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eeprom: at25: Split reads into chunks and cap write size

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Make use of spi_max_transfer_size to avoid requesting transfers that are
too large for some spi controllers.

Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
Signed-off-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20220524215142.60047-1-eajames@linux.ibm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Brad Bishop 2022-05-24 16:51:42 -05:00 • committed by Greg Kroah-Hartman
parent 1c245358ce
commit 0a35780c75
1 changed files with 55 additions and 42 deletions
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43
drivers/misc/eeprom/at25.c
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@ -79,6 +79,11 @@ static int at25_ee_read(void *priv, unsigned int offset,
{ {
struct at25_data *at25 = priv; struct at25_data *at25 = priv;
char *buf = val; char *buf = val;
size_t max_chunk = spi_max_transfer_size(at25->spi);
size_t num_msgs = DIV_ROUND_UP(count, max_chunk);
size_t nr_bytes = 0;
unsigned int msg_offset;
size_t msg_count;
u8 *cp; u8 *cp;
ssize_t status; ssize_t status;
struct spi_transfer t[2]; struct spi_transfer t[2];
@ -92,11 +97,14 @@ static int at25_ee_read(void *priv, unsigned int offset,
if (unlikely(!count)) if (unlikely(!count))
return -EINVAL; return -EINVAL;
msg_offset = (unsigned int)offset;
msg_count = min(count, max_chunk);
while (num_msgs) {
cp = at25->command; cp = at25->command;
instr = AT25_READ; instr = AT25_READ;
if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR) if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR)
if (offset >= BIT(at25->addrlen * 8)) if (msg_offset >= BIT(at25->addrlen * 8))
instr |= AT25_INSTR_BIT3; instr |= AT25_INSTR_BIT3;
mutex_lock(&at25->lock); mutex_lock(&at25->lock);
@ -106,14 +114,14 @@ static int at25_ee_read(void *priv, unsigned int offset,
/* 8/16/24-bit address is written MSB first */ /* 8/16/24-bit address is written MSB first */
switch (at25->addrlen) { switch (at25->addrlen) {
default: /* case 3 */ default: /* case 3 */
*cp++ = offset >> 16; *cp++ = msg_offset >> 16;
fallthrough; fallthrough;
case 2: case 2:
*cp++ = offset >> 8; *cp++ = msg_offset >> 8;
fallthrough; fallthrough;
case 1: case 1:
case 0: /* can't happen: for better code generation */ case 0: /* can't happen: for better code generation */
*cp++ = offset >> 0; *cp++ = msg_offset >> 0;
} }
spi_message_init(&m); spi_message_init(&m);
@ -123,23 +131,25 @@ static int at25_ee_read(void *priv, unsigned int offset,
t[0].len = at25->addrlen + 1; t[0].len = at25->addrlen + 1;
spi_message_add_tail(&t[0], &m); spi_message_add_tail(&t[0], &m);
t[1].rx_buf = buf; t[1].rx_buf = buf + nr_bytes;
t[1].len = count; t[1].len = msg_count;
spi_message_add_tail(&t[1], &m); spi_message_add_tail(&t[1], &m);
/*
* Read it all at once.
*
* REVISIT that's potentially a problem with large chips, if
* other devices on the bus need to be accessed regularly or
* this chip is clocked very slowly.
*/
status = spi_sync(at25->spi, &m); status = spi_sync(at25->spi, &m);
dev_dbg(&at25->spi->dev, "read %zu bytes at %d --> %zd\n",
count, offset, status);
mutex_unlock(&at25->lock); mutex_unlock(&at25->lock);
if (status)
return status; return status;
--num_msgs;
msg_offset += msg_count;
nr_bytes += msg_count;
}
dev_dbg(&at25->spi->dev, "read %zu bytes at %d\n",
count, offset);
return 0;
} }
/* Read extra registers as ID or serial number */ /* Read extra registers as ID or serial number */
@ -190,6 +200,7 @@ ATTRIBUTE_GROUPS(sernum);
static int at25_ee_write(void *priv, unsigned int off, void *val, size_t count) static int at25_ee_write(void *priv, unsigned int off, void *val, size_t count)
{ {
struct at25_data *at25 = priv; struct at25_data *at25 = priv;
size_t maxsz = spi_max_transfer_size(at25->spi);
const char *buf = val; const char *buf = val;
int status = 0; int status = 0;
unsigned buf_size; unsigned buf_size;
@ -253,6 +264,8 @@ static int at25_ee_write(void *priv, unsigned int off, void *val, size_t count)
segment = buf_size - (offset % buf_size); segment = buf_size - (offset % buf_size);
if (segment > count) if (segment > count)
segment = count; segment = count;
if (segment > maxsz)
segment = maxsz;
memcpy(cp, buf, segment); memcpy(cp, buf, segment);
status = spi_write(at25->spi, bounce, status = spi_write(at25->spi, bounce,
segment + at25->addrlen + 1); segment + at25->addrlen + 1);