On Tue, Jan 21, 2020 at 11:19 AM Douglas Anderson <dianders@xxxxxxxxxxxx> wrote: > > From: Sean Paul <seanpaul@xxxxxxxxxxxx> > > Turning on CONFIG_DMA_API_DEBUG_SG results in the following error: > > [ 12.078665] msm ae00000.mdss: DMA-API: mapping sg segment longer than device claims to support [len=3526656] [max=65536] > [ 12.089870] WARNING: CPU: 6 PID: 334 at /mnt/host/source/src/third_party/kernel/v4.19/kernel/dma/debug.c:1301 debug_dma_map_sg+0x1dc/0x318 > [ 12.102655] Modules linked in: joydev > [ 12.106442] CPU: 6 PID: 334 Comm: frecon Not tainted 4.19.0 #2 > [ 12.112450] Hardware name: Google Cheza (rev3+) (DT) > [ 12.117566] pstate: 60400009 (nZCv daif +PAN -UAO) > [ 12.122506] pc : debug_dma_map_sg+0x1dc/0x318 > [ 12.126995] lr : debug_dma_map_sg+0x1dc/0x318 > [ 12.131487] sp : ffffff800cc3ba80 > [ 12.134913] x29: ffffff800cc3ba80 x28: 0000000000000000 > [ 12.140395] x27: 0000000000000004 x26: 0000000000000004 > [ 12.145868] x25: ffffff8008e55b18 x24: 0000000000000000 > [ 12.151337] x23: 00000000ffffffff x22: ffffff800921c000 > [ 12.156809] x21: ffffffc0fa75b080 x20: ffffffc0f7195090 > [ 12.162280] x19: ffffffc0f1c53280 x18: 0000000000000000 > [ 12.167749] x17: 0000000000000000 x16: 0000000000000000 > [ 12.173218] x15: 0000000000000000 x14: 0720072007200720 > [ 12.178689] x13: 0720072007200720 x12: 0720072007200720 > [ 12.184161] x11: 0720072007200720 x10: 0720072007200720 > [ 12.189641] x9 : ffffffc0f1fc6b60 x8 : 0000000000000000 > [ 12.195110] x7 : ffffff8008132ce0 x6 : 0000000000000000 > [ 12.200585] x5 : 0000000000000000 x4 : ffffff8008134734 > [ 12.206058] x3 : ffffff800cc3b830 x2 : ffffffc0f1fc6240 > [ 12.211532] x1 : 25045a74f48a7400 x0 : 25045a74f48a7400 > [ 12.217006] Call trace: > [ 12.219535] debug_dma_map_sg+0x1dc/0x318 > [ 12.223671] get_pages+0x19c/0x20c > [ 12.227177] msm_gem_fault+0x64/0xfc > [ 12.230874] __do_fault+0x3c/0x140 > [ 12.234383] __handle_mm_fault+0x70c/0xdb8 > [ 12.238603] handle_mm_fault+0xac/0xc4 > [ 12.242473] do_page_fault+0x1bc/0x3d4 > [ 12.246342] do_translation_fault+0x54/0x88 > [ 12.250652] do_mem_abort+0x60/0xf0 > [ 12.254250] el0_da+0x20/0x24 > [ 12.257317] irq event stamp: 67260 > [ 12.260828] hardirqs last enabled at (67259): [<ffffff8008132d0c>] console_unlock+0x214/0x608 > [ 12.269693] hardirqs last disabled at (67260): [<ffffff8008080e0c>] do_debug_exception+0x5c/0x178 > [ 12.278820] softirqs last enabled at (67256): [<ffffff8008081664>] __do_softirq+0x4d4/0x520 > [ 12.287510] softirqs last disabled at (67249): [<ffffff80080be574>] irq_exit+0xa8/0x100 > [ 12.295742] ---[ end trace e63cfc40c313ffab ]--- > > The root of the problem is that the default segment size for sgt is > (UINT_MAX & PAGE_MASK), and the default segment size for device dma is > 64K. As such, if you compare the 2, you would deduce that the sg segment > will overflow the device's capacity. In reality, the hardware can > accommodate the larger sg segments, it's just not initializing its max > segment properly. This patch initializes the max segment size for the > mdss device, which gets rid of that pesky warning. > > Reported-by: Stephen Boyd <swboyd@xxxxxxxxxxxx> > Signed-off-by: Sean Paul <seanpaul@xxxxxxxxxxxx> > Tested-by: Stephen Boyd <swboyd@xxxxxxxxxxxx> > Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx> > --- > This patch has been floating in the ether for over a year [1]. I know > next to nothing about it, but I'm told it's still useful so I'm > helpfully reposting it. Please enjoy. This looks like the right thing to do.. sorry I overlooked the patch first time around Reviewed-by: Rob Clark <robdclark@xxxxxxxxx> (since I've already sent PR for msm-next, could we pick this up via drm-misc?) BR, -R > > [1] https://lore.kernel.org/r/20181106213239.52133-1-sean@xxxxxxxxxx > > drivers/gpu/drm/msm/msm_drv.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c > index c26219c7a49f..e4b750b0c2d3 100644 > --- a/drivers/gpu/drm/msm/msm_drv.c > +++ b/drivers/gpu/drm/msm/msm_drv.c > @@ -441,6 +441,14 @@ static int msm_drm_init(struct device *dev, struct drm_driver *drv) > if (ret) > goto err_msm_uninit; > > + if (!dev->dma_parms) { > + dev->dma_parms = devm_kzalloc(dev, sizeof(*dev->dma_parms), > + GFP_KERNEL); > + if (!dev->dma_parms) > + return -ENOMEM; > + } > + dma_set_max_seg_size(dev, DMA_BIT_MASK(32)); > + > msm_gem_shrinker_init(ddev); > > switch (get_mdp_ver(pdev)) { > -- > 2.25.0.341.g760bfbb309-goog >
