remove the dma_set_{max_seg_size,seg_boundary,min_align_mask} return value v2

remove the dma_set_{max_seg_size,seg_boundary,min_align_mask} return value v2

[Christoph Hellwig]

Hi all,

the above three functions can only return errors if the bus code failed
to allocate the dma_parms structure, which is a grave error that won't
get us far.  Thus remove the pointless return values, that so far have
fortunately been mostly ignored, but which the cleanup brigade now wants
to check for for no good reason.

Changes since v1:
 - fix SCSI to not call dma_set_max_seg_size and dma_set_seg_boundary
   unconditionally

Diffstat:
 drivers/accel/qaic/qaic_drv.c                         |    4 --
 drivers/dma/idma64.c                                  |    4 --
 drivers/dma/pl330.c                                   |    5 ---
 drivers/dma/qcom/bam_dma.c                            |    6 ----
 drivers/dma/sh/rcar-dmac.c                            |    4 --
 drivers/dma/ste_dma40.c                               |    6 ----
 drivers/gpu/drm/mediatek/mtk_drm_drv.c                |    6 ----
 drivers/media/common/videobuf2/videobuf2-dma-contig.c |    3 --
 drivers/media/pci/intel/ipu6/ipu6.c                   |    4 --
 drivers/mmc/host/mmci_stm32_sdmmc.c                   |    3 +-
 drivers/net/ethernet/microsoft/mana/gdma_main.c       |    6 ----
 drivers/scsi/lpfc/lpfc_init.c                         |    7 -----
 drivers/scsi/scsi_lib.c                               |   11 ++++++-
 include/linux/dma-mapping.h                           |   25 +++++++-----------
 14 files changed, 32 insertions(+), 62 deletions(-)

[PATCH 1/4] scsi: check that busses support the DMA API before setting dma parameters

[Christoph Hellwig]

We'll start throwing warnings soon when dma_set_seg_boundary and
dma_set_max_seg_size are called on devices for buses that don't fully
support the DMA API.  Prepare for that by making the calls in the SCSI
midlayer conditional.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/scsi/scsi_lib.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 3958a6d14bf457..7f0394c4492033 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1988,8 +1988,15 @@ void scsi_init_limits(struct Scsi_Host *shost, struct queue_limits *lim)
 	if (shost->no_highmem)
 		lim->features |= BLK_FEAT_BOUNCE_HIGH;
 
-	dma_set_seg_boundary(dev, shost->dma_boundary);
-	dma_set_max_seg_size(dev, shost->max_segment_size);
+	/*
+	 * Propagate the DMA formation properties to the dma-mapping layer as
+	 * a courtesy service to the LLDDs.  This needs to check that the buses
+	 * actually support the DMA API first, though.
+	 */
+	if (dev->dma_parms) {
+		dma_set_seg_boundary(dev, shost->dma_boundary);
+		dma_set_max_seg_size(dev, shost->max_segment_size);
+	}
 }
 EXPORT_SYMBOL_GPL(scsi_init_limits);
 
-- 
2.43.0

[PATCH 2/4] dma-mapping: don't return errors from dma_set_min_align_mask

[Christoph Hellwig]

A NULL dev->dma_parms indicates either a bus that is not DMA capable or
grave bug in the implementation of the bus code.

There isn't much the driver can do in terms of error handling for either
case, so just warn and continue as DMA operations will fail anyway.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
---
 include/linux/dma-mapping.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index f693aafe221f2c..cfd6bafec3f944 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -575,13 +575,12 @@ static inline unsigned int dma_get_min_align_mask(struct device *dev)
 	return 0;
 }
 
-static inline int dma_set_min_align_mask(struct device *dev,
+static inline void dma_set_min_align_mask(struct device *dev,
 		unsigned int min_align_mask)
 {
 	if (WARN_ON_ONCE(!dev->dma_parms))
-		return -EIO;
+		return;
 	dev->dma_parms->min_align_mask = min_align_mask;
-	return 0;
 }
 
 #ifndef dma_get_cache_alignment
-- 
2.43.0

[PATCH 3/4] dma-mapping: don't return errors from dma_set_seg_boundary

[Christoph Hellwig]

A NULL dev->dma_parms indicates either a bus that is not DMA capable or
grave bug in the implementation of the bus code.

