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From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: Maxime Ripard <maxime@cerno.tech>,
	Stefan Wahren <stefan.wahren@i2se.com>
Cc: Eric Anholt <eric@anholt.net>,
	Tim Gover <tim.gover@raspberrypi.com>,
	Dave Stevenson <dave.stevenson@raspberrypi.com>,
	Stephen Boyd <sboyd@kernel.org>,
	Michael Turquette <mturquette@baylibre.com>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	linux-clk@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com,
	linux-rpi-kernel@lists.infradead.org,
	Phil Elwell <phil@raspberrypi.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 16/89] clk: bcm: rpi: Add clock id to data
Date: Tue, 25 Feb 2020 15:33:23 +0100	[thread overview]
Message-ID: <5754451af3663ba39e8358dd15e586ee1485f86a.camel@suse.de> (raw)
In-Reply-To: <20200225095433.tyxamibqyrgw5355@gilmour.lan>

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Hi Maxime,

On Tue, 2020-02-25 at 10:54 +0100, Maxime Ripard wrote:
> Hi Stefan,
> 
> On Mon, Feb 24, 2020 at 08:25:46PM +0100, Stefan Wahren wrote:
> > Hi Maxime,
> > 
> > Am 24.02.20 um 10:06 schrieb Maxime Ripard:
> > > The driver has really only supported one clock so far and has hardcoded
> > > the
> > > ID used in communications with the firmware in all the functions
> > > implementing the clock framework hooks. Let's store that in the clock data
> > > structure so that we can support more clocks later on.
> > 
> > thank you for this series. I looked through it but i couldn't find an
> > explanation why we need to expose firmware clocks via DT instead of
> > extending clk-bcm2835. The whole pllb / clk-raspberrypi stuff was an
> > exception to get cpufreq working. I prefer to keep it an exception.
> 
> Thanks for pointing this out, I indeed forgot to address it in my
> cover letter or my commit log.
> 
> I'm not quite sure what the situation was with the previous
> RaspberryPi, but the RPi4 firmware does a bunch of things under the
> hood to make sure that everything works as expected:
> 
>  - The HSM (and V3D) clocks will be reparented to multiple PLLs
>    depending on the rate being asked for.
>  - Still depending on the rate, the firmware will adjust the voltage
>    of the various PLLs.
>  - Depending on the temperature of the CPU and GPU, the firmware will
>    change the rate of clocks to throttle in case of the cores
>    overheating, with all the fallout that might happen to clocks
>    deriving from it.
>  - No matter what we choose to do in Linux, this will happen so
>    whether or not we want to do it, so doing it behind the firmware's
>    back (or the firmware doing it behind Linux's back) will only
>    result in troubles, with voltages too low, or the firmware trying
>    to access the same register at the same time than the Linux driver
>    would, etc.
> 
> So all in all, it just seems much easier and safer to use the firmware
> clocks.

I agree with your assesment. Both DVFS and overheating/overvoltage protections
will cause trouble, if not, make a Linux solution impossible while using the
Foundation's firmware.

Please note that, as Stefan says, it'd be nice to keep track of those arguments
somewhere in the commit messages.

Regards,
Nicolas


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  reply	other threads:[~2020-02-25 14:33 UTC|newest]

