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Date:   Wed, 28 Jul 2021 11:58:23 -0600
From:   Mathieu Poirier <mathieu.poirier@linaro.org>
To:     Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc:     linux-remoteproc@vger.kernel.org,
        linux-amlogic@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        bjorn.andersson@linaro.org, ohad@wizery.com
Subject: Re: [PATCH v3 2/2] remoteproc: meson-mx-ao-arc: Add a driver for the
 AO ARC remote procesor
Message-ID: <20210728175823.GA2766167@p14s>
References: <20210717234859.351911-1-martin.blumenstingl@googlemail.com>
 <20210717234859.351911-3-martin.blumenstingl@googlemail.com>
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In-Reply-To: <20210717234859.351911-3-martin.blumenstingl@googlemail.com>
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Hi Martin,

On Sun, Jul 18, 2021 at 01:48:59AM +0200, Martin Blumenstingl wrote:
> Amlogic Meson6, Meson8, Meson8b and Meson8m2 embed an ARC core in the
> Always-On (AO) power-domain. This is typically used for waking up the
> ARM cores after system suspend.
> 
> The configuration is spread across three different registers:
> - AO_REMAP_REG0 which must be programmed to zero, it's actual purpose
>   is unknown. There is a second remap register which is not used in the
>   vendor kernel (which served as reference for this driver).
> - AO_CPU_CNTL is used to start and stop the ARC core.
> - AO_SECURE_REG0 in the SECBUS2 register area with unknown purpose.
> 
> To boot the ARC core we also need to enable it's gate clock and trigger
> a reset.
> 
> The actual code for this ARC core can come from an ELF binary, for
> example by building the Zephyr RTOS for an ARC EM4 core and then taking
> "zephyr.elf" as firmware. This executable does not have any "rsc table"
> so we are skipping rproc_elf_load_rsc_table (rproc_ops.parse_fw) and
> rproc_elf_find_loaded_rsc_table (rproc_ops.find_loaded_rsc_table).
> 
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> ---
>  drivers/remoteproc/Kconfig           |  11 ++
>  drivers/remoteproc/Makefile          |   1 +
>  drivers/remoteproc/meson_mx_ao_arc.c | 260 +++++++++++++++++++++++++++
>  3 files changed, 272 insertions(+)
>  create mode 100644 drivers/remoteproc/meson_mx_ao_arc.c
> 
> diff --git a/drivers/remoteproc/Kconfig b/drivers/remoteproc/Kconfig
> index 9a6eedc3994a..3197bbe38785 100644
> --- a/drivers/remoteproc/Kconfig
> +++ b/drivers/remoteproc/Kconfig
> @@ -127,6 +127,17 @@ config KEYSTONE_REMOTEPROC
>  	  It's safe to say N here if you're not interested in the Keystone
>  	  DSPs or just want to use a bare minimum kernel.
>  
> +config MESON_MX_AO_ARC_REMOTEPROC
> +	tristate "Amlogic Meson6/8/8b/8m2 AO ARC remote processor support"
> +	depends on HAS_IOMEM
> +	depends on (ARM && ARCH_MESON) || COMPILE_TEST
> +	select GENERIC_ALLOCATOR
> +	help
> +	  Say m or y here to have support for the AO ARC remote processor
> +	  on Amlogic Meson6/Meson8/Meson8b/Meson8m2 SoCs. This is
> +	  typically used for system suspend.
> +	  If unusre say N.

