bcm27xx: add support for linux v5.15

Build system: x86_64
Build-tested: bcm2708, bcm2709, bcm2710, bcm2711
Run-tested: bcm2708/RPiB+, bcm2709/RPi3B, bcm2710/RPi3B, bcm2711/RPi4B

Signed-off-by: Marty Jones <mj8263788@gmail.com>
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>

1 files changed, 69 insertions, 0 deletions

diff --git a/target/linux/bcm27xx/patches-5.15/950-0859-clk-bcm-rpi-Set-a-default-minimum-rate.patch b/target/linux/bcm27xx/patches-5.15/950-0859-clk-bcm-rpi-Set-a-default-minimum-rate.patch
new file mode 100644
index 0000000000..dfa68383d5
--- /dev/null
+++ b/target/linux/bcm27xx/patches-5.15/950-0859-clk-bcm-rpi-Set-a-default-minimum-rate.patch
@@ -0,0 +1,69 @@
+From ac0b202c0bae166810c63e2ac5067b6ea3f4af43 Mon Sep 17 00:00:00 2001
+From: Maxime Ripard <maxime@cerno.tech>
+Date: Mon, 17 Jan 2022 17:31:06 +0100
+Subject: [PATCH] clk: bcm: rpi: Set a default minimum rate
+
+The M2MC clock provides the state machine clock for both HDMI
+controllers.
+
+However, if no HDMI monitor is plugged in at boot, its clock rate will
+be left at 0 by the firmware and will make any register access end up in
+a CPU stall, even though the clock was enabled.
+
+We had some code in the HDMI controller to deal with this before, but it
+makes more sense to have it in the clock driver. Move it there.
+
+Signed-off-by: Maxime Ripard <maxime@cerno.tech>
+---
+ drivers/clk/bcm/clk-raspberrypi.c | 26 ++++++++++++++++++++++++++
+ 1 file changed, 26 insertions(+)
+
+--- a/drivers/clk/bcm/clk-raspberrypi.c
++++ b/drivers/clk/bcm/clk-raspberrypi.c
+@@ -78,6 +78,7 @@ struct raspberrypi_clk_data {
+ struct raspberrypi_clk_variant {
+ 	bool		export;
+ 	char		*clkdev;
++	unsigned long	min_rate;
+ };
+ 
+ static struct raspberrypi_clk_variant
+@@ -91,6 +92,18 @@ raspberrypi_clk_variants[RPI_FIRMWARE_NU
+ 	},
+ 	[RPI_FIRMWARE_M2MC_CLK_ID] = {
+ 		.export = true,
++
++		/*
++		 * If we boot without any cable connected to any of the
++		 * HDMI connector, the firmware will skip the HSM
++		 * initialization and leave it with a rate of 0,
++		 * resulting in a bus lockup when we're accessing the
++		 * registers even if it's enabled.
++		 *
++		 * Let's put a sensible default so that we don't end up
++		 * in this situation.
++		 */
++		.min_rate = 120000000,
+ 	},
+ 	[RPI_FIRMWARE_V3D_CLK_ID] = {
+ 		.export = true,
+@@ -278,6 +291,19 @@ static struct clk_hw *raspberrypi_clk_re
+ 		}
+ 	}
+ 
++	if (variant->min_rate) {
++		unsigned long rate;
++
++		clk_hw_set_rate_range(&data->hw, variant->min_rate, max_rate);
++
++		rate = raspberrypi_fw_get_rate(&data->hw, 0);
++		if (rate < variant->min_rate) {
++			ret = raspberrypi_fw_set_rate(&data->hw, variant->min_rate, 0);
++			if (ret)
++				return ERR_PTR(ret);
++		}
++	}
++
+ 	return &data->hw;
+ }
+