NAK: [PATCH v2 1/1][SRU][Bionic] UBUNTU: SAUCE: at24: add 16-bit width registers support
AceLan Kao
acelan.kao at canonical.com
Fri May 15 03:46:17 UTC 2020
I'm willing to fix this patch and I hope we can start to review
patches earlier and
not NACK it at last moment. This leads to projects don't have a
working kernel for around 2 months.
1. I didn't call this is a port of upstream patch. I wrote this in the patch
> This commit is derivated from below commit, and then modified and provided
> by customer
> https://patchwork.ozlabs.org/patch/545292/
And say
> I migrate the commit to latest kernel and finally get it merged.
2. Okay, I just sent out an email to ask for the permission to add
author's signed off
Kamal Mostafa <kamal at canonical.com> 於 2020年5月15日 週五 上午12:18寫道：
>
> Hi AceLan-
>
> After a discussion with Stefan and Kleber, we are not comfortable with
> this version for bionic:
>
> 1. The significant difference from the upstream-accepted focal version
> is confusing. (Perhaps it would be better to just develop a separate
> UBUNTU SAUCE patch for bionic, instead of calling this a "port" of the
> upstream patch?)
>
> 2. We'd like to have the author's Signed-off-by. Please contact the
> author and ask for it.
>
> Thanks for your patience!
>
> -Kamal
>
> On Thu, May 14, 2020 at 06:38:34PM +0800, AceLan Kao wrote:
> > From: Pieri <pierluigi.driusso at eurotech.com>
> >
> > BugLink: https://bugs.launchpad.net/bugs/1876699
> >
> > This allows to access EEPROM with 16-bit width of registers via i2c SMBus
> > block functions.
> >
> > This commit is derivated from below commit, and then modified and provided
> > by customer
> > https://patchwork.ozlabs.org/patch/545292/
> > Unfortunately, this commit didn't get merged into mainline in the end.
> >
> > From the discussion in the patch thread and another lengthy discussion[1],
> > it looks like the maintainer is convinced to accept this patch[2].
> > But it turns out that there is a new idea to test[3] and the result is
> > not good, and the origin patch has been forgotten and didn't get merged
> > in the end.
> >
> > In the discussion, the implementation to support access 16-bit address data
> > is not safe. The multi-command sequence of the read function is not safe
> > and may read the wrong data from other address if other commands are sent
> > in-between the SMBus commands in the read function.
> >
> > 1. https://lkml.org/lkml/2015/2/4/436
> > 2. https://lkml.org/lkml/2015/3/25/619
> > 3. https://lkml.org/lkml/2015/3/27/99
> >
> > Signed-off-by: AceLan Kao <acelan.kao at canonical.com>
> > ---
> > drivers/misc/eeprom/Kconfig | 5 +-
> > drivers/misc/eeprom/at24.c | 139 +++++++++++++++++++++++++++++++-----
> > 2 files changed, 127 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/misc/eeprom/Kconfig b/drivers/misc/eeprom/Kconfig
> > index 3f93e4564cab9..27b0e8ee04926 100644
> > --- a/drivers/misc/eeprom/Kconfig
> > +++ b/drivers/misc/eeprom/Kconfig
> > @@ -23,7 +23,10 @@ config EEPROM_AT24
> >
> > If you use this with an SMBus adapter instead of an I2C adapter,
> > full functionality is not available. Only smaller devices are
> > - supported (24c16 and below, max 4 kByte).
> > + supported via block reads (24c16 and below, max 4 kByte).
> > + Larger devices that use 16-bit addresses will only work with
> > + individual byte reads, which is very slow in general and is unsafe
> > + in multi-master SMBus topologies.
> >
> > This driver can also be built as a module. If so, the module
> > will be called at24.
> > diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> > index 7554b001b502f..614b5b2c5bbd9 100644
> > --- a/drivers/misc/eeprom/at24.c
> > +++ b/drivers/misc/eeprom/at24.c
> > @@ -3,6 +3,7 @@
> > *
> > * Copyright (C) 2005-2007 David Brownell
> > * Copyright (C) 2008 Wolfram Sang, Pengutronix
> > + * Copyright (C) 2015 Extreme Engineering Solutions, Inc.
