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Subject: Re: [PATCH v12 3/9] drivers: memory: extend of_memory by LPDDR3
 support
To:     Krzysztof Kozlowski <krzk@kernel.org>
Cc:     devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-pm@vger.kernel.org,
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From:   Lukasz Luba <l.luba@partner.samsung.com>
Message-ID: <21d22ba6-2254-ae5e-7ef4-5dfaa3f54229@partner.samsung.com>
Date:   Wed, 21 Aug 2019 11:17:27 +0200
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Hi Krzysztof,

On 7/24/19 1:31 PM, Krzysztof Kozlowski wrote:
> 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?
The comment failed to stand the test of time, not for the first time
though. I will update it according to the current struct.

> 
>> + */
>> +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.
OK, thank you. I will change the print.

Thank you for the review.

Regards,
Lukasz
> 
> Best regards,
> Krzysztof
> 
>