There isn't much the driver can do in terms of error handling for either
case, so just warn and continue as DMA operations will fail anyway.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
---
 include/linux/dma-mapping.h | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index cfd6bafec3f944..6bd1333dbacb9b 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -559,13 +559,11 @@ static inline unsigned long dma_get_seg_boundary_nr_pages(struct device *dev,
 	return (dma_get_seg_boundary(dev) >> page_shift) + 1;
 }
 
-static inline int dma_set_seg_boundary(struct device *dev, unsigned long mask)
+static inline void dma_set_seg_boundary(struct device *dev, unsigned long mask)
 {
-	if (dev->dma_parms) {
-		dev->dma_parms->segment_boundary_mask = mask;
-		return 0;
-	}
-	return -EIO;
+	if (WARN_ON_ONCE(!dev->dma_parms))
+		return;
+	dev->dma_parms->segment_boundary_mask = mask;
 }
 
 static inline unsigned int dma_get_min_align_mask(struct device *dev)
-- 
2.43.0

[PATCH 4/4] dma-mapping: don't return errors from dma_set_max_seg_size

[Christoph Hellwig]

A NULL dev->dma_parms indicates either a bus that is not DMA capable or
grave bug in the implementation of the bus code.

There isn't much the driver can do in terms of error handling for either
case, so just warn and continue as DMA operations will fail anyway.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
---
 drivers/accel/qaic/qaic_drv.c                         |  4 +---
 drivers/dma/idma64.c                                  |  4 +---
 drivers/dma/pl330.c                                   |  5 +----
 drivers/dma/qcom/bam_dma.c                            |  6 +-----
 drivers/dma/sh/rcar-dmac.c                            |  4 +---
 drivers/dma/ste_dma40.c                               |  6 +-----
 drivers/gpu/drm/mediatek/mtk_drm_drv.c                |  6 +-----
 drivers/media/common/videobuf2/videobuf2-dma-contig.c |  3 +--
 drivers/media/pci/intel/ipu6/ipu6.c                   |  4 +---
 drivers/mmc/host/mmci_stm32_sdmmc.c                   |  3 ++-
 drivers/net/ethernet/microsoft/mana/gdma_main.c       |  6 +-----
 drivers/scsi/lpfc/lpfc_init.c                         |  7 +------
 include/linux/dma-mapping.h                           | 10 ++++------
 13 files changed, 17 insertions(+), 51 deletions(-)

diff --git a/drivers/accel/qaic/qaic_drv.c b/drivers/accel/qaic/qaic_drv.c
index 580b29ed190217..bf10156c334e71 100644
--- a/drivers/accel/qaic/qaic_drv.c
+++ b/drivers/accel/qaic/qaic_drv.c
@@ -447,9 +447,7 @@ static int init_pci(struct qaic_device *qdev, struct pci_dev *pdev)
 	ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
 	if (ret)
 		return ret;
-	ret = dma_set_max_seg_size(&pdev->dev, UINT_MAX);
-	if (ret)
-		return ret;
+	dma_set_max_seg_size(&pdev->dev, UINT_MAX);
 
 	qdev->bar_0 = devm_ioremap_resource(&pdev->dev, &pdev->resource[0]);
 	if (IS_ERR(qdev->bar_0))
diff --git a/drivers/dma/idma64.c b/drivers/dma/idma64.c
index e3505e56784b1a..1398814d8fbb63 100644
--- a/drivers/dma/idma64.c
+++ b/drivers/dma/idma64.c
@@ -598,9 +598,7 @@ static int idma64_probe(struct idma64_chip *chip)
 
 	idma64->dma.dev = chip->sysdev;
 
-	ret = dma_set_max_seg_size(idma64->dma.dev, IDMA64C_CTLH_BLOCK_TS_MASK);
-	if (ret)
-		return ret;
+	dma_set_max_seg_size(idma64->dma.dev, IDMA64C_CTLH_BLOCK_TS_MASK);
 
 	ret = dma_async_device_register(&idma64->dma);
 	if (ret)
diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index 60c4de8dac1d2a..82a9fe88ad54c9 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -3163,10 +3163,7 @@ pl330_probe(struct amba_device *adev, const struct amba_id *id)
 	 * This is the limit for transfers with a buswidth of 1, larger
 	 * buswidths will have larger limits.
 	 */
-	ret = dma_set_max_seg_size(&adev->dev, 1900800);
-	if (ret)
-		dev_err(&adev->dev, "unable to set the seg size\n");
-
+	dma_set_max_seg_size(&adev->dev, 1900800);
 
 	init_pl330_debugfs(pl330);
 	dev_info(&adev->dev,
diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
index 5e7d332731e0c1..368ffaa4003789 100644
--- a/drivers/dma/qcom/bam_dma.c
+++ b/drivers/dma/qcom/bam_dma.c
@@ -1325,11 +1325,7 @@ static int bam_dma_probe(struct platform_device *pdev)
 