> > *
> > * 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
> > @@ -52,7 +53,7 @@
> > * Other than binding model, current differences from "eeprom" driver are
> > * that this one handles write access and isn't restricted to 24c02 devices.
> > * It also handles larger devices (32 kbit and up) with two-byte addresses,
> > - * which won't work on pure SMBus systems.
> > + * which don't work without risks on pure SMBus systems.
> > */
> >
> > struct at24_data {
> > @@ -246,6 +247,88 @@ MODULE_DEVICE_TABLE(acpi, at24_acpi_ids);
> > * one "eeprom" file not four, but larger reads would fail when
> > * they crossed certain pages.
> > */
> > +
> > +/*
> > + * Write a byte to an AT24 device using SMBus cycles.
> > + */
> > +static inline s32 at24_smbus_write_byte_data(struct at24_data *at24,
> > + struct i2c_client *client, u16 offset, u8 value)
> > +{
> > + if (!(at24->chip.flags & AT24_FLAG_ADDR16))
> > + return i2c_smbus_write_byte_data(client, offset, value);
> > +
> > + /*
> > + * Emulate I2C multi-byte write by using SMBus "write word"
> > + * cycle. We split up the 16-bit offset among the "command"
> > + * byte and the first data byte.
> > + */
> > + return i2c_smbus_write_word_data(client, offset >> 8,
> > + (value << 8) | (offset & 0xff));
> > +}
> > +
> > +/*
> > + * Write block data to an AT24 device using SMBus cycles.
> > + */
> > +static inline s32 at24_smbus_write_i2c_block_data(struct at24_data *at24,
> > + const struct i2c_client *client, u16 off, u8 len, const u8 *vals)
> > +{
> > + s32 res;
> > +
> > + if (!(at24->chip.flags & AT24_FLAG_ADDR16))
> > + return i2c_smbus_write_i2c_block_data(client, off, len, vals);
> > +
> > + /* Insert extra address byte into data stream */
> > + at24->writebuf[0] = off & 0xff;
> > + memcpy(&at24->writebuf[1], vals, len);
> > +
> > + res = i2c_smbus_write_i2c_block_data(client, off >> 8, len + 1,
> > + at24->writebuf);
> > +
> > + return res;
> > +}
> > +
> > +/*
> > + * Read block data from an AT24 device using SMBus cycles.
> > + */
> > +static inline s32 at24_smbus_read_block_data(struct at24_data *at24,
> > + const struct i2c_client *client, u16 off, u8 len, u8 *vals)
> > +{
> > + int count;
> > + s32 res;
> > +
> > + if (!(at24->chip.flags & AT24_FLAG_ADDR16))
> > + return i2c_smbus_read_i2c_block_data_or_emulated(client, off,
> > + len, vals);
> > +
> > + /*
> > + * Emulate I2C multi-byte read by using SMBus "write byte" and
> > + * "receive byte". This is slightly unsafe since there is an
> > + * additional STOP involved, which exposes the SMBus and (this
> > + * device!) to takeover by another bus master. However, it's the
> > + * only way to work on SMBus-only controllers when talking to
> > + * EEPROMs with multi-byte addresses.
