Re: [PATCH v3 09/13] memory: tegra: Add API needed by the EMC driver

[Alexandre Courbot]

On 10/30/2014 01:22 AM, Tomeu Vizoso wrote:
> From: Mikko Perttunen <mperttunen@xxxxxxxxxx>
>
> The EMC driver needs to know the number of external memory devices and also
> needs to update the EMEM configuration based on the new rate of the memory bus.
>
> To know how to update the EMEM config, looks up the values of the burst regs in
> the DT, for a given timing.
>
> Signed-off-by: Mikko Perttunen <mperttunen@xxxxxxxxxx>
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
> ---
>   drivers/memory/tegra/tegra-mc.c | 172 ++++++++++++++++++++++++++++++++++++++++
>   include/soc/tegra/memory.h      |  17 ++++
>   2 files changed, 189 insertions(+)
>   create mode 100644 include/soc/tegra/memory.h
>
> diff --git a/drivers/memory/tegra/tegra-mc.c b/drivers/memory/tegra/tegra-mc.c
> index 0f0c8be..15ec018 100644
> --- a/drivers/memory/tegra/tegra-mc.c
> +++ b/drivers/memory/tegra/tegra-mc.c
> @@ -16,8 +16,10 @@
>   #include <linux/of_platform.h>
>   #include <linux/platform_device.h>
>   #include <linux/slab.h>
> +#include <linux/sort.h>
>
>   #include <soc/tegra/ahb.h>
> +#include <soc/tegra/fuse.h>
>
>   #include "tegra-mc.h"
>
> @@ -53,8 +55,59 @@
>   #define  MC_EMEM_ARB_CFG_CYCLES_PER_UPDATE_MASK	0x1ff
>   #define MC_EMEM_ARB_MISC0 0xd8
>
> +#define MC_EMEM_ARB_CFG				0x90
> +#define MC_EMEM_ARB_OUTSTANDING_REQ		0x94
> +#define MC_EMEM_ARB_TIMING_RCD			0x98
> +#define MC_EMEM_ARB_TIMING_RP			0x9c
> +#define MC_EMEM_ARB_TIMING_RC			0xa0
> +#define MC_EMEM_ARB_TIMING_RAS			0xa4
> +#define MC_EMEM_ARB_TIMING_FAW			0xa8
> +#define MC_EMEM_ARB_TIMING_RRD			0xac
> +#define MC_EMEM_ARB_TIMING_RAP2PRE		0xb0
> +#define MC_EMEM_ARB_TIMING_WAP2PRE		0xb4
> +#define MC_EMEM_ARB_TIMING_R2R			0xb8
> +#define MC_EMEM_ARB_TIMING_W2W			0xbc
> +#define MC_EMEM_ARB_TIMING_R2W			0xc0
> +#define MC_EMEM_ARB_TIMING_W2R			0xc4
> +#define MC_EMEM_ARB_DA_TURNS			0xd0
> +#define MC_EMEM_ARB_DA_COVERS			0xd4
> +#define MC_EMEM_ARB_MISC0			0xd8
> +#define MC_EMEM_ARB_MISC1			0xdc
> +#define MC_EMEM_ARB_RING1_THROTTLE		0xe0
> +
> +#define MC_EMEM_ADR_CFG 0x54
> +#define MC_EMEM_ADR_CFG_EMEM_NUMDEV BIT(0)
> +
>   struct tegra_smmu;
>
> +static int t124_mc_burst_regs[] = {
> +	MC_EMEM_ARB_CFG,
> +	MC_EMEM_ARB_OUTSTANDING_REQ,
> +	MC_EMEM_ARB_TIMING_RCD,
> +	MC_EMEM_ARB_TIMING_RP,
> +	MC_EMEM_ARB_TIMING_RC,
> +	MC_EMEM_ARB_TIMING_RAS,
> +	MC_EMEM_ARB_TIMING_FAW,
> +	MC_EMEM_ARB_TIMING_RRD,
> +	MC_EMEM_ARB_TIMING_RAP2PRE,
> +	MC_EMEM_ARB_TIMING_WAP2PRE,
> +	MC_EMEM_ARB_TIMING_R2R,
> +	MC_EMEM_ARB_TIMING_W2W,
> +	MC_EMEM_ARB_TIMING_R2W,
> +	MC_EMEM_ARB_TIMING_W2R,
> +	MC_EMEM_ARB_DA_TURNS,
> +	MC_EMEM_ARB_DA_COVERS,
> +	MC_EMEM_ARB_MISC0,
> +	MC_EMEM_ARB_MISC1,
> +	MC_EMEM_ARB_RING1_THROTTLE
> +};
> +
> +struct mc_timing {
> +	unsigned long rate;
> +
> +	u32 mc_burst_data[ARRAY_SIZE(t124_mc_burst_regs)];
> +};
> +
>   struct tegra_mc {
>   	struct device *dev;
>   	struct tegra_smmu *smmu;
> @@ -64,6 +117,9 @@ struct tegra_mc {
>
>   	const struct tegra_mc_soc *soc;
>   	unsigned long tick;
> +
> +	struct mc_timing *timings;
> +	unsigned int num_timings;
>   };
>
>   static inline u32 mc_readl(struct tegra_mc *mc, unsigned long offset)
> @@ -789,6 +845,37 @@ static const struct of_device_id tegra_mc_of_match[] = {
>   	{ }
>   };
>
> +void tegra_mc_write_emem_configuration(struct tegra_mc *mc, unsigned long rate)
> +{
> +	int i;
> +	struct mc_timing timing;
> +
> +	for (i = 0; i < mc->num_timings; ++i) {
> +		timing = mc->timings[i];
> +
> +		if (timing.rate == rate)
> +			break;
> +	}
> +
> +	if (i == mc->num_timings)
> +		return;

Mmm, this looks like an error, which we should probably report to the 
caller (and maybe the user too using dev_err()).

