From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: Maxime Ripard <maxime@cerno.tech>
Cc: linux-rpi-kernel@lists.infradead.org,
bcm-kernel-feedback-list@broadcom.com,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Dave Stevenson <dave.stevenson@raspberrypi.com>,
Tim Gover <tim.gover@raspberrypi.com>,
Phil Elwell <phil@raspberrypi.com>,
Mike Turquette <mturquette@baylibre.com>,
Stephen Boyd <sboyd@kernel.org>,
linux-clk@vger.kernel.org
Subject: Re: [PATCH v4 21/27] clk: bcm: rpi: Discover the firmware clocks
Date: Thu, 11 Jun 2020 13:14:58 +0200 [thread overview]
Message-ID: <7cf4a213862145abd8e0368b669aab39112ffaeb.camel@suse.de> (raw)
In-Reply-To: <40ab5a9718000636a513d374e7579e2d2b57f961.1591860665.git-series.maxime@cerno.tech>
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On Thu, 2020-06-11 at 09:32 +0200, Maxime Ripard wrote:
> The RaspberryPi4 firmware actually exposes more clocks than are currently
> handled by the driver and we will need to change some of them directly
> based on the pixel rate for the display related clocks, or the load for the
> GPU.
>
> Since the firmware implements DVFS, this rate change can have a number of
> side-effects, including adjusting the various PLL voltages or the PLL
> parents. The firmware also implements thermal throttling, so even some
> thermal pressure can change those parameters behind Linux back.
>
> DVFS is currently implemented on the arm, core, h264, v3d, isp and hevc
> clocks, so updating any of them using the MMIO driver (and thus behind the
> firmware's back) can lead to troubles, the arm clock obviously being the
> most problematic.
>
> In order to make Linux play as nice as possible with those constraints, it
> makes sense to rely on the firmware clocks as much as possible. However,
> the firmware doesn't seem to provide some equivalents to their MMIO
> counterparts, so we can't really replace that driver entirely.
>
> Fortunately, the firmware has an interface to discover the clocks it
> exposes.
>
> Let's use it to discover, register the clocks in the clocks framework and
> then expose them through the device tree for consumers to use them.
>
> Cc: Michael Turquette <mturquette@baylibre.com>
> Cc: Stephen Boyd <sboyd@kernel.org>
> Cc: linux-clk@vger.kernel.org
> Reviewed-by: Stephen Boyd <sboyd@kernel.org>
> Signed-off-by: Maxime Ripard <maxime@cerno.tech>
> ---
Acked-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Regards,
Nicolas
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next prev parent reply other threads:[~2020-06-11 11:15 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-11 7:31 [PATCH v4 00/27] clk: bcm: rpi: Add support for BCM2711 " Maxime Ripard
2020-06-11 7:31 ` [PATCH v4 01/27] dt-bindings: arm: bcm: Convert BCM2835 firmware binding to YAML Maxime Ripard
2020-06-11 7:31 ` [PATCH v4 02/27] dt-bindings: clock: Add a binding for the RPi Firmware clocks Maxime Ripard
2020-06-11 7:31 ` [PATCH v4 03/27] firmware: rpi: Only create clocks device if we don't have a node for it Maxime Ripard
2020-06-11 7:31 ` [PATCH v4 04/27] clk: bcm: rpi: Allow the driver to be probed by DT Maxime Ripard
2020-06-11 7:31 ` [PATCH v4 05/27] clk: bcm: rpi: Statically init clk_init_data Maxime Ripard
2020-06-11 7:31 ` [PATCH v4 06/27] clk: bcm: rpi: Use clk_hw_register for pllb_arm Maxime Ripard
2020-06-11 7:31 ` [PATCH v4 07/27] clk: bcm: rpi: Remove global pllb_arm clock pointer Maxime Ripard
2020-06-11 7:31 ` [PATCH v4 08/27] clk: bcm: rpi: Make sure pllb_arm is removed Maxime Ripard
2020-06-11 7:31 ` [PATCH v4 09/27] clk: bcm: rpi: Remove pllb_arm_lookup global pointer Maxime Ripard
2020-06-11 7:31 ` [PATCH v4 10/27] clk: bcm: rpi: Switch to clk_hw_register_clkdev Maxime Ripard
2020-06-11 7:32 ` [PATCH v4 11/27] clk: bcm: rpi: Make sure the clkdev lookup is removed Maxime Ripard
2020-06-11 7:32 ` [PATCH v4 12/27] clk: bcm: rpi: Use CCF boundaries instead of rolling our own Maxime Ripard
2020-06-11 7:32 ` [PATCH v4 13/27] clk: bcm: rpi: Create a data structure for the clocks Maxime Ripard
2020-06-11 7:32 ` [PATCH v4 14/27] clk: bcm: rpi: Add clock id to data Maxime Ripard
2020-06-11 7:32 ` [PATCH v4 15/27] clk: bcm: rpi: Pass the clocks data to the firmware function Maxime Ripard
2020-06-11 7:32 ` [PATCH v4 16/27] clk: bcm: rpi: Rename is_prepared function Maxime Ripard
2020-06-11 7:32 ` [PATCH v4 17/27] clk: bcm: rpi: Split pllb clock hooks Maxime Ripard
2020-06-11 7:32 ` [PATCH v4 18/27] clk: bcm: rpi: Make the PLLB registration function return a clk_hw Maxime Ripard
2020-06-11 7:32 ` [PATCH v4 19/27] clk: bcm: rpi: Add DT provider for the clocks Maxime Ripard
2020-06-11 7:32 ` [PATCH v4 20/27] clk: bcm: rpi: Add an enum for the firmware clocks Maxime Ripard
2020-06-11 7:32 ` [PATCH v4 21/27] clk: bcm: rpi: Discover " Maxime Ripard
2020-06-11 11:14 ` Nicolas Saenz Julienne [this message]
2020-06-11 7:32 ` [PATCH v4 22/27] clk: bcm: rpi: Give firmware clocks a name Maxime Ripard
2020-06-11 7:32 ` [PATCH v4 23/27] Revert "clk: bcm2835: remove pllb" Maxime Ripard
2020-06-11 11:15 ` Nicolas Saenz Julienne
2020-06-11 7:32 ` [PATCH v4 24/27] ARM: dts: bcm2711: Add firmware clocks node Maxime Ripard
2020-06-11 7:32 ` [PATCH v4 25/27] clk: bcm2835: Allow custom CCF flags for the PLLs Maxime Ripard
2020-06-11 9:11 ` Nicolas Saenz Julienne
2020-06-11 7:32 ` [PATCH v4 26/27] clk: bcm2835: Don't cache the PLLB rate Maxime Ripard
2020-06-11 11:17 ` Nicolas Saenz Julienne
2020-06-11 7:32 ` [PATCH v4 27/27] clk: bcm: rpi: Remove the quirks for the CPU clock Maxime Ripard
2020-06-11 11:18 ` Nicolas Saenz Julienne
2020-06-11 11:21 ` [PATCH v4 00/27] clk: bcm: rpi: Add support for BCM2711 firmware clocks Nicolas Saenz Julienne
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