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i2c: riic: Add riic_bus_barrier() to check bus availability

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Introduce a new `riic_bus_barrier()` function to verify bus availability
before initiating an I2C transfer. This function enhances the bus
arbitration check by ensuring that the SDA and SCL lines are not held low,
in addition to checking the BBSY flag using `readb_poll_timeout()`.

Previously, only the BBSY flag was checked to determine bus availability.
However, it is possible for the SDA line to remain low even when BBSY = 0.
This new implementation performs an additional check on the SDA and SCL
lines to avoid potential bus contention issues.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
This commit is contained in:
Lad Prabhakar 2025-01-13 12:26:42 +00:00 committed by Wolfram Sang
parent 385bb1c267
commit b31addf2a0
1 changed files with 26 additions and 4 deletions
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30
drivers/i2c/busses/i2c-riic.c
View File

@ -41,6 +41,7 @@
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
@ -51,6 +52,8 @@
#define ICCR1_ICE BIT(7)
#define ICCR1_IICRST BIT(6)
#define ICCR1_SOWP BIT(4)
#define ICCR1_SCLI BIT(1)
#define ICCR1_SDAI BIT(0)
#define ICCR2_BBSY BIT(7)
#define ICCR2_SP BIT(3)
@ -136,6 +139,27 @@ static inline void riic_clear_set_bit(struct riic_dev *riic, u8 clear, u8 set, u
riic_writeb(riic, (riic_readb(riic, reg) & ~clear) | set, reg);
}
static int riic_bus_barrier(struct riic_dev *riic)
{
int ret;
u8 val;
/*
* The SDA line can still be low even when BBSY = 0. Therefore, after checking
* the BBSY flag, also verify that the SDA and SCL lines are not being held low.
*/
ret = readb_poll_timeout(riic->base + riic->info->regs[RIIC_ICCR2], val,
!(val & ICCR2_BBSY), 10, riic->adapter.timeout);
if (ret)
return ret;
if ((riic_readb(riic, RIIC_ICCR1) & (ICCR1_SDAI | ICCR1_SCLI)) !=
(ICCR1_SDAI | ICCR1_SCLI))
return -EBUSY;
return 0;
}
static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
{
struct riic_dev *riic = i2c_get_adapdata(adap);
@ -148,13 +172,11 @@ static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
if (ret)
return ret;
if (riic_readb(riic, RIIC_ICCR2) & ICCR2_BBSY) {
riic->err = -EBUSY;
riic->err = riic_bus_barrier(riic);
if (riic->err)
goto out;
}
reinit_completion(&riic->msg_done);
riic->err = 0;
riic_writeb(riic, 0, RIIC_ICSR2);