| Message ID | 20170130164921.20744-2-robdclark@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Rob Clark <robdclark@gmail.com> writes: > The plan is to use the OPP bindings. For now, remove the documentation > for qcom,gpu-pwrlevels, and make the driver fall back to a safe low > clock if the node is not present. > > Note that no upstream dtb use this node. For now we keep compatibility > with this node to avoid breaking compatibility with downstream android > dt files. > > Signed-off-by: Rob Clark <robdclark@gmail.com> Will we need the bus frequency knobs that I see in the old pwrlevels node? If so, what would the plan be for doing that within OPP?
On Mon, Jan 30, 2017 at 1:21 PM, Eric Anholt <eric@anholt.net> wrote: > Rob Clark <robdclark@gmail.com> writes: > >> The plan is to use the OPP bindings. For now, remove the documentation >> for qcom,gpu-pwrlevels, and make the driver fall back to a safe low >> clock if the node is not present. >> >> Note that no upstream dtb use this node. For now we keep compatibility >> with this node to avoid breaking compatibility with downstream android >> dt files. >> >> Signed-off-by: Rob Clark <robdclark@gmail.com> > > Will we need the bus frequency knobs that I see in the old pwrlevels > node? If so, what would the plan be for doing that within OPP? So, that I think is one of the open questions. Jordan knows this stuff a lot better than I, but my understanding is that bus and clk scale *basically* independently, except that a given gpu clk we want a different minimum bus clk. (I'm not sure if that is a functional requirement, or just what qcom arrived at after performance tuning..) There is some work ongoing to get some sort of upstream bus scaling scaling, although I'm not really sure yet what the bindings for this would look like. So basically short answer is "I don't know.. there are too many open questions". Maybe in the end we re-introduce qcom,gpu-pwrlevels. But I think for now the approach of not documenting it and have safe/slow clk fallback in the driver is a reasonable way to move forward with getting some basic gpu nodes into upstream dts files. BR, -R
Rob Clark <robdclark@gmail.com> writes: > On Mon, Jan 30, 2017 at 1:21 PM, Eric Anholt <eric@anholt.net> wrote: >> Rob Clark <robdclark@gmail.com> writes: >> >>> The plan is to use the OPP bindings. For now, remove the documentation >>> for qcom,gpu-pwrlevels, and make the driver fall back to a safe low >>> clock if the node is not present. >>> >>> Note that no upstream dtb use this node. For now we keep compatibility >>> with this node to avoid breaking compatibility with downstream android >>> dt files. >>> >>> Signed-off-by: Rob Clark <robdclark@gmail.com> >> >> Will we need the bus frequency knobs that I see in the old pwrlevels >> node? If so, what would the plan be for doing that within OPP? > > So, that I think is one of the open questions. Jordan knows this > stuff a lot better than I, but my understanding is that bus and clk > scale *basically* independently, except that a given gpu clk we want a > different minimum bus clk. > > (I'm not sure if that is a functional requirement, or just what qcom > arrived at after performance tuning..) > > There is some work ongoing to get some sort of upstream bus scaling > scaling, although I'm not really sure yet what the bindings for this > would look like. > > So basically short answer is "I don't know.. there are too many open > questions". Maybe in the end we re-introduce qcom,gpu-pwrlevels. But > I think for now the approach of not documenting it and have safe/slow > clk fallback in the driver is a reasonable way to move forward with > getting some basic gpu nodes into upstream dts files. Yeah, letting the upstream DT bind without the custom OPP stuff for now seems like progress. If we find that the safe fast freq is too high then we can drop it down later, and that would just put more pressure on getting the OPP work finished. Reviewed-by: Eric Anholt <eric@anholt.net>
On Mon, Jan 30, 2017 at 11:49:18AM -0500, Rob Clark wrote: > The plan is to use the OPP bindings. For now, remove the documentation > for qcom,gpu-pwrlevels, and make the driver fall back to a safe low > clock if the node is not present. > > Note that no upstream dtb use this node. For now we keep compatibility > with this node to avoid breaking compatibility with downstream android > dt files. > > Signed-off-by: Rob Clark <robdclark@gmail.com> > --- > Documentation/devicetree/bindings/display/msm/gpu.txt | 15 --------------- > drivers/gpu/drm/msm/adreno/adreno_device.c | 6 ++++-- > 2 files changed, 4 insertions(+), 17 deletions(-) Acked-by: Rob Herring <robh@kernel.org>
