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[222.155.0.244]) by smtp.gmail.com with ESMTPSA id 13-20020a17090a08cd00b001ec932d7592sm8040238pjn.9.2022.06.27.20.26.00 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 27 Jun 2022 20:26:10 -0700 (PDT) Subject: Re: [PATCH v2 3/3] arch/*/: remove CONFIG_VIRT_TO_BUS To: Geert Uytterhoeven References: <20220617125750.728590-1-arnd@kernel.org> <20220617125750.728590-4-arnd@kernel.org> <6ba86afe-bf9f-1aca-7af1-d0d348d75ffc@gmail.com> Cc: Arnd Bergmann , scsi , Linux Kernel Mailing List , Arnd Bergmann , Jakub Kicinski , Christoph Hellwig , Marek Szyprowski , Robin Murphy , Linux IOMMU , Khalid Aziz , "Maciej W . Rozycki" , Matt Wang , Miquel van Smoorenburg , Mark Salyzyn , linuxppc-dev , Linux-Arch , alpha , linux-m68k , Parisc List , Denis Efremov , Michael Ellerman From: Michael Schmitz Message-ID: <9289fd82-285c-035f-5355-4d70ce4f87b0@gmail.com> Date: Tue, 28 Jun 2022 15:25:58 +1200 User-Agent: Mozilla/5.0 (X11; Linux ppc; rv:45.0) Gecko/20100101 Icedove/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/mixed; boundary="------------EF1F8A9B021AD1B88577153E" Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org This is a multi-part message in MIME format. --------------EF1F8A9B021AD1B88577153E Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Hii Geert Am 28.06.2022 um 09:12 schrieb Michael Schmitz: > Hi Geert, > > On 27/06/22 20:26, Geert Uytterhoeven wrote: >> Hi Michael, >> >> On Sat, Jun 18, 2022 at 3:06 AM Michael Schmitz >> wrote: >>> Am 18.06.2022 um 00:57 schrieb Arnd Bergmann: >>>> From: Arnd Bergmann >>>> >>>> All architecture-independent users of virt_to_bus() and bus_to_virt() >>>> have been fixed to use the dma mapping interfaces or have been >>>> removed now. This means the definitions on most architectures, and the >>>> CONFIG_VIRT_TO_BUS symbol are now obsolete and can be removed. >>>> >>>> The only exceptions to this are a few network and scsi drivers for m68k >>>> Amiga and VME machines and ppc32 Macintosh. These drivers work >>>> correctly >>>> with the old interfaces and are probably not worth changing. >>> The Amiga SCSI drivers are all old WD33C93 ones, and replacing >>> virt_to_bus by virt_to_phys in the dma_setup() function there would >>> cause no functional change at all. >> FTR, the sgiwd93 driver use dma_map_single(). > > Thanks! From what I see, it doesn't have to deal with bounce buffers > though? Leaving the bounce buffer handling in place, and taking a few other liberties - this is what converting the easiest case (a3000 SCSI) might look like. Any obvious mistakes? The mvme147 driver would be very similar to handle (after conversion to a platform device). The driver allocates bounce buffers using kmalloc if it hits an unaligned data buffer - can such buffers still even happen these days? If I understand dma_map_single() correctly, the resulting dma handle would be equally misaligned? To allocate a bounce buffer, would it be OK to use dma_alloc_coherent() even though AFAIU memory used for DMA buffers generally isn't consistent on m68k? Thinking ahead to the other two Amiga drivers - I wonder whether allocating a static bounce buffer or a DMA pool at driver init is likely to succeed if the kernel runs from the low 16 MB RAM chunk? It certainly won't succeed if the kernel runs from a higher memory address, so the present bounce buffer logic around amiga_chip_alloc() might still need to be used here. Leaves the question whether converting the gvp11 and a2091 drivers is actually worth it, if bounce buffers still have to be handled explicitly. Untested (except for compile testing), un-checkpatched, don't try this on any disk with valuable data ... Cheers, Michael --------------EF1F8A9B021AD1B88577153E Content-Type: text/x-diff; name="0001-scsi-convert-m68k-WD33C93-drivers-to-DMA-API.