 	/* set max dma segment size */
 	bdev->common.dev = bdev->dev;
-	ret = dma_set_max_seg_size(bdev->common.dev, BAM_FIFO_SIZE);
-	if (ret) {
-		dev_err(bdev->dev, "cannot set maximum segment size\n");
-		goto err_bam_channel_exit;
-	}
+	dma_set_max_seg_size(bdev->common.dev, BAM_FIFO_SIZE);
 
 	platform_set_drvdata(pdev, bdev);
 
diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index 40482cb73d798a..1094a2f821649c 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -1868,9 +1868,7 @@ static int rcar_dmac_probe(struct platform_device *pdev)
 
 	dmac->dev = &pdev->dev;
 	platform_set_drvdata(pdev, dmac);
-	ret = dma_set_max_seg_size(dmac->dev, RCAR_DMATCR_MASK);
-	if (ret)
-		return ret;
+	dma_set_max_seg_size(dmac->dev, RCAR_DMATCR_MASK);
 
 	ret = dma_set_mask_and_coherent(dmac->dev, DMA_BIT_MASK(40));
 	if (ret)
diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c
index 2c489299148eee..d52e1685aed53f 100644
--- a/drivers/dma/ste_dma40.c
+++ b/drivers/dma/ste_dma40.c
@@ -3632,11 +3632,7 @@ static int __init d40_probe(struct platform_device *pdev)
 	if (ret)
 		goto destroy_cache;
 
-	ret = dma_set_max_seg_size(base->dev, STEDMA40_MAX_SEG_SIZE);
-	if (ret) {
-		d40_err(dev, "Failed to set dma max seg size\n");
-		goto destroy_cache;
-	}
+	dma_set_max_seg_size(base->dev, STEDMA40_MAX_SEG_SIZE);
 
 	d40_hw_init(base);
 
diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index 77b50c56c124ce..3e807195a0d03a 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -559,11 +559,7 @@ static int mtk_drm_kms_init(struct drm_device *drm)
 	 * Configure the DMA segment size to make sure we get contiguous IOVA
 	 * when importing PRIME buffers.
 	 */
-	ret = dma_set_max_seg_size(dma_dev, UINT_MAX);
-	if (ret) {
-		dev_err(dma_dev, "Failed to set DMA segment size\n");
-		goto err_component_unbind;
-	}
+	dma_set_max_seg_size(dma_dev, UINT_MAX);
 
 	ret = drm_vblank_init(drm, MAX_CRTC);
 	if (ret < 0)
diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
index 3d4fd4ef53107c..bb0b7fa67b539a 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
@@ -854,8 +854,7 @@ int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size)
 		return -ENODEV;
 	}
 	if (dma_get_max_seg_size(dev) < size)
-		return dma_set_max_seg_size(dev, size);
-
+		dma_set_max_seg_size(dev, size);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(vb2_dma_contig_set_max_seg_size);
diff --git a/drivers/media/pci/intel/ipu6/ipu6.c b/drivers/media/pci/intel/ipu6/ipu6.c
index bbd646378ab3ed..83e70c692d957f 100644
--- a/drivers/media/pci/intel/ipu6/ipu6.c
+++ b/drivers/media/pci/intel/ipu6/ipu6.c
@@ -576,9 +576,7 @@ static int ipu6_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	if (ret)
 		return dev_err_probe(dev, ret, "Failed to set DMA mask\n");
 