> +
> +	for (i = 0; i < ARRAY_SIZE(t124_mc_burst_regs); ++i)
> +		mc_writel(mc, timing.mc_burst_data[i], t124_mc_burst_regs[i]);
> +}
> +
> +int tegra_mc_get_emem_device_count(struct tegra_mc *mc)
> +{
> +	u8 dram_count;
> +
> +	dram_count = mc_readl(mc, MC_EMEM_ADR_CFG);
> +	dram_count &= MC_EMEM_ADR_CFG_EMEM_NUMDEV;
> +	dram_count++;
> +
> +	return dram_count;
> +}
> +
> +
>   /* XXX: provide prototype in public header */
>   int tegra_mc_set_bandwidth(struct tegra_mc *mc, unsigned int id,
>   			   unsigned long bandwidth)
> @@ -966,11 +1053,68 @@ static irqreturn_t tegra_mc_irq(int irq, void *data)
>   	return IRQ_HANDLED;
>   }
>
> +static int load_one_timing_from_dt(struct tegra_mc *mc,
> +				   struct mc_timing *timing,
> +				   struct device_node *node)
> +{
> +	int err;
> +	u32 tmp;
> +
> +	err = of_property_read_u32(node, "clock-frequency", &tmp);
> +	if (err) {
> +		dev_err(mc->dev,
> +			"timing %s: failed to read rate\n", node->name);
> +		return err;
> +	}
> +
> +	timing->rate = tmp;
> +
> +	err = of_property_read_u32_array(node, "nvidia,emem-configuration",
> +					 timing->mc_burst_data,
> +					 ARRAY_SIZE(timing->mc_burst_data));
> +	if (err) {
> +		dev_err(mc->dev,
> +			"timing %s: failed to read emc burst data\n",
> +			node->name);
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static int load_timings_from_dt(struct tegra_mc *mc,
> +				struct device_node *node)
> +{
> +	struct device_node *child;
> +	int child_count = of_get_child_count(node);
> +	int i = 0, err;
> +
> +	mc->timings = devm_kzalloc(mc->dev,
> +				      sizeof(struct mc_timing) * child_count,
> +				      GFP_KERNEL);
> +	if (!mc->timings)
> +		return -ENOMEM;
> +
> +	mc->num_timings = child_count;
> +
> +	for_each_child_of_node(node, child) {
> +		struct mc_timing *timing = mc->timings + (i++);

Parenthesis probably not needed here.

> +
> +		err = load_one_timing_from_dt(mc, timing, child);
> +		if (err)
> +			return err;
> +	}
> +
> +	return 0;
> +}
> +
>   static int tegra_mc_probe(struct platform_device *pdev)
>   {
>   	const struct of_device_id *match;
>   	struct resource *res;
>   	struct tegra_mc *mc;
> +	struct device_node *node;
> +	u32 ram_code, node_ram_code;
>   	u32 value;
>   	int err;
>
> @@ -1001,6 +1145,34 @@ static int tegra_mc_probe(struct platform_device *pdev)
>   		return PTR_ERR(mc->clk);
>   	}
>
> +	ram_code = tegra_read_ram_code();
> +
> +	mc->num_timings = 0;
> +
> +	for_each_child_of_node(pdev->dev.of_node, node) {
> +		if (strcmp(node->name, "timings"))
> +			continue;
> +
> +		err = of_property_read_u32(node, "nvidia,ram-code",
> +						&node_ram_code);
> +		if (err) {
> +			dev_warn(&pdev->dev,
> +				 "skipping timing without ram-code\n");
> +			continue;
> +		}
> +
> +		if (node_ram_code != ram_code)
> +			continue;
> +
> +		err = load_timings_from_dt(mc, node);
> +		if (err)
> +			return err;
> +		break;
> +	}
> +
> +	if (mc->num_timings == 0)
> +		dev_warn(&pdev->dev, "no memory timings registered\n");
> +
>   	err = tegra_mc_setup_latency_allowance(mc);
>   	if (err < 0) {
>   		dev_err(&pdev->dev, "failed to setup latency allowance: %d\n",
> diff --git a/include/soc/tegra/memory.h b/include/soc/tegra/memory.h
> new file mode 100644
> index 0000000..f307516
> --- /dev/null
> +++ b/include/soc/tegra/memory.h
> @@ -0,0 +1,17 @@
> +/*
> + * Copyright (C) 2014 NVIDIA Corporation
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#ifndef __SOC_TEGRA_MEMORY_H__
> +#define __SOC_TEGRA_MEMORY_H__
> +
> +struct tegra_mc;
> +
> +void tegra_mc_write_emem_configuration(struct tegra_mc *mc, unsigned long rate);
> +int tegra_mc_get_emem_device_count(struct tegra_mc *mc);
> +
> +#endif /* __SOC_TEGRA_MEMORY_H__ */

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