linux-kernel - Re: [RFC PATCH] drm/komeda: fixing of DMA mapping sg segment warning

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Date:   Fri, 29 Mar 2019 16:26:41 +0000
From:   Ayan Halder <Ayan.Halder@....com>
To:     "Lowry Li (Arm Technology China)" <Lowry.Li@....com>
CC:     Liviu Dudau <Liviu.Dudau@....com>,
        "james qian wang (Arm Technology China)" <james.qian.wang@....com>,
        "maarten.lankhorst@...ux.intel.com" 
        <maarten.lankhorst@...ux.intel.com>,
        "seanpaul@...omium.org" <seanpaul@...omium.org>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        Brian Starkey <Brian.Starkey@....com>,
        "Julien Yin (Arm Technology China)" <Julien.Yin@....com>,
        "Jonathan Chai (Arm Technology China)" <Jonathan.Chai@....com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        nd <nd@....com>
Subject: Re: [RFC PATCH] drm/komeda: fixing of DMA mapping sg segment warning

On Thu, Mar 28, 2019 at 07:25:00AM +0000, Lowry Li (Arm Technology China) wrote:
> Fixing the DMA mapping sg segment warning, which shows "DMA-API: mapping
> sg segment longer than device claims to support [len=921600] [max=65536]".
> Fixed by setting the max segment size at Komeda driver.
> 
> Signed-off-by: Lowry Li <lowry.li@....com>
> ---
>  drivers/gpu/drm/arm/display/komeda/komeda_dev.c | 4 ++++
>  drivers/gpu/drm/arm/display/komeda/komeda_dev.h | 1 +
>  2 files changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_dev.c b/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> index 7f25e6a..b4902ae 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> @@ -8,6 +8,7 @@
>  #include <linux/of_device.h>
>  #include <linux/of_graph.h>
>  #include <linux/platform_device.h>
> +#include <linux/dma-iommu.h>
>  #ifdef CONFIG_DEBUG_FS
>  #include <linux/debugfs.h>
>  #include <linux/seq_file.h>
> @@ -245,6 +246,9 @@ struct komeda_dev *komeda_dev_create(struct device *dev)
>  		goto err_cleanup;
>  	}
>  
> +	dev->dma_parms = &mdev->dma_parms;
> +	dma_set_max_seg_size(dev, DMA_BIT_MASK(32));
> +
>  	err = sysfs_create_group(&dev->kobj, &komeda_sysfs_attr_group);
>  	if (err) {
>  		DRM_ERROR("create sysfs group failed.\n");
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_dev.h b/drivers/gpu/drm/arm/display/komeda/komeda_dev.h
> index 0c3e32b..d8cfa92 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_dev.h
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_dev.h
> @@ -146,6 +146,7 @@ enum {
>   */
>  struct komeda_dev {
>  	struct device *dev;
> +	struct device_dma_parameters dma_parms;
>  	u32 __iomem   *reg_base;
>  
>  	struct komeda_chip_info chip;
> -- 
Please rebase and test your patches on drm-misc-next. 
https://drm.pages.freedesktop.org/maintainer-tools/repositories.html
> 1.9.1