Message-ID: <20150106135551.GI31830@ulmo.nvidia.com>
Date:	Tue, 6 Jan 2015 14:55:52 +0100
From:	Thierry Reding <thierry.reding@...il.com>
To:	Vince Hsu <vinceh@...dia.com>
Cc:	Lucas Stach <dev@...xeye.de>, swarren@...dotorg.org,
	gnurou@...il.com, bskeggs@...hat.com, martin.peres@...e.fr,
	seven@...rod-online.com, samuel.pitoiset@...il.com,
	nouveau@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH nouveau 06/11] platform: complete the power up/down
 sequence

On Tue, Jan 06, 2015 at 08:13:01PM +0800, Vince Hsu wrote:
> 
> On 01/06/2015 07:36 PM, Thierry Reding wrote:
> >* PGP Signed by an unknown key
> >
> >On Tue, Jan 06, 2015 at 05:34:01PM +0800, Vince Hsu wrote:
> >>On 01/05/2015 11:25 PM, Thierry Reding wrote:
> >>>>Old Signed by an unknown key
> >>>On Thu, Dec 25, 2014 at 10:42:58AM +0800, Vince Hsu wrote:
> >>>>On 12/24/2014 09:23 PM, Lucas Stach wrote:
> >>>>>Am Dienstag, den 23.12.2014, 18:39 +0800 schrieb Vince Hsu:
> >>>>>>This patch adds some missing pieces of the rail gaing/ungating sequence that
> >>>>>>can improve the stability in theory.
> >>>>>>
> >>>>>>Signed-off-by: Vince Hsu <vinceh@...dia.com>
> >>>>>>---
> >>>>>>  drm/nouveau_platform.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> >>>>>>  drm/nouveau_platform.h |  3 +++
> >>>>>>  2 files changed, 45 insertions(+)
> >>>>>>
> >>>>>>diff --git a/drm/nouveau_platform.c b/drm/nouveau_platform.c
> >>>>>>index 68788b17a45c..527fe2358fc9 100644
> >>>>>>--- a/drm/nouveau_platform.c
> >>>>>>+++ b/drm/nouveau_platform.c
> >>>>>>@@ -25,9 +25,11 @@
> >>>>>>  #include <linux/module.h>
> >>>>>>  #include <linux/platform_device.h>
> >>>>>>  #include <linux/of.h>
> >>>>>>+#include <linux/of_platform.h>
> >>>>>>  #include <linux/reset.h>
> >>>>>>  #include <linux/regulator/consumer.h>
> >>>>>>  #include <soc/tegra/fuse.h>
> >>>>>>+#include <soc/tegra/mc.h>
> >>>>>>  #include <soc/tegra/pmc.h>
> >>>>>>  #include "nouveau_drm.h"
> >>>>>>@@ -61,6 +63,9 @@ static int nouveau_platform_power_up(struct nouveau_platform_gpu *gpu)
> >>>>>>  	reset_control_deassert(gpu->rst);
> >>>>>>  	udelay(10);
> >>>>>>+	tegra_mc_flush(gpu->mc, gpu->swgroup, false);
> >>>>>>+	udelay(10);
> >>>>>>+
> >>>>>>  	return 0;
> >>>>>>  err_clamp:
> >>>>>>@@ -77,6 +82,14 @@ static int nouveau_platform_power_down(struct nouveau_platform_gpu *gpu)
> >>>>>>  {
> >>>>>>  	int err;
> >>>>>>+	tegra_mc_flush(gpu->mc, gpu->swgroup, true);
> >>>>>>+	udelay(10);
> >>>>>>+
> >>>>>>+	err = tegra_powergate_gpu_set_clamping(true);
> >>>>>>+	if (err)
> >>>>>>+		return err;
> >>>>>>+	udelay(10);
> >>>>>>+
> >>>>>>  	reset_control_assert(gpu->rst);
> >>>>>>  	udelay(10);
> >>>>>>@@ -91,6 +104,31 @@ static int nouveau_platform_power_down(struct nouveau_platform_gpu *gpu)
> >>>>>>  	return 0;
> >>>>>>  }
> >>>>>>+static int nouveau_platform_get_mc(struct device *dev,
> >>>>>>+		struct tegra_mc **mc, unsigned int *swgroup)
> >>>>>Uhm, no. If this is needed this has to be a Tegra MC function and not
> >>>>>burried into nouveau code. You are using knowledge about the internal
> >>>>>workings of the MC driver here.
> >>>>>
> >>>>>Also this should probably only take the Dt node pointer as argument and
> >>>>>return a something like a tegra_mc_client struct that contains both the
> >>>>>MC device pointer and the swgroup so you can pass that to
> >>>>>tegra_mc_flush().
> >>>>Good idea. I will have something as below in V2 if there is no other
> >>>>comments for this.
> >>>>
> >>>>tegra_mc_client *tegra_mc_find_client(struct device_node *node)
> >>>>{
> >>>>     ...
> >>>>     ret = of_parse_phandle_with_args(node, "nvidia,memory-client", ...)
> >>>>     ...
> >>>>}
> >>>>
> >>>>There were some discussion about this few weeks ago. I'm not sure whether we
> >>>>have some conclusion/implementation though. Thierry?
> >>>>
> >>>>http://lists.infradead.org/pipermail/linux-arm-kernel/2014-December/308703.html
> >>>I don't think client is a good fit here. Flushing is done per SWGROUP
> >>>(on all clients of the SWGROUP). So I think we'll want something like:
> >>>
> >>>	gpu@0,57000000 {
> >>>		...
> >>>		nvidia,swgroup = <&mc TEGRA_SWGROUP_GPU>;
> >>>		...
> >>>	};
> >>>
> >>>In the DT and return a struct tegra_mc_swgroup along the lines of:
> >>>
> >>>	struct tegra_mc_client {
> >>>		unsigned int id;
> >>>		unsigned int swgroup;
> >>>
> >>>		struct list_head list;
> >>>	};
> >>>
> >>>	struct tegra_mc_swgroup {
> >>>		struct list_head clients;
> >>>		unsigned int id;
> >>>	};
> >>>
> >>>Where tegra_mc_swgroup.clients is a list of struct tegra_mc_client
> >>>structures, each representing a memory client pertaining to the
> >>>SWGROUP.
> >>Based on your suggestion above, I created a struct tegra_mc_swgroup:
> >>
> >>struct tegra_mc_swgroup {
> >>     unsigned int id;
> >>     struct tegra_mc *mc;
> >>     struct list_head head;
> >>     struct list_head clients;
> >>};
> >>
> >>And added the list head in the struct tegra_mc_soc.
> >>
> >>struct tegra_mc_soc {
> >>     struct tegra_mc_client *clients;
> >>     unsigned int num_clients;
> >>
> >>     struct tegra_mc_hr *hr_clients;
> >>     unsigned int num_hr_clients;
> >Why do you still need these?
> This part is added in "[PATCH 2/11] memory: tegra: add mc flush support" and
> "[PATCH 3/11] memory: tegra: add flush operation for Tegra124 memory
> clients"
> for the hotreset registers.

