[PATCH] drm: etnaviv: avoid DMA API warning when importing buffers

Mon Feb 25 10:54:24 UTC 2019

On Mon, Feb 25, 2019 at 10:51:30AM +0000, Russell King wrote:
> During boot, I get this kernel warning:
> 
> WARNING: CPU: 0 PID: 19001 at kernel/dma/debug.c:1301 debug_dma_map_sg+0x284/0x3dc
> etnaviv etnaviv: DMA-API: mapping sg segment longer than device claims to support [len=3145728] [max=65536]
> Modules linked in: ip6t_REJECT nf_reject_ipv6 ip6t_rpfilter xt_tcpudp ipt_REJECT nf_reject_ipv4 xt_conntrack ip_set nfnetlink ebtable_broute ebtable_nat ip6table_raw ip6table_nat nf_nat_ipv6 ip6table_mangle iptable_raw iptable_nat nf_nat_ipv4 nf_nat nf_conntrack nf_defrag_ipv4 nf_defrag_ipv6 libcrc32c iptable_mangle ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter caam_jr error snd_soc_imx_spdif imx_thermal snd_soc_imx_audmux nvmem_imx_ocotp snd_soc_sgtl5000
> caam imx_sdma virt_dma coda rc_cec v4l2_mem2mem snd_soc_fsl_ssi snd_soc_fsl_spdif imx_vdoa imx_pcm_dma videobuf2_dma_contig etnaviv dw_hdmi_cec gpu_sched dw_hdmi_ahb_audio imx6q_cpufreq nfsd sch_fq_codel ip_tables x_tables
> CPU: 0 PID: 19001 Comm: Xorg Not tainted 4.20.0+ #307
> Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
> [<c0019658>] (unwind_backtrace) from [<c001489c>] (show_stack+0x10/0x14)
> [<c001489c>] (show_stack) from [<c07fb420>] (dump_stack+0x9c/0xd4)
> [<c07fb420>] (dump_stack) from [<c00312dc>] (__warn+0xf8/0x124)
> [<c00312dc>] (__warn) from [<c00313d0>] (warn_slowpath_fmt+0x38/0x48)
> [<c00313d0>] (warn_slowpath_fmt) from [<c00b14e8>] (debug_dma_map_sg+0x284/0x3dc)
> [<c00b14e8>] (debug_dma_map_sg) from [<c046eb40>] (drm_gem_map_dma_buf+0xc4/0x13c)
> [<c046eb40>] (drm_gem_map_dma_buf) from [<c04c3314>] (dma_buf_map_attachment+0x38/0x5c)
> [<c04c3314>] (dma_buf_map_attachment) from [<c046e728>] (drm_gem_prime_import_dev+0x74/0x104)
> [<c046e728>] (drm_gem_prime_import_dev) from [<c046e5bc>] (drm_gem_prime_fd_to_handle+0x84/0x17c)
> [<c046e5bc>] (drm_gem_prime_fd_to_handle) from [<c046edd0>] (drm_prime_fd_to_handle_ioctl+0x38/0x4c)
> [<c046edd0>] (drm_prime_fd_to_handle_ioctl) from [<c0460efc>] (drm_ioctl_kernel+0x90/0xc8)
> [<c0460efc>] (drm_ioctl_kernel) from [<c0461114>] (drm_ioctl+0x1e0/0x3b0)
> [<c0461114>] (drm_ioctl) from [<c01cae20>] (do_vfs_ioctl+0x90/0xa48)
> [<c01cae20>] (do_vfs_ioctl) from [<c01cb80c>] (ksys_ioctl+0x34/0x60)
> [<c01cb80c>] (ksys_ioctl) from [<c0009000>] (ret_fast_syscall+0x0/0x28)
> Exception stack(0xd81a9fa8 to 0xd81a9ff0)
> 9fa0:                   b6c69c88 bec613f8 00000009 c00c642e bec613f8 b86c4600
> 9fc0: b6c69c88 bec613f8 c00c642e 00000036 012762e0 01276348 00000300 012d91f8
> 9fe0: b6989f18 bec613dc b697185c b667be5c
> irq event stamp: 47905
> hardirqs last  enabled at (47913): [<c0098824>] console_unlock+0x46c/0x680
> hardirqs last disabled at (47922): [<c0098470>] console_unlock+0xb8/0x680
> softirqs last  enabled at (47754): [<c000a484>] __do_softirq+0x344/0x540
> softirqs last disabled at (47701): [<c0038700>] irq_exit+0x124/0x144
> ---[ end trace af477747acbcc642 ]---
> 
> The reason is the contiguous buffer exceeds the default maximum segment
> size of 64K as specified by dma_get_max_seg_size() in
> linux/dma-mapping.h.  Fix this by providing our own segment size, which
> is set to 2GiB to cover the window found in MMUv1 GPUs.
> 
> Signed-off-by: Russell King <rmk+kernel at armlinux.org.uk>

Fixes: 78c47830a5cb ("dma-debug: check scatterlist segments")

not really that there's a problem with that commit, but it is where the
warning was introduced.

> ---
> Patch against v4.20.
> 
>  drivers/gpu/drm/etnaviv/etnaviv_drv.c | 4 ++++
>  drivers/gpu/drm/etnaviv/etnaviv_drv.h | 1 +
>  2 files changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_drv.c b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> index 4713885012ab..e414f284f424 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> @@ -527,6 +527,9 @@ static int etnaviv_bind(struct device *dev)
>  	}
>  	drm->dev_private = priv;
>  
> +	dev->dma_parms = &priv->dma_parms;
> +	dma_set_max_seg_size(dev, SZ_2G);
> +
>  	mutex_init(&priv->gem_lock);
>  	INIT_LIST_HEAD(&priv->gem_list);
>  	priv->num_gpus = 0;
> @@ -564,6 +567,7 @@ static void etnaviv_unbind(struct device *dev)
>  
>  	component_unbind_all(dev, drm);
>  
> +	dev->dma_parms = NULL;
>  	drm->dev_private = NULL;
>  	kfree(priv);
>  
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_drv.h b/drivers/gpu/drm/etnaviv/etnaviv_drv.h
> index 8d02d1b7dcf5..b2930d1fe97c 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_drv.h
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_drv.h
> @@ -43,6 +43,7 @@ struct etnaviv_file_private {
>  
>  struct etnaviv_drm_private {
>  	int num_gpus;
> +	struct device_dma_parameters dma_parms;
>  	struct etnaviv_gpu *gpu[ETNA_MAX_PIPES];
>  
>  	/* list of GEM objects: */
> -- 
> 2.7.4
> 
> 

-- 
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