-	ret = dma_set_max_seg_size(dev, UINT_MAX);
-	if (ret)
-		return dev_err_probe(dev, ret, "Failed to set max_seg_size\n");
+	dma_set_max_seg_size(dev, UINT_MAX);
 
 	ret = ipu6_pci_config_setup(pdev, isp->hw_ver);
 	if (ret)
diff --git a/drivers/mmc/host/mmci_stm32_sdmmc.c b/drivers/mmc/host/mmci_stm32_sdmmc.c
index f5da7f9baa52d4..9dc51859c2e51e 100644
--- a/drivers/mmc/host/mmci_stm32_sdmmc.c
+++ b/drivers/mmc/host/mmci_stm32_sdmmc.c
@@ -213,7 +213,8 @@ static int sdmmc_idma_setup(struct mmci_host *host)
 		host->mmc->max_seg_size = host->mmc->max_req_size;
 	}
 
-	return dma_set_max_seg_size(dev, host->mmc->max_seg_size);
+	dma_set_max_seg_size(dev, host->mmc->max_seg_size);
+	return 0;
 }
 
 static int sdmmc_idma_start(struct mmci_host *host, unsigned int *datactrl)
diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
index ddb8f68d80a206..ca4ed58f1206dd 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -1496,11 +1496,7 @@ static int mana_gd_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	if (err)
 		goto release_region;
 
-	err = dma_set_max_seg_size(&pdev->dev, UINT_MAX);
-	if (err) {
-		dev_err(&pdev->dev, "Failed to set dma device segment size\n");
-		goto release_region;
-	}
+	dma_set_max_seg_size(&pdev->dev, UINT_MAX);
 
 	err = -ENOMEM;
 	gc = vzalloc(sizeof(*gc));
diff --git a/drivers/scsi/lpfc/lpfc_init.c b/drivers/scsi/lpfc/lpfc_init.c
index e1dfa96c2a553a..50620918becd59 100644
--- a/drivers/scsi/lpfc/lpfc_init.c
+++ b/drivers/scsi/lpfc/lpfc_init.c
@@ -13861,12 +13861,7 @@ lpfc_get_sli4_parameters(struct lpfc_hba *phba, LPFC_MBOXQ_t *mboxq)
 	if (sli4_params->sge_supp_len > LPFC_MAX_SGE_SIZE)
 		sli4_params->sge_supp_len = LPFC_MAX_SGE_SIZE;
 
-	rc = dma_set_max_seg_size(&phba->pcidev->dev, sli4_params->sge_supp_len);
-	if (unlikely(rc)) {
-		lpfc_printf_log(phba, KERN_INFO, LOG_INIT,
-				"6400 Can't set dma maximum segment size\n");
-		return rc;
-	}
+	dma_set_max_seg_size(&phba->pcidev->dev, sli4_params->sge_supp_len);
 
 	/*
 	 * Check whether the adapter supports an embedded copy of the
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 6bd1333dbacb9b..1524da363734af 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -524,13 +524,11 @@ static inline unsigned int dma_get_max_seg_size(struct device *dev)
 	return SZ_64K;
 }
 
-static inline int dma_set_max_seg_size(struct device *dev, unsigned int size)
+static inline void dma_set_max_seg_size(struct device *dev, unsigned int size)
 {
-	if (dev->dma_parms) {
-		dev->dma_parms->max_segment_size = size;
-		return 0;
-	}
-	return -EIO;
+	if (WARN_ON_ONCE(!dev->dma_parms))
+		return;
+	dev->dma_parms->max_segment_size = size;
 }
 
 static inline unsigned long dma_get_seg_boundary(struct device *dev)
-- 
2.43.0

Re: [PATCH 4/4] dma-mapping: don't return errors from dma_set_max_seg_size

[Ulf Hansson]

On Sat, 24 Aug 2024 at 05:51, Christoph Hellwig <hch@lst.de> wrote:
>
> A NULL dev->dma_parms indicates either a bus that is not DMA capable or
> grave bug in the implementation of the bus code.
>
> There isn't much the driver can do in terms of error handling for either
> case, so just warn and continue as DMA operations will fail anyway.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> ---
>  drivers/accel/qaic/qaic_drv.c                         |  4 +---
>  drivers/dma/idma64.c                                  |  4 +---
>  drivers/dma/pl330.c                                   |  5 +----
>  drivers/dma/qcom/bam_dma.c                            |  6 +-----
>  drivers/dma/sh/rcar-dmac.c                            |  4 +---
>  drivers/dma/ste_dma40.c                               |  6 +-----
>  drivers/gpu/drm/mediatek/mtk_drm_drv.c                |  6 +-----
>  drivers/media/common/videobuf2/videobuf2-dma-contig.c |  3 +--
>  drivers/media/pci/intel/ipu6/ipu6.c                   |  4 +---
>  drivers/mmc/host/mmci_stm32_sdmmc.c                   |  3 ++-
>  drivers/net/ethernet/microsoft/mana/gdma_main.c       |  6 +-----
>  drivers/scsi/lpfc/lpfc_init.c                         |  7 +------
>  include/linux/dma-mapping.h                           | 10 ++++------
>  13 files changed, 17 insertions(+), 51 deletions(-)

