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Date: Wed, 24 Jun 2020 14:51:12 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: alexandru.tachici@...log.com
Cc: linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
devicetree@...r.kernel.org, robh+dt@...nel.org
Subject: Re: [PATCH v4 5/7] hwmon: pmbus: adm1266: read blackbox
On Tue, Jun 23, 2020 at 08:36:57PM +0300, alexandru.tachici@...log.com wrote:
> From: Alexandru Tachici <alexandru.tachici@...log.com>
>
> Use the nvmem kernel api to expose the black box
> chip functionality to userspace.
>
> Signed-off-by: Alexandru Tachici <alexandru.tachici@...log.com>
> ---
> drivers/hwmon/pmbus/adm1266.c | 134 ++++++++++++++++++++++++++++++++++
> 1 file changed, 134 insertions(+)
>
> diff --git a/drivers/hwmon/pmbus/adm1266.c b/drivers/hwmon/pmbus/adm1266.c
> index 0960ead8d96a..b9e92ab1e39a 100644
> --- a/drivers/hwmon/pmbus/adm1266.c
> +++ b/drivers/hwmon/pmbus/adm1266.c
> @@ -15,6 +15,8 @@
> #include <linux/init.h>
> #include <linux/kernel.h>
> #include <linux/module.h>
> +#include <linux/nvmem-consumer.h>
> +#include <linux/nvmem-provider.h>
> #include <linux/proc_fs.h>
> #include <linux/slab.h>
> #include <linux/uaccess.h>
> @@ -22,10 +24,13 @@
> #include <linux/adm1266.h>
> #include "pmbus.h"
>
> +#define ADM1266_BLACKBOX_CONFIG 0xD3
> #define ADM1266_PDIO_CONFIG 0xD4
> #define ADM1266_GO_COMMAND 0xD8
> #define ADM1266_READ_STATE 0xD9
> +#define ADM1266_READ_BLACKBOX 0xDE
> #define ADM1266_GPIO_CONFIG 0xE1
> +#define ADM1266_BLACKBOX_INFO 0xE6
> #define ADM1266_PDIO_STATUS 0xE9
> #define ADM1266_GPIO_STATUS 0xEA
>
> @@ -42,6 +47,9 @@
> #define ADM1266_PDIO_GLITCH_FILT(x) FIELD_GET(GENMASK(12, 9), x)
> #define ADM1266_PDIO_OUT_CFG(x) FIELD_GET(GENMASK(2, 0), x)
>
> +#define ADM1266_BLACKBOX_OFFSET 0x7F700
> +#define ADM1266_BLACKBOX_SIZE 64
> +
> #define ADM1266_PMBUS_BLOCK_MAX 255
>
> DECLARE_CRC8_TABLE(pmbus_crc_table);
> @@ -52,6 +60,17 @@ struct adm1266_data {
> const char *gpio_names[ADM1266_GPIO_NR + ADM1266_PDIO_NR];
> struct i2c_client *client;
> struct mutex ioctl_mutex; /* lock ioctl access */
> + struct nvmem_config nvmem_config;
> + struct nvmem_device *nvmem;
> + u8 *dev_mem;
> +};
> +
> +static const struct nvmem_cell_info adm1266_nvmem_cells[] = {
> + {
> + .name = "blackbox",
> + .offset = ADM1266_BLACKBOX_OFFSET,
> + .bytes = 2048,
> + },
> };
>
> /* Different from Block Read as it sends data and waits for the slave to
> @@ -404,6 +423,117 @@ static int adm1266_init_procfs(struct adm1266_data *data)
> return 0;
> }
>
> +static int adm1266_nvmem_read_blackbox(struct adm1266_data *data, u8 *buf)
> +{
> + u8 read_buf[5];
> + char index;
> + int record_count;
> + int ret;
> +
> + ret = i2c_smbus_read_block_data(data->client, ADM1266_BLACKBOX_INFO,
> + read_buf);
> + if (ret < 0)
> + return ret;
> +
> + record_count = read_buf[3];
> +
> + for (index = 0; index < record_count; index++) {
> + ret = pmbus_block_xfer(data->client, ADM1266_READ_BLACKBOX, 1,
> + &index, buf);
> + if (ret < 0)
> + return ret;
> +
> + buf += ADM1266_BLACKBOX_SIZE;
> + }
> +
> + return 0;
> +}
> +
> +static bool adm1266_cell_is_accessed(const struct nvmem_cell_info *mem_cell,
> + unsigned int offset, size_t bytes)
> +{
> + unsigned int start_addr = offset;
> + unsigned int end_addr = offset + bytes;
> + unsigned int cell_start = mem_cell->offset;
> + unsigned int cell_end = mem_cell->offset + mem_cell->bytes;
> +
> + if (start_addr <= cell_end && cell_start <= end_addr)
> + return true;
> +
> + return false;
return start_addr <= cell_end && cell_start <= end_add;
does the same.