s/unusre/unsure

> +
>  config PRU_REMOTEPROC
>  	tristate "TI PRU remoteproc support"
>  	depends on TI_PRUSS
> diff --git a/drivers/remoteproc/Makefile b/drivers/remoteproc/Makefile
> index bb26c9e4ef9c..ce1abeb30907 100644
> --- a/drivers/remoteproc/Makefile
> +++ b/drivers/remoteproc/Makefile
> @@ -18,6 +18,7 @@ obj-$(CONFIG_OMAP_REMOTEPROC)		+= omap_remoteproc.o
>  obj-$(CONFIG_WKUP_M3_RPROC)		+= wkup_m3_rproc.o
>  obj-$(CONFIG_DA8XX_REMOTEPROC)		+= da8xx_remoteproc.o
>  obj-$(CONFIG_KEYSTONE_REMOTEPROC)	+= keystone_remoteproc.o
> +obj-$(CONFIG_MESON_MX_AO_ARC_REMOTEPROC)+= meson_mx_ao_arc.o
>  obj-$(CONFIG_PRU_REMOTEPROC)		+= pru_rproc.o
>  obj-$(CONFIG_QCOM_PIL_INFO)		+= qcom_pil_info.o
>  obj-$(CONFIG_QCOM_RPROC_COMMON)		+= qcom_common.o
> diff --git a/drivers/remoteproc/meson_mx_ao_arc.c b/drivers/remoteproc/meson_mx_ao_arc.c
> new file mode 100644
> index 000000000000..86c0f3e48701
> --- /dev/null
> +++ b/drivers/remoteproc/meson_mx_ao_arc.c
> @@ -0,0 +1,260 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2020 Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/bitops.h>
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/property.h>
> +#include <linux/genalloc.h>
> +#include <linux/io.h>
> +#include <linux/ioport.h>

Not sure this is needed.

> +#include <linux/mfd/syscon.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/remoteproc.h>
> +#include <linux/reset.h>
> +#include <linux/sizes.h>
> +
> +#include "remoteproc_internal.h"
> +
> +#define AO_REMAP_REG0						0x0
> +#define AO_REMAP_REG0_REMAP_AHB_SRAM_BITS_17_14_FOR_ARM_CPU	GENMASK(3, 0)
> +
> +#define AO_REMAP_REG1						0x4
> +#define AO_REMAP_REG1_MOVE_AHB_SRAM_TO_0X0_INSTEAD_OF_DDR	BIT(4)
> +#define AO_REMAP_REG1_REMAP_AHB_SRAM_BITS_17_14_FOR_MEDIA_CPU	GENMASK(3, 0)
> +
> +#define AO_CPU_CNTL						0x0
> +#define AO_CPU_CNTL_AHB_SRAM_BITS_31_20				GENMASK(28, 16)
> +#define AO_CPU_CNTL_HALT					BIT(9)
> +#define AO_CPU_CNTL_UNKNONWN					BIT(8)
> +#define AO_CPU_CNTL_RUN						BIT(0)
> +
> +#define AO_CPU_STAT						0x4
> +
> +#define AO_SECURE_REG0						0x0
> +#define AO_SECURE_REG0_AHB_SRAM_BITS_19_12			GENMASK(15, 8)
> +
> +/* Only bits [31:20] and [17:14] are usable, all other bits must be zero */
> +#define MESON_AO_RPROC_SRAM_USABLE_BITS				0xfff3c000
> +
> +#define MESON_AO_RPROC_MEMORY_OFFSET				0x10000000
> +
> +struct meson_mx_ao_arc_rproc_priv {
> +	void __iomem		*remap_base;
> +	void __iomem		*cpu_base;
> +	unsigned long		sram_va;
> +	phys_addr_t		sram_pa;
> +	size_t			sram_size;
> +	struct gen_pool		*sram_pool;
> +	struct reset_control	*arc_reset;
> +	struct clk		*arc_pclk;
> +	struct regmap		*secbus2_regmap;
> +};
> +
> +static int meson_mx_ao_arc_rproc_start(struct rproc *rproc)
> +{
> +	struct meson_mx_ao_arc_rproc_priv *priv = rproc->priv;
> +	phys_addr_t translated_sram_addr;
> +	int ret;
> +
> +	ret = clk_prepare_enable(priv->arc_pclk);
> +	if (ret)
> +		return ret;
> +
> +	writel(FIELD_PREP(AO_REMAP_REG0_REMAP_AHB_SRAM_BITS_17_14_FOR_ARM_CPU,
> +			       priv->sram_pa >> 14),