> > + */
> > +
> > + /* Address "dummy" write */
> > + res = i2c_smbus_write_byte_data(client, off >> 8, off & 0xff);
> > + if (res < 0)
> > + return res;
> > +
> > + count = 0;
> > + do {
> > + /* Current Address Read */
> > + res = i2c_smbus_read_byte(client);
> > + if (res < 0)
> > + break;
> > +
> > + *(vals++) = res;
> > + count++;
> > + len--;
> > + } while (len > 0);
> > +
> > + return count;
> > +}
> > +
> > static struct i2c_client *at24_translate_offset(struct at24_data *at24,
> > unsigned int *offset)
> > {
> > @@ -286,10 +369,8 @@ static ssize_t at24_eeprom_read_smbus(struct at24_data *at24, char *buf,
> > */
> > read_time = jiffies;
> >
> > - status = i2c_smbus_read_i2c_block_data_or_emulated(client,
> > - offset,
> > - count, buf);
> > -
> > + status = at24_smbus_read_block_data(at24, client,
> > + offset, count, buf);
> > dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
> > count, offset, status, jiffies);
> >
> > @@ -508,8 +589,8 @@ static ssize_t at24_eeprom_write_smbus_block(struct at24_data *at24,
> > */
> > write_time = jiffies;
> >
> > - status = i2c_smbus_write_i2c_block_data(client,
> > - offset, count, buf);
> > + status = at24_smbus_write_i2c_block_data(at24,
> > + client, offset, count, buf);
> > if (status == 0)
> > status = count;
> >
> > @@ -543,7 +624,8 @@ static ssize_t at24_eeprom_write_smbus_byte(struct at24_data *at24,
> > */
> > write_time = jiffies;
> >
> > - status = i2c_smbus_write_byte_data(client, offset, buf[0]);
> > + status = at24_smbus_write_byte_data(at24, client, offset,
> > + buf[0]);
> > if (status == 0)
> > status = count;
> >
> > @@ -810,13 +892,32 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
> >
> > /* Use I2C operations unless we're stuck with SMBus extensions. */
> > if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
> > - if (chip.flags & AT24_FLAG_ADDR16)
> > - return -EPFNOSUPPORT;
> > -
> > - if (i2c_check_functionality(client->adapter,
> > + if ((chip.flags & AT24_FLAG_ADDR16) &&
> > + i2c_check_functionality(client->adapter,
> > + I2C_FUNC_SMBUS_READ_BYTE |
> > + I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) {
> > + /*
> > + * We need SMBUS_WRITE_BYTE_DATA and SMBUS_READ_BYTE to
> > + * implement byte reads for 16-bit address devices.
> > + * This will be slow, but better than nothing (e.g.
> > + * read @ 3.6 KiB/s). It is also unsafe in a multi-
> > + * master topology.
> > + */
> > + use_smbus = I2C_SMBUS_BYTE_DATA;
> > + } else if (i2c_check_functionality(client->adapter,
> > I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
> > use_smbus = I2C_SMBUS_I2C_BLOCK_DATA;
> > - } else if (i2c_check_functionality(client->adapter,
> > + } else if ((chip.flags & AT24_FLAG_ADDR16) &&
> > + i2c_check_functionality(client->adapter,
> > + I2C_FUNC_SMBUS_WRITE_WORD_DATA)) {
> > + /*
> > + * We need SMBUS_WRITE_WORD_DATA to implement
> > + * byte writes for 16-bit address devices.
> > + */
> > + use_smbus_write = I2C_SMBUS_BYTE_DATA;
> > + chip.page_size = 1;
> > + } else if (!(chip.flags & AT24_FLAG_ADDR16) &&
> > + i2c_check_functionality(client->adapter,
> > I2C_FUNC_SMBUS_READ_WORD_DATA)) {
> > use_smbus = I2C_SMBUS_WORD_DATA;
> > } else if (i2c_check_functionality(client->adapter,
> > @@ -836,6 +937,9 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
> > }
> > }
> >
> > + if (strcmp(client->name, "24c256") == 0)
> > + chip.page_size = 64;
> > +
> > if (chip.flags & AT24_FLAG_TAKE8ADDR)
> > num_addresses = 8;
> > else
> > @@ -881,12 +985,15 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
> > if (writable) {
> > if (!use_smbus || use_smbus_write) {
> >
> > - unsigned write_max = chip.page_size;
> > + unsigned int write_max = chip.page_size;
> > + unsigned int smbus_max = (chip.flags & AT24_FLAG_ADDR16) ?
> > + I2C_SMBUS_BLOCK_MAX - 1 :
> > + I2C_SMBUS_BLOCK_MAX;
> >
> > if (write_max > io_limit)
> > write_max = io_limit;
> > - if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
> > - write_max = I2C_SMBUS_BLOCK_MAX;
> > + if (use_smbus && write_max > smbus_max)
> > + write_max = smbus_max;
> > at24->write_max = write_max;
> >
> > /* buffer (data + address at the beginning) */
> > --
> > 2.25.1
> >
> >
> > --
> > kernel-team mailing list
> > kernel-team at lists.ubuntu.com
> > https://lists.ubuntu.com/mailman/listinfo/kernel-team
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