> +}
> +
> +static int adm1266_read_mem_cell(struct adm1266_data *data,
> + const struct nvmem_cell_info *mem_cell)
> +{
> + u8 *mem_offset;
> + int ret;
> +
> + switch (mem_cell->offset) {
> + case ADM1266_BLACKBOX_OFFSET:
How would this ever have a different value ?
> + mem_offset = data->dev_mem + mem_cell->offset;
> + ret = adm1266_nvmem_read_blackbox(data, mem_offset);
> + if (ret)
> + dev_err(&data->client->dev, "Could not read blackbox!");
> + return ret;
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static int adm1266_nvmem_read(void *priv, unsigned int offset, void *val,
> + size_t bytes)
> +{
> + const struct nvmem_cell_info *mem_cell;
> + struct adm1266_data *data = priv;
> + int ret;
> + int i;
> +
> + for (i = 0; i < data->nvmem_config.ncells; i++) {
> + mem_cell = &adm1266_nvmem_cells[i];
> + if (!adm1266_cell_is_accessed(mem_cell, offset, bytes))
> + continue;
> +
> + ret = adm1266_read_mem_cell(data, mem_cell);
> + if (ret < 0)
> + return ret;
> + }
I am a bit puzzled about the complexity of this code.
Is there reason to believe that there will ever be more than one cell ?
If that is not the case, I don't see the value in the complexity.
If there is a plan to add more nvram cells later, it should be
mentioned somewhere. As it is, the code is difficult to understand,
and I really only want to spend time analyzing it if it is really
necessary.
> +
> + memcpy(val, data->dev_mem + offset, bytes);
> +
> + return 0;
> +}
> +
> +static int adm1266_config_nvmem(struct adm1266_data *data)
> +{
> + data->nvmem_config.name = dev_name(&data->client->dev);
> + data->nvmem_config.dev = &data->client->dev;
> + data->nvmem_config.root_only = true;
> + data->nvmem_config.read_only = true;
> + data->nvmem_config.owner = THIS_MODULE;
> + data->nvmem_config.reg_read = adm1266_nvmem_read;
> + data->nvmem_config.cells = adm1266_nvmem_cells;
> + data->nvmem_config.ncells = ARRAY_SIZE(adm1266_nvmem_cells);
> + data->nvmem_config.priv = data;
> + data->nvmem_config.stride = 1;
> + data->nvmem_config.word_size = 1;
> + data->nvmem_config.size = 0x80000;
> +
> + data->nvmem = nvmem_register(&data->nvmem_config);
If CONFIG_NVMEM is not enabled, this function will return -EOPNOTSUPP,
and the driver will fail to load. I don't think that is acceptable.
Also, this should really use devm_nvmem_register().
> + if (IS_ERR(data->nvmem)) {
> + dev_err(&data->client->dev, "Could not register nvmem!");
> + return PTR_ERR(data->nvmem);
> + }
> +
> + data->dev_mem = devm_kzalloc(&data->client->dev,
> + data->nvmem_config.size,
> + GFP_KERNEL);
This is at least potentially racy. Presumably nvram can be accessed right
after the call to nvmem_register(). If that happens, dev_mem is not yet
set, and the system will crash.
> + if (!data->dev_mem)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> static int adm1266_probe(struct i2c_client *client,
> const struct i2c_device_id *id)
> {
> @@ -430,6 +560,10 @@ static int adm1266_probe(struct i2c_client *client,
> if (ret < 0)
> return ret;
>
> + ret = adm1266_config_nvmem(data);
> + if (ret < 0)
> + return ret;
> +
> info = &data->info;
> info->pages = 17;
> info->format[PSC_VOLTAGE_OUT] = linear;
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