Acked-by: Ulf Hansson <ulf.hansson@linaro.org> # For MMC

Kind regards
Uffe

>
> diff --git a/drivers/accel/qaic/qaic_drv.c b/drivers/accel/qaic/qaic_drv.c
> index 580b29ed190217..bf10156c334e71 100644
> --- a/drivers/accel/qaic/qaic_drv.c
> +++ b/drivers/accel/qaic/qaic_drv.c
> @@ -447,9 +447,7 @@ static int init_pci(struct qaic_device *qdev, struct pci_dev *pdev)
>         ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
>         if (ret)
>                 return ret;
> -       ret = dma_set_max_seg_size(&pdev->dev, UINT_MAX);
> -       if (ret)
> -               return ret;
> +       dma_set_max_seg_size(&pdev->dev, UINT_MAX);
>
>         qdev->bar_0 = devm_ioremap_resource(&pdev->dev, &pdev->resource[0]);
>         if (IS_ERR(qdev->bar_0))
> diff --git a/drivers/dma/idma64.c b/drivers/dma/idma64.c
> index e3505e56784b1a..1398814d8fbb63 100644
> --- a/drivers/dma/idma64.c
> +++ b/drivers/dma/idma64.c
> @@ -598,9 +598,7 @@ static int idma64_probe(struct idma64_chip *chip)
>
>         idma64->dma.dev = chip->sysdev;
>
> -       ret = dma_set_max_seg_size(idma64->dma.dev, IDMA64C_CTLH_BLOCK_TS_MASK);
> -       if (ret)
> -               return ret;
> +       dma_set_max_seg_size(idma64->dma.dev, IDMA64C_CTLH_BLOCK_TS_MASK);
>
>         ret = dma_async_device_register(&idma64->dma);
>         if (ret)
> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> index 60c4de8dac1d2a..82a9fe88ad54c9 100644
> --- a/drivers/dma/pl330.c
> +++ b/drivers/dma/pl330.c
> @@ -3163,10 +3163,7 @@ pl330_probe(struct amba_device *adev, const struct amba_id *id)
>          * This is the limit for transfers with a buswidth of 1, larger
>          * buswidths will have larger limits.
>          */
> -       ret = dma_set_max_seg_size(&adev->dev, 1900800);
> -       if (ret)
> -               dev_err(&adev->dev, "unable to set the seg size\n");
> -
> +       dma_set_max_seg_size(&adev->dev, 1900800);
>
>         init_pl330_debugfs(pl330);
>         dev_info(&adev->dev,
> diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
> index 5e7d332731e0c1..368ffaa4003789 100644
> --- a/drivers/dma/qcom/bam_dma.c
> +++ b/drivers/dma/qcom/bam_dma.c
> @@ -1325,11 +1325,7 @@ static int bam_dma_probe(struct platform_device *pdev)
>
>         /* set max dma segment size */
>         bdev->common.dev = bdev->dev;
> -       ret = dma_set_max_seg_size(bdev->common.dev, BAM_FIFO_SIZE);
> -       if (ret) {
> -               dev_err(bdev->dev, "cannot set maximum segment size\n");
> -               goto err_bam_channel_exit;
> -       }
> +       dma_set_max_seg_size(bdev->common.dev, BAM_FIFO_SIZE);
>
>         platform_set_drvdata(pdev, bdev);
>
> diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
> index 40482cb73d798a..1094a2f821649c 100644
> --- a/drivers/dma/sh/rcar-dmac.c
> +++ b/drivers/dma/sh/rcar-dmac.c
> @@ -1868,9 +1868,7 @@ static int rcar_dmac_probe(struct platform_device *pdev)
>
>         dmac->dev = &pdev->dev;
>         platform_set_drvdata(pdev, dmac);
> -       ret = dma_set_max_seg_size(dmac->dev, RCAR_DMATCR_MASK);
> -       if (ret)
> -               return ret;
> +       dma_set_max_seg_size(dmac->dev, RCAR_DMATCR_MASK);
>
>         ret = dma_set_mask_and_coherent(dmac->dev, DMA_BIT_MASK(40));
>         if (ret)
> diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c
> index 2c489299148eee..d52e1685aed53f 100644
> --- a/drivers/dma/ste_dma40.c
> +++ b/drivers/dma/ste_dma40.c
> @@ -3632,11 +3632,7 @@ static int __init d40_probe(struct platform_device *pdev)
>         if (ret)
>                 goto destroy_cache;
>
> -       ret = dma_set_max_seg_size(base->dev, STEDMA40_MAX_SEG_SIZE);
> -       if (ret) {
> -               d40_err(dev, "Failed to set dma max seg size\n");
> -               goto destroy_cache;
> -       }
> +       dma_set_max_seg_size(base->dev, STEDMA40_MAX_SEG_SIZE);
>
>         d40_hw_init(base);
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> index 77b50c56c124ce..3e807195a0d03a 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> @@ -559,11 +559,7 @@ static int mtk_drm_kms_init(struct drm_device *drm)
>          * Configure the DMA segment size to make sure we get contiguous IOVA
>          * when importing PRIME buffers.
>          */
> -       ret = dma_set_max_seg_size(dma_dev, UINT_MAX);
> -       if (ret) {
> -               dev_err(dma_dev, "Failed to set DMA segment size\n");
> -               goto err_component_unbind;
