Re: [PATCH nouveau 06/11] platform: complete the power up/down sequence

[Thierry Reding]

On Tue, Jan 06, 2015 at 05:34:01PM +0800, Vince Hsu wrote:
> 
> On 01/05/2015 11:25 PM, Thierry Reding wrote:
> >* PGP 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@xxxxxxxxxx>
> >>>>---
> >>>>  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?

>     struct list_head swgroups;

This doesn't belong in struct tegra_mc_soc because that's meant to be
static information about the specific variant of the memory-controller.
Put it in struct tegra_mc instead.

> ...
> 
> 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:

	unsigned int swgroup = mc->soc->clients[i].swgroup;
	struct tegra_mc_swgroup *group;

	group = tegra_mc_find_swgroup(mc, swgroup);
	if (!group) {
		/* allocates and adds to mc->swgroups */
		group = tegra_mc_add_swgroup(mc, swgroup);
		if (!group)
			return -ENOMEM;
	}

	list_add_tail(&group->list, &mc->swgroups);

where tegra_mc_add_swgroup() is something like this:

	group = devm_kzalloc(mc->dev, sizeof(*group), GFP_KERNEL);
	if (!group)
		return NULL;

	INIT_LIST_HEAD(&group->clients);
	group->mc = mc;
	group->id = id;

I don't like very much how this duplicates information that is already
available in tegra_mc_soc, but I can't think of a better way to couple
the SWGROUP ID with the struct tegra_mc *, so I think we'll have to
proceed with something like the above.

Thierry

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