Thread overview: 161+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-24  9:06 [PATCH 00/89] drm/vc4: Support BCM2711 Display Pipeline Maxime Ripard
2020-02-24  9:06 ` [PATCH 01/89] dt-bindings: i2c: brcmstb: Convert the BRCMSTB binding to a schema Maxime Ripard
2020-02-24 17:40   ` Florian Fainelli
2020-02-25 18:14   ` Rob Herring
2020-03-10 10:07   ` Wolfram Sang
2020-03-10 10:07   ` Wolfram Sang
2020-02-24  9:06 ` [PATCH 02/89] dt-bindings: i2c: brcmstb: Add BCM2711 BSC/AUTO-I2C binding Maxime Ripard
2020-02-24 17:48   ` Florian Fainelli
2020-02-25 18:15   ` Rob Herring
2020-03-10 10:07   ` Wolfram Sang
2020-02-24  9:06 ` [PATCH 03/89] i2c: brcmstb: Support BCM2711 HDMI BSC controllers Maxime Ripard
2020-02-24 17:44   ` Florian Fainelli
2020-03-10 10:12   ` Wolfram Sang
2020-02-24  9:06 ` [PATCH 04/89] i2c: brcmstb: Allow to compile it on BCM2835 Maxime Ripard
2020-02-24 17:39   ` Florian Fainelli
2020-03-10 10:16   ` Wolfram Sang
2020-02-24  9:06 ` [PATCH 05/89] clk: Return error code when of provider pointer is NULL Maxime Ripard
2020-03-12 23:13   ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 06/89] dt-bindings: clock: Add a binding for the RPi Firmware clocks Maxime Ripard
2020-02-25 18:16   ` Rob Herring
2020-03-12 23:14     ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 07/89] clk: bcm: rpi: Allow the driver to be probed by DT Maxime Ripard
2020-02-25 16:00   ` Nicolas Saenz Julienne
2020-02-26 15:01     ` Maxime Ripard
2020-02-28 19:57       ` Nicolas Saenz Julienne
2020-03-01 12:16   ` Stefan Wahren
2020-03-23 15:13     ` Maxime Ripard
2020-02-24  9:06 ` [PATCH 08/89] clk: bcm: rpi: Statically init clk_init_data Maxime Ripard
2020-02-25 16:05   ` Nicolas Saenz Julienne
2020-02-24  9:06 ` [PATCH 09/89] clk: bcm: rpi: Use clk_hw_register for pllb_arm Maxime Ripard
2020-02-25 16:11   ` Nicolas Saenz Julienne
2020-03-12 23:17   ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 10/89] clk: bcm: rpi: Remove global pllb_arm clock pointer Maxime Ripard
2020-02-25 16:13   ` Nicolas Saenz Julienne
2020-02-26 14:26     ` Maxime Ripard
2020-02-26 14:57       ` Nicolas Saenz Julienne
2020-02-24  9:06 ` [PATCH 11/89] clk: bcm: rpi: Make sure pllb_arm is removed Maxime Ripard
2020-02-25 16:14   ` Nicolas Saenz Julienne
2020-03-12 23:20   ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 12/89] clk: bcm: rpi: Remove pllb_arm_lookup global pointer Maxime Ripard
2020-02-25 16:16   ` Nicolas Saenz Julienne
2020-03-12 23:21   ` Stephen Boyd
2020-03-13  1:13   ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 13/89] clk: bcm: rpi: Switch to clk_hw_register_clkdev Maxime Ripard
2020-02-25 16:17   ` Nicolas Saenz Julienne
2020-03-13  1:12   ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 14/89] clk: bcm: rpi: Make sure the clkdev lookup is removed Maxime Ripard
2020-02-25 16:19   ` Nicolas Saenz Julienne
2020-03-13  1:11   ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 15/89] clk: bcm: rpi: Create a data structure for the clocks Maxime Ripard
2020-02-25 16:24   ` Nicolas Saenz Julienne
2020-03-13  1:11   ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 16/89] clk: bcm: rpi: Add clock id to data Maxime Ripard
2020-02-24 19:25   ` Stefan Wahren
2020-02-25  9:54     ` Maxime Ripard
2020-02-25 14:33       ` Nicolas Saenz Julienne [this message]
2020-02-25 16:24   ` Nicolas Saenz Julienne
2020-03-13  1:11   ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 17/89] clk: bcm: rpi: Pass the clocks data to the firmware function Maxime Ripard
2020-02-25 16:26   ` Nicolas Saenz Julienne
2020-03-13  1:09   ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 18/89] clk: bcm: rpi: Rename is_prepared function Maxime Ripard
2020-02-25 16:45   ` Nicolas Saenz Julienne
2020-03-13  1:09   ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 19/89] clk: bcm: rpi: Split pllb clock hooks Maxime Ripard
