<html> <head> <meta content="text/html; charset=windows-1252" http-equiv="Content-Type"> </head> <body bgcolor="#FFFFFF" text="#000000"> <div class="moz-cite-prefix"> <blockquote type="cite"> The only downside to taking the locks all the time is for 99% of debug reads it's unnecessary and in theory could lead to performance/behaviour problems. </blockquote> Yeah, but performance isn't critical here and taking two locks compared to the rest of what we (IOCTL etc...) do is completely negligibly. <blockquote type="cite"> I've been using this on read for a while now and haven't noticed a problem. </blockquote> My concern is rather that somebody tries to write to the PM regs on accident or purpose without taking the lock. See, the kernel is usually responsible to keep people from doing stupid things with the hardware, even if those people are root and could do stupid things anyway. Well, you know what I mean? Regards, Christian. Am 10.10.2016 um 22:21 schrieb StDenis, Tom: </div> <blockquote cite="mid:CY4PR12MB1768813E554E6DB1A40F5848F7DB0@CY4PR12MB1768.namprd12.prod.outlook.com" type="cite"> <meta http-equiv="Content-Type" content="text/html; charset=windows-1252"> <style type="text/css" style="display:none;"></style> <div id="divtagdefaultwrapper" style="font-size:12pt;color:#000000;font-family:Calibri,Arial,Helvetica,sans-serif;"> The only downside to taking the locks all the time is for 99% of debug reads it's unnecessary and in theory could lead to performance/behaviour problems. I've been using this on read for a while now and haven't noticed a problem. Tom <div style="color: rgb(0, 0, 0);"> <hr tabindex="-1" style="display:inline-block; width:98%"> <div id="divRplyFwdMsg" dir="ltr">From: Christian König <a class="moz-txt-link-rfc2396E" href="mailto:deathsimple@vodafone.de"><deathsimple@vodafone.de></a> Sent: Monday, October 10, 2016 09:49 To: Tom St Denis; <a class="moz-txt-link-abbreviated" href="mailto:amd-gfx@lists.freedesktop.org">amd-gfx@lists.freedesktop.org</a> Cc: StDenis, Tom Subject: Re: [PATCH] drm/amd/amdgpu: Make debugfs write compliment read <div> </div> </div> <div> <div class="moz-cite-prefix">Would it hurt us to always take the looks (both the pm as well as grbm idx lock)? I don't think that would be much of an issue and I would have a better feeling with that. Christian. Am 10.10.2016 um 15:38 schrieb Tom St Denis: </div> <blockquote type="cite"> that's kind of the point. Its for debugging only. Also reads can already lock <div class="gmail_quote"> <div dir="ltr">On Mon, Oct 10, 2016, 09:25 Christian König <<a moz-do-not-send="true" href="mailto:deathsimple@vodafone.de">deathsimple@vodafone.de</a>> wrote: </div> <blockquote class="gmail_quote" style="margin:0 0 0 .8ex; border-left:1px #ccc solid; padding-left:1ex"> Mhm, that userspace controls if the lock is taken or not is a bit problematic, on the other hand only root could access that. Christian. Am 10.10.2016 um 14:51 schrieb Tom St Denis: > Add PG lock support as well as bank selection to > the MMIO write function. > > Signed-off-by: Tom St Denis <<a moz-do-not-send="true" href="mailto:tom.stdenis@amd.com" class="gmail_msg" target="_blank">tom.stdenis@amd.com</a>> > --- > drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 43 ++++++++++++++++++++++++++++++ > 1 file changed, 43 insertions(+) > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c > index 04c4aee70452..a9d83c1d7a43 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c > @@ -2637,10 +2637,45 @@ static ssize_t amdgpu_debugfs_regs_write(struct file *f, const char __user *buf, > struct amdgpu_device *adev = f->f_inode->i_private; > ssize_t result = 0; > int r; > + bool pm_pg_lock, use_bank; > + unsigned instance_bank, sh_bank, se_bank; > > if (size & 0x3 || *pos & 0x3) > return -EINVAL; > > + /* are we reading registers for which a PG lock is necessary? */ > + pm_pg_lock = (*pos >> 23) & 1; > + > + if (*pos & (1ULL << 62)) { > + se_bank = (*pos >> 24) & 0x3FF; > + sh_bank = (*pos >> 34) & 0x3FF; > + instance_bank = (*pos >> 44) & 0x3FF; > + > + if (se_bank == 0x3FF) > + se_bank = 0xFFFFFFFF; > + if (sh_bank == 0x3FF) > + sh_bank = 0xFFFFFFFF; > + if (instance_bank == 0x3FF) > + instance_bank = 0xFFFFFFFF; > + use_bank = 1; > + } else { > + use_bank = 0; > + } > + > + *pos &= 0x3FFFF; > + > + if (use_bank) { > + if ((sh_bank != 0xFFFFFFFF && sh_bank >= adev->gfx.config.max_sh_per_se) || > + (se_bank != 0xFFFFFFFF && se_bank >= adev->gfx.config.max_shader_engines)) > + return -EINVAL; > + mutex_lock(&adev->grbm_idx_mutex); > + amdgpu_gfx_select_se_sh(adev, se_bank, > + sh_bank, instance_bank); > + } > + > + if (pm_pg_lock) > + mutex_lock(&adev->pm.mutex); > + > while (size) { > uint32_t value; > > @@ -2659,6 +2694,14 @@ static ssize_t amdgpu_debugfs_regs_write(struct file *f, const char __user *buf, > size -= 4; > } > > + if (use_bank) { > + amdgpu_gfx_select_se_sh(adev, 0xffffffff, 0xffffffff, 0xffffffff); > + mutex_unlock(&adev->grbm_idx_mutex); > + } > + > + if (pm_pg_lock) > + mutex_unlock(&adev->pm.mutex); > + > return result; > } > </blockquote> </div> </blockquote> </div> </div> </div> </blockquote> </body> </html>