Commit 542acfec authored by Maxime Ripard's avatar Maxime Ripard Committed by Stephen Boyd
Browse files

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: default avatarMaxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220225143534.405820-10-maxime@cerno.tech


Signed-off-by: default avatarStephen Boyd <sboyd@kernel.org>
parent 12c90f3f

drivers/clk/bcm/clk-raspberrypi.c

+26 −0
Original line number Diff line number Diff line
@@ -76,6 +76,7 @@ struct raspberrypi_clk_data { 
struct raspberrypi_clk_variant {

	bool		export;

	char		*clkdev;

	unsigned long	min_rate;

};



static struct raspberrypi_clk_variant
@@ -89,6 +90,18 @@ raspberrypi_clk_variants[RPI_FIRMWARE_NUM_CLK_ID] = { 
	},

	[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,
@@ -267,6 +280,19 @@ static struct clk_hw *raspberrypi_clk_register(struct raspberrypi_clk *rpi, 
		}

	}



	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;

}