2020-03-13  1:08   ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 20/89] clk: bcm: rpi: Make the PLLB registration function return a clk_hw Maxime Ripard
2020-03-13  1:01   ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 21/89] clk: bcm: rpi: Add DT provider for the clocks Maxime Ripard
2020-03-13  1:01   ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 22/89] clk: bcm: rpi: Discover the firmware clocks Maxime Ripard
2020-02-24 16:47   ` kbuild test robot
2020-02-24 16:47   ` [PATCH] clk: bcm: rpi: fix noderef.cocci warnings kbuild test robot
2020-02-24 18:15   ` [PATCH 22/89] clk: bcm: rpi: Discover the firmware clocks Florian Fainelli
2020-02-26 14:15     ` Maxime Ripard
2020-02-24 20:24   ` kbuild test robot
2020-03-13  1:08   ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 23/89] ARM: dts: bcm2711: Add firmware clocks node Maxime Ripard
2020-02-24  9:06 ` [PATCH 24/89] reset: Move reset-simple header out of drivers/reset Maxime Ripard
2020-02-24  9:06 ` [PATCH 25/89] reset: simple: Add reset callback Maxime Ripard
2020-03-04 12:03   ` Philipp Zabel
2020-02-24  9:06 ` [PATCH 26/89] dt-bindings: clock: Add BCM2711 DVP binding Maxime Ripard
2020-02-25 18:17   ` Rob Herring
2020-02-24  9:06 ` [PATCH 27/89] clk: bcm: Add BCM2711 DVP driver Maxime Ripard
2020-03-13  1:00   ` Stephen Boyd
2020-03-23 10:56     ` Maxime Ripard
2020-03-25  2:20       ` Stephen Boyd
2020-02-24  9:06 ` [PATCH 28/89] ARM: dts: bcm2711: Add HDMI DVP Maxime Ripard
2020-02-24  9:06 ` [PATCH 29/89] dt-bindings: display: Convert VC4 bindings to schemas Maxime Ripard
2020-02-24 18:41   ` Rob Herring
2020-02-25 11:54     ` Maxime Ripard
2020-02-25 14:02       ` Rob Herring
2020-02-24  9:06 ` [PATCH 30/89] dt-bindings: display: vc4: dpi: Add missing clock-names property Maxime Ripard
2020-02-25 18:17   ` Rob Herring
2020-02-24  9:06 ` [PATCH 31/89] dt-bindings: display: vc4: dsi: Add missing clock properties Maxime Ripard
2020-02-25 18:18   ` Rob Herring
2020-02-24  9:06 ` [PATCH 32/89] dt-bindings: display: vc4: hdmi: Add missing clock-names property Maxime Ripard
2020-02-25 18:18   ` Rob Herring
2020-02-24  9:06 ` [PATCH 33/89] dt-bindings: display: vc4: Document BCM2711 VC5 Maxime Ripard
2020-02-25 18:18   ` Rob Herring
2020-02-24  9:06 ` [PATCH 34/89] drm/vc4: drv: Add include guards Maxime Ripard
2020-02-24  9:06 ` [PATCH 35/89] drm/vc4: drv: Support BCM2711 Maxime Ripard
2020-02-24  9:06 ` [PATCH 36/89] drm/vc4: drv: Add support for the BCM2711 HVS5 Maxime Ripard
2020-02-24  9:06 ` [PATCH 37/89] drm/vc4: plane: Improve LBM usage Maxime Ripard
2020-02-24  9:06 ` [PATCH 38/89] drm/vc4: plane: Move planes creation to its own function Maxime Ripard
2020-02-24  9:06 ` [PATCH 39/89] drm/vc4: plane: Move additional planes creation to driver Maxime Ripard
2020-02-24  9:06 ` [PATCH 40/89] drm/vc4: plane: Register all the planes at once Maxime Ripard
2020-02-24  9:06 ` [PATCH 41/89] drm/vc4: plane: Create overlays for any CRTC Maxime Ripard
2020-02-24  9:06 ` [PATCH 42/89] drm/vc4: plane: Create more planes Maxime Ripard
2020-02-24  9:06 ` [PATCH 43/89] drm/vc4: crtc: Rename SoC data structures Maxime Ripard
2020-02-24  9:06 ` [PATCH 44/89] drm/vc4: crtc: Move crtc state to common header Maxime Ripard
2020-02-24  9:06 ` [PATCH 45/89] drm/vc4: crtc: Deal with different number of pixel per clock Maxime Ripard
2020-02-24  9:06 ` [PATCH 46/89] drm/vc4: crtc: Use a shared interrupt Maxime Ripard
2020-02-24  9:06 ` [PATCH 47/89] drm/vc4: crtc: Turn static const variable into a define Maxime Ripard
2020-02-24  9:06 ` [PATCH 48/89] drm/vc4: crtc: Move the cob allocation outside of bind Maxime Ripard
2020-02-24  9:06 ` [PATCH 49/89] drm/vc4: crtc: Rename HVS channel to output Maxime Ripard
2020-02-24  9:06 ` [PATCH 50/89] drm/vc4: crtc: Use local chan variable Maxime Ripard
2020-02-24  9:06 ` [PATCH 51/89] drm/vc4: crtc: Enable and disable the PV in atomic_enable / disable Maxime Ripard
