target/linux/bcm27xx/patches-5.4/950-0767-w1_therm-fix-reset_select_slave-during-discovery.patch

   1 From dfc9fd0060f9103ca1f9335d529401ee8a105737 Mon Sep 17 00:00:00 2001
   2 From: Akira Shimahara <akira215corp@gmail.com>
   3 Date: Mon, 11 May 2020 22:36:10 +0200
   4 Subject: [PATCH] w1_therm: fix reset_select_slave during discovery
   5
   6 commit c8ad65f6fbfdcb9b620674ef456020eef2bfeb36 upstream.
   7
   8 Fix reset_select_slave issue during devices discovery by the master on
   9 bus. The w1_reset_select_slave() from w1_io.c, which was previously used,
  10 assume that if the slave count is 1 there is only one slave attached on
  11 the bus. This is not always true. For example when discovering devices,
  12 when the first device is discover by the bus master, its slave count is
  13 1, but some other slaves may be on the bus.
  14
  15 In that case instead of adressing command to the attached slave the
  16 master throw a SKIP ROM command so that all slaves attached on the bus
  17 will answer simultenaously causing data collision.
  18
  19 A dedicated reset_select_slave() function is implemented here,
  20 it always perform an adressing to each slave using the MATCH ROM
  21 command.
  22
  23 Signed-off-by: Akira Shimahara <akira215corp@gmail.com>
  24 Link: https://lore.kernel.org/r/20200511203610.409975-1-akira215corp@gmail.com
  25 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  26 ---
  27  drivers/w1/slaves/w1_therm.c | 48 ++++++++++++++++++++++++++++++------
  28  1 file changed, 41 insertions(+), 7 deletions(-)
  29
  30 --- a/drivers/w1/slaves/w1_therm.c
  31 +++ b/drivers/w1/slaves/w1_therm.c
  32 @@ -16,6 +16,7 @@
  33  #include <linux/slab.h>
  34  #include <linux/delay.h>
  35  #include <linux/hwmon.h>
  36 +#include <linux/string.h>
  37
  38  #include <linux/w1.h>
  39
  40 @@ -90,6 +91,24 @@ struct therm_info {
  41         u8 verdict;
  42  };
  43
  44 +/* Hardware Functions declaration */
  45 +
  46 +/**
  47 + * reset_select_slave() - reset and select a slave
  48 + * @sl: the slave to select
  49 + *
  50 + * Resets the bus and select the slave by sending a ROM MATCH cmd
  51 + * w1_reset_select_slave() from w1_io.c could not be used here because
  52 + * it sent a SKIP ROM command if only one device is on the line.
  53 + * At the beginning of the such process, sl->master->slave_count is 1 even if
  54 + * more devices are on the line, causing collision on the line.
  55 + *
  56 + * Context: The w1 master lock must be held.
  57 + *
  58 + * Return: 0 if success, negative kernel error code otherwise.
  59 + */
  60 +static int reset_select_slave(struct w1_slave *sl);
  61 +
  62  /* Sysfs interface declaration */
  63
  64  static ssize_t w1_slave_show(struct device *device,
  65 @@ -301,7 +320,7 @@ static inline int w1_DS18B20_precision(s
  66         while (max_trying--) {
  67                 crc = 0;
  68
  69 -               if (!w1_reset_select_slave(sl)) {
  70 +               if (!reset_select_slave(sl)) {
  71                         int count = 0;
  72
  73                         /* read values to only alter precision bits */
  74 @@ -314,7 +333,7 @@ static inline int w1_DS18B20_precision(s
  75                         if (rom[8] == crc) {
  76                                 rom[4] = (rom[4] & ~mask) | (precision_bits & mask);
  77
  78 -                               if (!w1_reset_select_slave(sl)) {
  79 +                               if (!reset_select_slave(sl)) {
  80                                         w1_write_8(dev, W1_WRITE_SCRATCHPAD);
  81                                         w1_write_8(dev, rom[2]);
  82                                         w1_write_8(dev, rom[3]);
  83 @@ -460,6 +479,21 @@ static void w1_therm_remove_slave(struct
  84
  85  /* Hardware Functions */
  86
  87 +/* Safe version of reset_select_slave - avoid using the one in w_io.c */
  88 +static int reset_select_slave(struct w1_slave *sl)
  89 +{
  90 +       u8 match[9] = { W1_MATCH_ROM, };
  91 +       u64 rn = le64_to_cpu(*((u64 *)&sl->reg_num));
  92 +
  93 +       if (w1_reset_bus(sl->master))
  94 +               return -ENODEV;
  95 +
  96 +       memcpy(&match[1], &rn, 8);
  97 +       w1_write_block(sl->master, match, 9);
  98 +
  99 +       return 0;
 100 +}
 101 +
 102  static ssize_t read_therm(struct device *device,
 103                           struct w1_slave *sl, struct therm_info *info)
 104  {
 105 @@ -487,7 +521,7 @@ static ssize_t read_therm(struct device
 106                 info->verdict = 0;
 107                 info->crc = 0;
 108
 109 -               if (!w1_reset_select_slave(sl)) {
 110 +               if (!reset_select_slave(sl)) {
 111                         int count = 0;
 112                         unsigned int tm = 750;
 113                         unsigned long sleep_rem;
 114 @@ -495,7 +529,7 @@ static ssize_t read_therm(struct device
 115                         w1_write_8(dev, W1_READ_PSUPPLY);
 116                         external_power = w1_read_8(dev);
 117
 118 -                       if (w1_reset_select_slave(sl))
 119 +                       if (reset_select_slave(sl))
 120                                 continue;
 121
 122                         /* 750ms strong pullup (or delay) after the convert */
 123 @@ -525,7 +559,7 @@ static ssize_t read_therm(struct device
 124                                 }
 125                         }
 126
 127 -                       if (!w1_reset_select_slave(sl)) {
 128 +                       if (!reset_select_slave(sl)) {
 129
 130                                 w1_write_8(dev, W1_READ_SCRATCHPAD);
 131                                 count = w1_read_block(dev, info->rom, 9);
 132 @@ -577,7 +611,7 @@ static inline int w1_therm_eeprom(struct
 133         memset(rom, 0, sizeof(rom));
 134
 135         while (max_trying--) {
 136 -               if (!w1_reset_select_slave(sl)) {
 137 +               if (!reset_select_slave(sl)) {
 138                         unsigned int tm = 10;
 139                         unsigned long sleep_rem;
 140
 141 @@ -585,7 +619,7 @@ static inline int w1_therm_eeprom(struct
 142                         w1_write_8(dev, W1_READ_PSUPPLY);
 143                         external_power = w1_read_8(dev);
 144
 145 -                       if (w1_reset_select_slave(sl))
 146 +                       if (reset_select_slave(sl))
 147                                 continue;
 148
 149                         /* 10ms strong pullup/delay after the copy command */