Indentation problem

> +	       priv->remap_base + AO_REMAP_REG0);
> +
> +	/*
> +	 * The SRAM content as seen by the ARC core always starts at 0x0
> +	 * regardless of the value given here (this was discovered by trial and
> +	 * error). For SoCs older than Meson6 we probably have to set
> +	 * AO_REMAP_REG1_MOVE_AHB_SRAM_TO_0X0_INSTEAD_OF_DDR to achieve the
> +	 * same. (At least) For Meson8 and newer that bit must not be set.
> +	 */
> +	writel(0x0, priv->remap_base + AO_REMAP_REG1);
> +
> +	regmap_update_bits(priv->secbus2_regmap, AO_SECURE_REG0,
> +			   AO_SECURE_REG0_AHB_SRAM_BITS_19_12,
> +			   FIELD_PREP(AO_SECURE_REG0_AHB_SRAM_BITS_19_12,
> +				      priv->sram_pa >> 12));
> +
> +	ret = reset_control_reset(priv->arc_reset);
> +	if (ret) {
> +		clk_disable_unprepare(priv->arc_pclk);
> +		return ret;
> +	}
> +
> +	usleep_range(10, 100);

I've seen this kind of mysterious timeouts in other patchset based vendor trees.
You likely don't know why it is needed so I won't ask.

> +
> +	/*
> +	 * Convert from 0xd9000000 to 0xc9000000 as the vendor driver does.
> +	 * This only seems to be relevant for the AO_CPU_CNTL register. It is
> +	 * unknown why this is needed.
> +	 */
> +	translated_sram_addr = priv->sram_pa - MESON_AO_RPROC_MEMORY_OFFSET;
> +
> +	writel(FIELD_PREP(AO_CPU_CNTL_AHB_SRAM_BITS_31_20,
> +			  translated_sram_addr >> 20) |
> +	       AO_CPU_CNTL_UNKNONWN |
> +	       AO_CPU_CNTL_RUN,
> +	       priv->cpu_base + AO_CPU_CNTL);
> +	usleep_range(20, 200);
> +
> +	return 0;
> +}
> +
> +static int meson_mx_ao_arc_rproc_stop(struct rproc *rproc)
> +{
> +	struct meson_mx_ao_arc_rproc_priv *priv = rproc->priv;
> +
> +	writel(AO_CPU_CNTL_HALT, priv->cpu_base + AO_CPU_CNTL);
> +
> +	clk_disable_unprepare(priv->arc_pclk);
> +
> +	return 0;
> +}
> +
> +static void *meson_mx_ao_arc_rproc_da_to_va(struct rproc *rproc, u64 da,
> +					    size_t len, bool *is_iomem)
> +{
> +	struct meson_mx_ao_arc_rproc_priv *priv = rproc->priv;
> +
> +	if ((da + len) > priv->sram_size)
> +		return NULL;

I know from your comment in meson_mx_ao_arc_rproc_start() that the remote
processor's view of the SRAM is always mapped to 0.  Had I not read this driver
from top to bottom I'd find the above very perplexing.  Please add a comment.