> -       }
> +       dma_set_max_seg_size(dma_dev, UINT_MAX);
>
>         ret = drm_vblank_init(drm, MAX_CRTC);
>         if (ret < 0)
> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> index 3d4fd4ef53107c..bb0b7fa67b539a 100644
> --- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> +++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> @@ -854,8 +854,7 @@ int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size)
>                 return -ENODEV;
>         }
>         if (dma_get_max_seg_size(dev) < size)
> -               return dma_set_max_seg_size(dev, size);
> -
> +               dma_set_max_seg_size(dev, size);
>         return 0;
>  }
>  EXPORT_SYMBOL_GPL(vb2_dma_contig_set_max_seg_size);
> diff --git a/drivers/media/pci/intel/ipu6/ipu6.c b/drivers/media/pci/intel/ipu6/ipu6.c
> index bbd646378ab3ed..83e70c692d957f 100644
> --- a/drivers/media/pci/intel/ipu6/ipu6.c
> +++ b/drivers/media/pci/intel/ipu6/ipu6.c
> @@ -576,9 +576,7 @@ static int ipu6_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>         if (ret)
>                 return dev_err_probe(dev, ret, "Failed to set DMA mask\n");
>
> -       ret = dma_set_max_seg_size(dev, UINT_MAX);
> -       if (ret)
> -               return dev_err_probe(dev, ret, "Failed to set max_seg_size\n");
> +       dma_set_max_seg_size(dev, UINT_MAX);
>
>         ret = ipu6_pci_config_setup(pdev, isp->hw_ver);
>         if (ret)
> diff --git a/drivers/mmc/host/mmci_stm32_sdmmc.c b/drivers/mmc/host/mmci_stm32_sdmmc.c
> index f5da7f9baa52d4..9dc51859c2e51e 100644
> --- a/drivers/mmc/host/mmci_stm32_sdmmc.c
> +++ b/drivers/mmc/host/mmci_stm32_sdmmc.c
> @@ -213,7 +213,8 @@ static int sdmmc_idma_setup(struct mmci_host *host)
>                 host->mmc->max_seg_size = host->mmc->max_req_size;
>         }
>
> -       return dma_set_max_seg_size(dev, host->mmc->max_seg_size);
> +       dma_set_max_seg_size(dev, host->mmc->max_seg_size);
> +       return 0;
>  }
>
>  static int sdmmc_idma_start(struct mmci_host *host, unsigned int *datactrl)
> diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> index ddb8f68d80a206..ca4ed58f1206dd 100644
> --- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
> +++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> @@ -1496,11 +1496,7 @@ static int mana_gd_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>         if (err)
>                 goto release_region;
>
> -       err = dma_set_max_seg_size(&pdev->dev, UINT_MAX);
> -       if (err) {
> -               dev_err(&pdev->dev, "Failed to set dma device segment size\n");
> -               goto release_region;
> -       }
> +       dma_set_max_seg_size(&pdev->dev, UINT_MAX);
>
>         err = -ENOMEM;
>         gc = vzalloc(sizeof(*gc));
> diff --git a/drivers/scsi/lpfc/lpfc_init.c b/drivers/scsi/lpfc/lpfc_init.c
> index e1dfa96c2a553a..50620918becd59 100644
> --- a/drivers/scsi/lpfc/lpfc_init.c
> +++ b/drivers/scsi/lpfc/lpfc_init.c
> @@ -13861,12 +13861,7 @@ lpfc_get_sli4_parameters(struct lpfc_hba *phba, LPFC_MBOXQ_t *mboxq)
>         if (sli4_params->sge_supp_len > LPFC_MAX_SGE_SIZE)
>                 sli4_params->sge_supp_len = LPFC_MAX_SGE_SIZE;
>
> -       rc = dma_set_max_seg_size(&phba->pcidev->dev, sli4_params->sge_supp_len);
> -       if (unlikely(rc)) {
> -               lpfc_printf_log(phba, KERN_INFO, LOG_INIT,
> -                               "6400 Can't set dma maximum segment size\n");
> -               return rc;
> -       }
> +       dma_set_max_seg_size(&phba->pcidev->dev, sli4_params->sge_supp_len);
>
>         /*
>          * Check whether the adapter supports an embedded copy of the
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index 6bd1333dbacb9b..1524da363734af 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -524,13 +524,11 @@ static inline unsigned int dma_get_max_seg_size(struct device *dev)
>         return SZ_64K;
>  }
>
> -static inline int dma_set_max_seg_size(struct device *dev, unsigned int size)
> +static inline void dma_set_max_seg_size(struct device *dev, unsigned int size)
>  {
> -       if (dev->dma_parms) {
> -               dev->dma_parms->max_segment_size = size;
> -               return 0;
> -       }
> -       return -EIO;
> +       if (WARN_ON_ONCE(!dev->dma_parms))
> +               return;
> +       dev->dma_parms->max_segment_size = size;
>  }
>
>  static inline unsigned long dma_get_seg_boundary(struct device *dev)
> --
> 2.43.0
>
>