2020-02-24  9:06 ` [PATCH 52/89] drm/vc4: crtc: Assign output to channel automatically Maxime Ripard
2020-02-24  9:06 ` [PATCH 53/89] drm/vc4: crtc: Add FIFO depth to vc4_crtc_data Maxime Ripard
2020-02-24  9:06 ` [PATCH 54/89] drm/vc4: crtc: Add function to compute FIFO level bits Maxime Ripard
2020-02-24  9:06 ` [PATCH 55/89] drm/vc4: crtc: Rename HDMI encoder type to HDMI0 Maxime Ripard
2020-02-24  9:06 ` [PATCH 56/89] drm/vc4: crtc: Add HDMI1 encoder type Maxime Ripard
2020-02-24  9:06 ` [PATCH 57/89] drm/vc4: crtc: Remove redundant call to drm_crtc_enable_color_mgmt Maxime Ripard
2020-02-24  9:07 ` [PATCH 58/89] drm/vc4: crtc: Disable color management for HVS5 Maxime Ripard
2020-02-24  9:07 ` [PATCH 59/89] dt-bindings: display: vc4: pv: Add BCM2711 pixel valves Maxime Ripard
2020-02-25 18:19   ` Rob Herring
2020-02-24  9:07 ` [PATCH 60/89] drm/vc4: crtc: Add BCM2711 pixelvalves Maxime Ripard
2020-02-24  9:07 ` [PATCH 61/89] drm/vc4: hdmi: Use debugfs private field Maxime Ripard
2020-02-24  9:07 ` [PATCH 62/89] drm/vc4: hdmi: Move structure to header Maxime Ripard
2020-02-24  9:07 ` [PATCH 63/89] drm/vc4: hdmi: rework connectors and encoders Maxime Ripard
2020-02-24  9:07 ` [PATCH 64/89] drm/vc4: hdmi: Remove DDC argument to connector_init Maxime Ripard
2020-02-24  9:07 ` [PATCH 65/89] drm/vc4: hdmi: Rename hdmi to vc4_hdmi Maxime Ripard
2020-02-24  9:07 ` [PATCH 66/89] drm/vc4: hdmi: Move accessors " Maxime Ripard
2020-02-24  9:07 ` [PATCH 67/89] drm/vc4: hdmi: Use local vc4_hdmi directly Maxime Ripard
2020-02-24  9:07 ` [PATCH 68/89] drm/vc4: hdmi: Add container_of macros for encoders and connectors Maxime Ripard
2020-02-24  9:07 ` [PATCH 69/89] drm/vc4: hdmi: Pass vc4_hdmi to CEC code Maxime Ripard
2020-02-24  9:07 ` [PATCH 70/89] drm/vc4: hdmi: Remove vc4_dev hdmi pointer Maxime Ripard
2020-02-24  9:07 ` [PATCH 71/89] drm/vc4: hdmi: Remove vc4_hdmi_connector Maxime Ripard
2020-02-24  9:07 ` [PATCH 72/89] drm/vc4: hdmi: Introduce resource init and variant Maxime Ripard
2020-02-24  9:07 ` [PATCH 73/89] drm/vc4: hdmi: Implement a register layout abstraction Maxime Ripard
2020-02-24  9:07 ` [PATCH 74/89] drm/vc4: hdmi: Add reset callback Maxime Ripard
2020-02-24  9:07 ` [PATCH 75/89] drm/vc4: hdmi: Add PHY init and disable function Maxime Ripard
2020-02-24  9:07 ` [PATCH 76/89] drm/vc4: hdmi: Add PHY RNG enable / " Maxime Ripard
2020-02-24  9:07 ` [PATCH 77/89] drm/vc4: hdmi: Add a CSC setup callback Maxime Ripard
2020-02-24  9:07 ` [PATCH 78/89] drm/vc4: hdmi: Add a set_timings callback Maxime Ripard
2020-02-24  9:07 ` [PATCH 79/89] drm/vc4: hdmi: Add HDMI ID Maxime Ripard
2020-02-24  9:07 ` [PATCH 80/89] drm/vc4: hdmi: Deal with multiple debugfs files Maxime Ripard
2020-02-24  9:07 ` [PATCH 81/89] drm/vc4: hdmi: Add an audio support flag Maxime Ripard
2020-02-24  9:07 ` [PATCH 82/89] drm/vc4: hdmi: Move CEC init to its own function Maxime Ripard
2020-02-24  9:07 ` [PATCH 83/89] drm/vc4: hdmi: Add CEC support flag Maxime Ripard
2020-02-24  9:07 ` [PATCH 84/89] drm/vc4: hdmi: Remove unused CEC_CLOCK_DIV define Maxime Ripard
2020-02-24  9:07 ` [PATCH 85/89] drm/vc4: hdmi: Rename drm_encoder pointer in mode_valid Maxime Ripard
2020-02-24  9:07 ` [PATCH 86/89] drm/vc4: hdmi: Adjust HSM clock rate depending on pixel rate Maxime Ripard
2020-03-16 12:54   ` Nicolas Saenz Julienne
2020-02-24  9:07 ` [PATCH 87/89] drm/vc4: hdmi: Support the BCM2711 HDMI controllers Maxime Ripard
2020-03-17 18:25   ` Daniel Rodriguez
2020-02-24  9:07 ` [PATCH 88/89] dt-bindings: display: vc4: hdmi: Add BCM2711 HDMI controllers bindings Maxime Ripard
2020-02-25 18:24   ` Rob Herring
2020-02-24  9:07 ` [PATCH 89/89] ARM: dts: bcm2711: Enable the display pipeline Maxime Ripard
2020-03-05 10:00 ` [PATCH 70/89] drm/vc4: hdmi: Remove vc4_dev hdmi pointer Jian-Hong Pan

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