> +
> +	return (void *)priv->sram_va + da;
> +}
> +
> +static struct rproc_ops meson_mx_ao_arc_rproc_ops = {
> +	.start		= meson_mx_ao_arc_rproc_start,
> +	.stop		= meson_mx_ao_arc_rproc_stop,
> +	.da_to_va	= meson_mx_ao_arc_rproc_da_to_va,
> +	.get_boot_addr	= rproc_elf_get_boot_addr,
> +	.load		= rproc_elf_load_segments,
> +	.sanity_check	= rproc_elf_sanity_check,
> +};
> +
> +static int meson_mx_ao_arc_rproc_probe(struct platform_device *pdev)
> +{
> +	struct meson_mx_ao_arc_rproc_priv *priv;
> +	struct device *dev = &pdev->dev;
> +	const char *fw_name = NULL;
> +	struct rproc *rproc;
> +	int ret;
> +
> +	device_property_read_string(dev, "firmware-name", &fw_name);
> +
> +	rproc = devm_rproc_alloc(dev, "meson-mx-ao-arc",
> +				 &meson_mx_ao_arc_rproc_ops, fw_name,
> +				 sizeof(*priv));
> +	if (!rproc)
> +		return -ENOMEM;
> +
> +	rproc->has_iommu = false;
> +	priv = rproc->priv;
> +
> +	priv->sram_pool = of_gen_pool_get(dev->of_node, "sram", 0);
> +	if (!priv->sram_pool) {
> +		dev_err(dev, "Could not get SRAM pool\n");
> +		return -ENODEV;
> +	}
> +
> +	priv->sram_size = gen_pool_avail(priv->sram_pool);
> +
> +	priv->sram_va = gen_pool_alloc(priv->sram_pool, priv->sram_size);
> +	if (!priv->sram_va) {
> +		dev_err(dev, "Could not alloc memory in SRAM pool\n");
> +		return -ENOMEM;
> +	}
> +
> +	priv->sram_pa = gen_pool_virt_to_phys(priv->sram_pool, priv->sram_va);
> +	if (priv->sram_pa & ~MESON_AO_RPROC_SRAM_USABLE_BITS) {
> +		dev_err(dev, "SRAM address contains unusable bits\n");
> +		ret = -EINVAL;
> +		goto err_free_genpool;
> +	}
> +
> +	priv->secbus2_regmap = syscon_regmap_lookup_by_phandle(dev->of_node,
> +							       "amlogic,secbus2");
> +	if (IS_ERR(priv->secbus2_regmap)) {
> +		dev_err(dev, "Failed to find SECBUS2 regmap\n");
> +		ret = PTR_ERR(priv->secbus2_regmap);
> +		goto err_free_genpool;
> +	}
> +
> +	priv->remap_base = devm_platform_ioremap_resource_byname(pdev, "remap");
> +	if (IS_ERR(priv->remap_base)) {
> +		ret = PTR_ERR(priv->remap_base);
> +		goto err_free_genpool;
> +	}
> +
> +	priv->cpu_base = devm_platform_ioremap_resource_byname(pdev, "cpu");
> +	if (IS_ERR(priv->cpu_base)) {
> +		ret = PTR_ERR(priv->cpu_base);
> +		goto err_free_genpool;
> +	}
> +
> +	priv->arc_reset = devm_reset_control_get_exclusive(dev, NULL);
> +	if (IS_ERR(priv->arc_reset)) {

Function __reset_control_get() in __devm_reset_control_get() can return NULL so
this should be IS_ERR_OR_NULL().

> +		dev_err(dev, "Failed to get ARC reset\n");
> +		ret = PTR_ERR(priv->arc_reset);
> +		goto err_free_genpool;
> +	}
> +
> +	priv->arc_pclk = devm_clk_get(dev, NULL);
> +	if (IS_ERR(priv->arc_pclk)) {
> +		dev_err(dev, "Failed to get the ARC PCLK\n");
> +		ret = PTR_ERR(priv->arc_pclk);
> +		goto err_free_genpool;
> +	}
> +
> +	platform_set_drvdata(pdev, rproc);
> +
> +	ret = rproc_add(rproc);
> +	if (ret)
> +		goto err_free_genpool;
> +
> +	return 0;
> +
> +err_free_genpool:
> +	gen_pool_free(priv->sram_pool, priv->sram_va, priv->sram_size);
> +	return ret;
> +}
> +
> +static int meson_mx_ao_arc_rproc_remove(struct platform_device *pdev)
> +{
> +	struct rproc *rproc = platform_get_drvdata(pdev);
> +	struct meson_mx_ao_arc_rproc_priv *priv = rproc->priv;
> +
> +	rproc_del(rproc);
> +	gen_pool_free(priv->sram_pool, priv->sram_va, priv->sram_size);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id meson_mx_ao_arc_rproc_match[] = {
> +	{ .compatible = "amlogic,meson8-ao-arc" },
> +	{ .compatible = "amlogic,meson8b-ao-arc" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, meson_mx_ao_arc_rproc_match);
> +
> +static struct platform_driver meson_mx_ao_arc_rproc_driver = {
> +	.probe = meson_mx_ao_arc_rproc_probe,
> +	.remove = meson_mx_ao_arc_rproc_remove,
> +	.driver = {
> +		.name = "meson-mx-ao-arc-rproc",
> +		.of_match_table = meson_mx_ao_arc_rproc_match,
> +	},
> +};
> +module_platform_driver(meson_mx_ao_arc_rproc_driver);

This driver is squeaky clean. With the above:

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>

> +
> +MODULE_DESCRIPTION("Amlogic Meson6/8/8b/8m2 AO ARC remote processor driver");
> +MODULE_AUTHOR("Martin Blumenstingl <martin.blumenstingl@googlemail.com>");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.32.0
>