevchenko@intel.com>
Intel Finland Oy