Re: [PATCH 1/4] scsi: check that busses support the DMA API before setting dma parameters

[Robin Murphy]

On 24/08/2024 4:49 am, Christoph Hellwig wrote:
> We'll start throwing warnings soon when dma_set_seg_boundary and
> dma_set_max_seg_size are called on devices for buses that don't fully
> support the DMA API.  Prepare for that by making the calls in the SCSI
> midlayer conditional.

Just thinking ahead, might it be worth a logical "are SG segment limits 
relevant?" wrapper around the dev->dma_parms reference? Not a big deal 
for now if we think this site is the only user, so either way,

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   drivers/scsi/scsi_lib.c | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 3958a6d14bf457..7f0394c4492033 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1988,8 +1988,15 @@ void scsi_init_limits(struct Scsi_Host *shost, struct queue_limits *lim)
>   	if (shost->no_highmem)
>   		lim->features |= BLK_FEAT_BOUNCE_HIGH;
>   
> -	dma_set_seg_boundary(dev, shost->dma_boundary);
> -	dma_set_max_seg_size(dev, shost->max_segment_size);
> +	/*
> +	 * Propagate the DMA formation properties to the dma-mapping layer as
> +	 * a courtesy service to the LLDDs.  This needs to check that the buses
> +	 * actually support the DMA API first, though.
> +	 */
> +	if (dev->dma_parms) {
> +		dma_set_seg_boundary(dev, shost->dma_boundary);
> +		dma_set_max_seg_size(dev, shost->max_segment_size);
> +	}
>   }
>   EXPORT_SYMBOL_GPL(scsi_init_limits);
>   

Re: remove the dma_set_{max_seg_size,seg_boundary,min_align_mask} return value v2

[Martin K. Petersen]

Christoph,

> the above three functions can only return errors if the bus code
> failed to allocate the dma_parms structure, which is a grave error
> that won't get us far. Thus remove the pointless return values, that
> so far have fortunately been mostly ignored, but which the cleanup
> brigade now wants to check for for no good reason.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: remove the dma_set_{max_seg_size,seg_boundary,min_align_mask} return value v2

[Christoph Hellwig]

Thanks,

I've pulled the series into the dma-mapping for-next tree now.