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From:   Krzysztof Kozlowski <krzk@kernel.org>
Date:   Wed, 24 Jul 2019 13:31:11 +0200
Message-ID: <CAJKOXPd96ExoCR-SiJfRqTbwO+_aQ6LSDVOQcrrt8JQHsoZBEw@mail.gmail.com>
Subject: Re: [PATCH v12 3/9] drivers: memory: extend of_memory by LPDDR3 support
To:     Lukasz Luba <l.luba@partner.samsung.com>
Cc:     devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-pm@vger.kernel.org,
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On Mon, 22 Jul 2019 at 11:47, Lukasz Luba <l.luba@partner.samsung.com> wrote:
>
> The patch adds AC timings information needed to support LPDDR3 and memory
> controllers. The structure is used in of_memory and currently in Exynos
> 5422 DMC. Add parsing data needed for LPDDR3 support.
> It is currently used in Exynos5422 Dynamic Memory Controller.
>
> Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
> Signed-off-by: Lukasz Luba <l.luba@partner.samsung.com>
> ---
>  drivers/memory/jedec_ddr.h |  61 +++++++++++++++
>  drivers/memory/of_memory.c | 154 +++++++++++++++++++++++++++++++++++++
>  drivers/memory/of_memory.h |  18 +++++
>  3 files changed, 233 insertions(+)
>
> diff --git a/drivers/memory/jedec_ddr.h b/drivers/memory/jedec_ddr.h
> index 4a21b5044ff8..38e26d461bdb 100644
> --- a/drivers/memory/jedec_ddr.h
> +++ b/drivers/memory/jedec_ddr.h
> @@ -29,6 +29,7 @@
>  #define DDR_TYPE_LPDDR2_S4     3
>  #define DDR_TYPE_LPDDR2_S2     4
>  #define DDR_TYPE_LPDDR2_NVM    5
> +#define DDR_TYPE_LPDDR3                6
>
>  /* DDR IO width */
>  #define DDR_IO_WIDTH_4         1
> @@ -169,4 +170,64 @@ extern const struct lpddr2_timings
>         lpddr2_jedec_timings[NUM_DDR_TIMING_TABLE_ENTRIES];
>  extern const struct lpddr2_min_tck lpddr2_jedec_min_tck;
>
> +/*
> + * Structure for timings for LPDDR3 based on LPDDR2 plus additional fields.
> + * All parameters are in pico seconds(ps) unless explicitly indicated
> + * with a suffix like tRAS_max_ns below

To which tRAS_max_ns are you referring?