Right. Perhaps calling this structure tegra_mc_hotreset and the
variables *_hotresets would be a good idea to clarify that they aren't
actually per-client but per-SWGROUP.

> >>Created one function to build the swgroup list.
> >>
> >>static int tegra_mc_build_swgroup(struct tegra_mc *mc)
> >>{
> >>     int i;
> >>
> >>     for (i = 0; i < mc->soc->num_clients; i++) {
> >>         struct tegra_mc_swgroup *sg;
> >>         bool found = false;
> >>
> >>         list_for_each_entry(sg, &mc->soc->swgroups, head) {
> >>             if (sg->id == mc->soc->clients[i].swgroup) {
> >>                 found = true;
> >>                 break;
> >>             }
> >>         }
> >Can't you use your new tegra_mc_find_swgroup() function here? That way
> >you could turn it into something slightly more readable:
> The tegra_mc_build_swgroup() is called during driver probe, and after that
> the swgroup list is established and then the tegra_mc_find_swgroup() can
> work.

But you can reuse tegra_mc_find_swgroup() instead of open-coding it to
search the partial list. The code will be exactly the same, won't it?

> >	unsigned int swgroup = mc->soc->clients[i].swgroup;
> >	struct tegra_mc_swgroup *group;
> >
> >	group = tegra_mc_find_swgroup(mc, swgroup);
> The tegra_mc_find_swgroup() is expected to be called outside the mc driver
> and
> can only take the device node as argument because other drivers do not have
> the mc instance information unless they call tegra_mc_find_swgroup() or
> tegra_mc_find_client().

You can do that by making a low-level function that works on the struct
tegra_mc * and an unsigned int swgroup which is only used internally and
then wrap a public function around it that deals with looking up the
struct tegra_mc * and SWGROUP ID.

Thierry

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