On Mon, Jan 30, 2017 at 01:35:47PM -0500, Rob Clark wrote: > On Mon, Jan 30, 2017 at 1:21 PM, Eric Anholt <eric@anholt.net> wrote: > > Rob Clark <robdclark@gmail.com> writes: > > > >> The plan is to use the OPP bindings. For now, remove the documentation > >> for qcom,gpu-pwrlevels, and make the driver fall back to a safe low > >> clock if the node is not present. > >> > >> Note that no upstream dtb use this node. For now we keep compatibility > >> with this node to avoid breaking compatibility with downstream android > >> dt files. > >> > >> Signed-off-by: Rob Clark <robdclark@gmail.com> > > > > Will we need the bus frequency knobs that I see in the old pwrlevels > > node? If so, what would the plan be for doing that within OPP? > > So, that I think is one of the open questions. Jordan knows this > stuff a lot better than I, but my understanding is that bus and clk > scale *basically* independently, except that a given gpu clk we want a > different minimum bus clk. > > (I'm not sure if that is a functional requirement, or just what qcom > arrived at after performance tuning..) > > There is some work ongoing to get some sort of upstream bus scaling > scaling, although I'm not really sure yet what the bindings for this > would look like. > > So basically short answer is "I don't know.. there are too many open > questions". Maybe in the end we re-introduce qcom,gpu-pwrlevels. But > I think for now the approach of not documenting it and have safe/slow > clk fallback in the driver is a reasonable way to move forward with > getting some basic gpu nodes into upstream dts files. Rob has it right. On a fully optimized platform the bus does scale independently from the GPU but when we switch GPU levels up we need to immediately kick the bus to a new baseline level otherwise it underruns. Eventually somebody will have to figure out how to make OPP work with both device and bus frequency. Perhaps that will happen by the time useful bus scaling hits the kernel, otherwise we will have to suffer along with two tables and a closer relationship between the GPU driver and the devfreq governor than any of us are comfortable with. Luckily for this discussion that someday is in the future and we can focus on doing the frqeuency right. Jordan
diff --git a/Documentation/devicetree/bindings/display/msm/gpu.txt b/Documentation/devicetree/bindings/display/msm/gpu.txt index 67d0a58..747b984 100644 --- a/Documentation/devicetree/bindings/display/msm/gpu.txt +++ b/Documentation/devicetree/bindings/display/msm/gpu.txt @@ -12,12 +12,6 @@ Required properties: * "mem_iface_clk" - qcom,chipid: gpu chip-id. Note this may become optional for future devices if we can reliably read the chipid from hw -- qcom,gpu-pwrlevels: list of operating points - - compatible: "qcom,gpu-pwrlevels" - - for each qcom,gpu-pwrlevel: - - qcom,gpu-freq: requested gpu clock speed - - NOTE: downstream android driver defines additional parameters to - configure memory bandwidth scaling per OPP. Example: @@ -39,14 +33,5 @@ Example: <&mmcc GFX3D_AHB_CLK>, <&mmcc MMSS_IMEM_AHB_CLK>; qcom,chipid = <0x03020100>; - qcom,gpu-pwrlevels { - compatible = "qcom,gpu-pwrlevels"; - qcom,gpu-pwrlevel@0 { - qcom,gpu-freq = <450000000>; - }; - qcom,gpu-pwrlevel@1 { - qcom,gpu-freq = <27000000>; - }; - }; }; }; diff --git a/drivers/gpu/drm/msm/adreno/adreno_device.c b/drivers/gpu/drm/msm/adreno/adreno_device.c index e130b5e..7b9181b2 100644 --- a/drivers/gpu/drm/msm/adreno/adreno_device.c +++ b/drivers/gpu/drm/msm/adreno/adreno_device.c @@ -224,8 +224,10 @@ static int adreno_bind(struct device *dev, struct device *master, void *data) } if (!config.fast_rate) { - dev_err(dev, "could not find clk rates\n"); - return -ENXIO; + dev_warn(dev, "could not find clk rates\n"); + /* This is a safe low speed for all devices: */ + config.fast_rate = 200000000; + config.slow_rate = 27000000; } for (i = 0; i < ARRAY_SIZE(quirks); i++)
The plan is to use the OPP bindings. For now, remove the documentation for qcom,gpu-pwrlevels, and make the driver fall back to a safe low clock if the node is not present. Note that no upstream dtb use this node. For now we keep compatibility with this node to avoid breaking compatibility with downstream android dt files. Signed-off-by: Rob Clark <robdclark@gmail.com> --- Documentation/devicetree/bindings/display/msm/gpu.txt | 15 --------------- drivers/gpu/drm/msm/adreno/adreno_device.c | 6 ++++-- 2 files changed, 4 insertions(+), 17 deletions(-)