> + */
> +struct lpddr3_timings {
> +       u32 max_freq;
> +       u32 min_freq;
> +       u32 tRFC;
> +       u32 tRRD;
> +       u32 tRPab;
> +       u32 tRPpb;
> +       u32 tRCD;
> +       u32 tRC;
> +       u32 tRAS;
> +       u32 tWTR;
> +       u32 tWR;
> +       u32 tRTP;
> +       u32 tW2W_C2C;
> +       u32 tR2R_C2C;
> +       u32 tWL;
> +       u32 tDQSCK;
> +       u32 tRL;
> +       u32 tFAW;
> +       u32 tXSR;
> +       u32 tXP;
> +       u32 tCKE;
> +       u32 tCKESR;
> +       u32 tMRD;
> +};
> +
> +/*
> + * Min value for some parameters in terms of number of tCK cycles(nCK)
> + * Please set to zero parameters that are not valid for a given memory
> + * type
> + */
> +struct lpddr3_min_tck {
> +       u32 tRFC;
> +       u32 tRRD;
> +       u32 tRPab;
> +       u32 tRPpb;
> +       u32 tRCD;
> +       u32 tRC;
> +       u32 tRAS;
> +       u32 tWTR;
> +       u32 tWR;
> +       u32 tRTP;
> +       u32 tW2W_C2C;
> +       u32 tR2R_C2C;
> +       u32 tWL;
> +       u32 tDQSCK;
> +       u32 tRL;
> +       u32 tFAW;
> +       u32 tXSR;
> +       u32 tXP;
> +       u32 tCKE;
> +       u32 tCKESR;
> +       u32 tMRD;
> +};
> +
>  #endif /* __JEDEC_DDR_H */
> diff --git a/drivers/memory/of_memory.c b/drivers/memory/of_memory.c
> index 46539b27a3fb..4f5b8c81669f 100644
> --- a/drivers/memory/of_memory.c
> +++ b/drivers/memory/of_memory.c
> @@ -3,6 +3,12 @@
>   * OpenFirmware helpers for memory drivers
>   *
>   * Copyright (C) 2012 Texas Instruments, Inc.
> + * Copyright (C) 2019 Samsung Electronics Co., Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
>   */
>
>  #include <linux/device.h>
> @@ -149,3 +155,151 @@ const struct lpddr2_timings *of_get_ddr_timings(struct device_node *np_ddr,
>         return lpddr2_jedec_timings;
>  }
>  EXPORT_SYMBOL(of_get_ddr_timings);
> +
> +/**
> + * of_lpddr3_get_min_tck() - extract min timing values for lpddr3
> + * @np: pointer to ddr device tree node
> + * @device: device requesting for min timing values
> + *
> + * Populates the lpddr3_min_tck structure by extracting data
> + * from device tree node. Returns a pointer to the populated
> + * structure. If any error in populating the structure, returns NULL.
> + */
> +const struct lpddr3_min_tck *of_lpddr3_get_min_tck(struct device_node *np,
> +                                                  struct device *dev)
> +{
> +       int                     ret = 0;
> +       struct lpddr3_min_tck   *min;
> +
> +       min = devm_kzalloc(dev, sizeof(*min), GFP_KERNEL);
> +       if (!min)
> +               goto default_min_tck;
> +
> +       ret |= of_property_read_u32(np, "tRFC-min-tck", &min->tRFC);
> +       ret |= of_property_read_u32(np, "tRRD-min-tck", &min->tRRD);
> +       ret |= of_property_read_u32(np, "tRPab-min-tck", &min->tRPab);
> +       ret |= of_property_read_u32(np, "tRPpb-min-tck", &min->tRPpb);
> +       ret |= of_property_read_u32(np, "tRCD-min-tck", &min->tRCD);
> +       ret |= of_property_read_u32(np, "tRC-min-tck", &min->tRC);
> +       ret |= of_property_read_u32(np, "tRAS-min-tck", &min->tRAS);
> +       ret |= of_property_read_u32(np, "tWTR-min-tck", &min->tWTR);
> +       ret |= of_property_read_u32(np, "tWR-min-tck", &min->tWR);
> +       ret |= of_property_read_u32(np, "tRTP-min-tck", &min->tRTP);
> +       ret |= of_property_read_u32(np, "tW2W-C2C-min-tck", &min->tW2W_C2C);
> +       ret |= of_property_read_u32(np, "tR2R-C2C-min-tck", &min->tR2R_C2C);
> +       ret |= of_property_read_u32(np, "tWL-min-tck", &min->tWL);
> +       ret |= of_property_read_u32(np, "tDQSCK-min-tck", &min->tDQSCK);
> +       ret |= of_property_read_u32(np, "tRL-min-tck", &min->tRL);
> +       ret |= of_property_read_u32(np, "tFAW-min-tck", &min->tFAW);
> +       ret |= of_property_read_u32(np, "tXSR-min-tck", &min->tXSR);
> +       ret |= of_property_read_u32(np, "tXP-min-tck", &min->tXP);
> +       ret |= of_property_read_u32(np, "tCKE-min-tck", &min->tCKE);
> +       ret |= of_property_read_u32(np, "tCKESR-min-tck", &min->tCKESR);
> +       ret |= of_property_read_u32(np, "tMRD-min-tck", &min->tMRD);
> +
> +       if (ret) {
> +               dev_warn(dev, "%s: errors while parsing min-tck values\n",
> +                        __func__);
> +               devm_kfree(dev, min);
> +               goto default_min_tck;
> +       }
> +
> +       return min;
> +
> +default_min_tck:
> +       dev_warn(dev, "%s: using default min-tck values\n", __func__);

Here and later - you return NULL, not default values. Your driver -
consumer - also behaves like with error condition, not like with
default values. Print just that you cannot get timings, I guess.

Best regards,
Krzysztof