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="0001-scsi-convert-m68k-WD33C93-drivers-to-DMA-API.patch" >From e8c6aa068d27901c49dfb7442d4200cc966350a5 Mon Sep 17 00:00:00 2001 From: Michael Schmitz Date: Tue, 28 Jun 2022 12:45:08 +1200 Subject: [PATCH] scsi - convert m68k WD33C93 drivers to DMA API Use dma_map_single() for gvp11 driver (leave bounce buffer logic unchanged). Compile-tested only. Signed-off-by: Michael Schmitz --- drivers/scsi/a3000.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/a3000.c b/drivers/scsi/a3000.c index dd161885eed1..3c62e8bafb8f 100644 --- a/drivers/scsi/a3000.c +++ b/drivers/scsi/a3000.c @@ -7,6 +7,7 @@ #include #include #include +#include #include #include @@ -25,8 +26,11 @@ struct a3000_hostdata { struct WD33C93_hostdata wh; struct a3000_scsiregs *regs; + struct device *dev; }; +#define DMA_DIR(d) ((d == DATA_OUT_DIR) ? DMA_TO_DEVICE : DMA_FROM_DEVICE) + static irqreturn_t a3000_intr(int irq, void *data) { struct Scsi_Host *instance = data; @@ -49,12 +53,16 @@ static irqreturn_t a3000_intr(int irq, void *data) static int dma_setup(struct scsi_cmnd *cmd, int dir_in) { struct scsi_pointer *scsi_pointer = WD33C93_scsi_pointer(cmd); + unsigned long len = scsi_pointer->this_residual; struct Scsi_Host *instance = cmd->device->host; struct a3000_hostdata *hdata = shost_priv(instance); struct WD33C93_hostdata *wh = &hdata->wh; struct a3000_scsiregs *regs = hdata->regs; unsigned short cntr = CNTR_PDMD | CNTR_INTEN; - unsigned long addr = virt_to_bus(scsi_pointer->ptr); + dma_addr_t addr; + + addr = dma_map_single(hdata->dev, scsi_pointer->ptr, len, DMA_DIR(dir_in)); + scsi_pointer->dma_handle = addr; /* * if the physical address has the wrong alignment, or if @@ -79,7 +87,7 @@ static int dma_setup(struct scsi_cmnd *cmd, int dir_in) scsi_pointer->this_residual); } - addr = virt_to_bus(wh->dma_bounce_buffer); + addr = virt_to_phys(wh->dma_bounce_buffer); } /* setup dma direction */ @@ -166,6 +174,10 @@ static void dma_stop(struct Scsi_Host *instance, struct scsi_cmnd *SCpnt, wh->dma_bounce_len = 0; } } + dma_unmap_single(hdata->dev, scsi_pointer->dma_handle, + scsi_pointer->this_residual, + DMA_DIR(wh->dma_dir)); + } static struct scsi_host_template amiga_a3000_scsi_template = { @@ -193,6 +205,11 @@ static int __init amiga_a3000_scsi_probe(struct platform_device *pdev) wd33c93_regs wdregs; struct a3000_hostdata *hdata; + if (dma_set_mask(&pdev->dev, DMA_BIT_MASK(32))) { + dev_warn(&pdev->dev, "cannot use 32 bit DMA\n"); + return -ENODEV; + } + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); if (!res) return -ENODEV; @@ -216,6 +233,7 @@ static int __init amiga_a3000_scsi_probe(struct platform_device *pdev) wdregs.SCMD = ®s->SCMD; hdata = shost_priv(instance); + hdata->dev = &pdev->dev; hdata->wh.no_sync = 0xff; hdata->wh.fast = 0; hdata->wh.dma_mode = CTRL_DMA; -- 2.17.1 --------------EF1F8A9B021AD1B88577153E--