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Message-ID: <d2fb2414-5c7f-3bc0-caf5-8927e6a2ccee@microchip.com>
Date: Thu, 9 Jan 2020 10:58:22 +0000
From: <Codrin.Ciubotariu@...rochip.com>
To: <linux-i2c@...r.kernel.org>, <devicetree@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <kamel.bouhara@...tlin.com>,
<wsa@...-dreams.de>, <Nicolas.Ferre@...rochip.com>,
<alexandre.belloni@...tlin.com>, <robh@...nel.org>
Subject: Re: [PATCH v2 3/6] i2c: at91: Send bus clear command if SCL is down
On 09.01.2020 09:47, Ludovic Desroches wrote:
> On Fri, Jan 03, 2020 at 09:49:07AM +0000, Codrin Ciubotariu - M19940 wrote:
>> After a transfer timeout, some faulty I2C slave devices might hold down
>> the SCL pin. We can generate a bus clear command, hoping that the slave
>> might release the pins.
>>
>> Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>
>
> This patch may conflict with another one removing the explicit set to
> false.
Yes, Eugen's patches got accepted in the meantime. I will rebase and
adapt to the new style.
>
>> ---
>>
>> Changes in v2:
>> - use CLEAR command only if SDA is down; update patch subject to
>> reflect this;
>> - CLEAR command is no longer used for sama5d2, only sam9x60;
>>
>> drivers/i2c/busses/i2c-at91-core.c | 9 ++++++++
>> drivers/i2c/busses/i2c-at91-master.c | 32 +++++++++++++++++++++++-----
>> drivers/i2c/busses/i2c-at91.h | 7 +++++-
>> 3 files changed, 42 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-at91-core.c b/drivers/i2c/busses/i2c-at91-core.c
>> index e13af4874976..128eafc05adb 100644
>> --- a/drivers/i2c/busses/i2c-at91-core.c
>> +++ b/drivers/i2c/busses/i2c-at91-core.c
>> @@ -71,6 +71,7 @@ static struct at91_twi_pdata at91rm9200_config = {
>> .has_dig_filtr = false,
>> .has_adv_dig_filtr = false,
>> .has_ana_filtr = false,
>> + .has_clear_cmd = false,
>> };
>>
>> static struct at91_twi_pdata at91sam9261_config = {
>> @@ -82,6 +83,7 @@ static struct at91_twi_pdata at91sam9261_config = {
>> .has_dig_filtr = false,
>> .has_adv_dig_filtr = false,
>> .has_ana_filtr = false,
>> + .has_clear_cmd = false,
>> };
>>
>> static struct at91_twi_pdata at91sam9260_config = {
>> @@ -93,6 +95,7 @@ static struct at91_twi_pdata at91sam9260_config = {
>> .has_dig_filtr = false,
>> .has_adv_dig_filtr = false,
>> .has_ana_filtr = false,
>> + .has_clear_cmd = false,
>> };
>>
>> static struct at91_twi_pdata at91sam9g20_config = {
>> @@ -104,6 +107,7 @@ static struct at91_twi_pdata at91sam9g20_config = {
>> .has_dig_filtr = false,
>> .has_adv_dig_filtr = false,
>> .has_ana_filtr = false,
>> + .has_clear_cmd = false,
>> };
>>
>> static struct at91_twi_pdata at91sam9g10_config = {
>> @@ -115,6 +119,7 @@ static struct at91_twi_pdata at91sam9g10_config = {
>> .has_dig_filtr = false,
>> .has_adv_dig_filtr = false,
>> .has_ana_filtr = false,
>> + .has_clear_cmd = false,
>> };
>>
>> static const struct platform_device_id at91_twi_devtypes[] = {
>> @@ -148,6 +153,7 @@ static struct at91_twi_pdata at91sam9x5_config = {
>> .has_dig_filtr = false,
>> .has_adv_dig_filtr = false,
>> .has_ana_filtr = false,
>> + .has_clear_cmd = false,
>> };
>>
>> static struct at91_twi_pdata sama5d4_config = {
>> @@ -159,6 +165,7 @@ static struct at91_twi_pdata sama5d4_config = {
>> .has_dig_filtr = true,
>> .has_adv_dig_filtr = false,
>> .has_ana_filtr = false,
>> + .has_clear_cmd = false,
>> };
>>
>> static struct at91_twi_pdata sama5d2_config = {
>> @@ -170,6 +177,7 @@ static struct at91_twi_pdata sama5d2_config = {
>> .has_dig_filtr = true,
>> .has_adv_dig_filtr = true,
>> .has_ana_filtr = true,
>> + .has_clear_cmd = false, /* due to errata, CLEAR cmd is not working */
>
> In this case it's probably worth keeping it.
Yes, I also think it's useful to let this one.
Thanks and best regards,
Codrin
>
> Ludovic
>
>> };
>>
>> static struct at91_twi_pdata sam9x60_config = {
>> @@ -181,6 +189,7 @@ static struct at91_twi_pdata sam9x60_config = {
>> .has_dig_filtr = true,
>> .has_adv_dig_filtr = true,
>> .has_ana_filtr = true,
>> + .has_clear_cmd = true,
>> };
>>
>> static const struct of_device_id atmel_twi_dt_ids[] = {
>> diff --git a/drivers/i2c/busses/i2c-at91-master.c b/drivers/i2c/busses/i2c-at91-master.c
>> index c55e8ff35201..8c4f20317847 100644
>> --- a/drivers/i2c/busses/i2c-at91-master.c
>> +++ b/drivers/i2c/busses/i2c-at91-master.c
>> @@ -480,7 +480,7 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
>> unsigned long time_left;
>> bool has_unre_flag = dev->pdata->has_unre_flag;
>> bool has_alt_cmd = dev->pdata->has_alt_cmd;
>> - struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
>> + bool has_clear_cmd = dev->pdata->has_clear_cmd;
>>
>> /*
>> * WARNING: the TXCOMP bit in the Status Register is NOT a clear on
>> @@ -641,10 +641,32 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
>> AT91_TWI_THRCLR | AT91_TWI_LOCKCLR);
>> }
>>
>> - if (rinfo->get_sda && !(rinfo->get_sda(&dev->adapter))) {
>> - dev_dbg(dev->dev,
>> - "SDA is down; clear bus using gpio\n");
>> - i2c_recover_bus(&dev->adapter);
>> + /*
>> + * some faulty I2C slave devices might hold SDA down;
>> + * we can send a bus clear command, hoping that the pins will be
>> + * released
>> + */
>> + if (has_clear_cmd) {
>> + if (!(dev->transfer_status & AT91_TWI_SDA)) {
>> + dev_dbg(dev->dev,
>> + "SDA is down; sending bus clear command\n");
>> + if (dev->use_alt_cmd) {
>> + unsigned int acr;
>> +
>> + acr = at91_twi_read(dev, AT91_TWI_ACR);
>> + acr &= ~AT91_TWI_ACR_DATAL_MASK;
>> + at91_twi_write(dev, AT91_TWI_ACR, acr);
>> + }
>> + at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_CLEAR);
>> + }
>> + } else {
>> + struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
>> +
>> + if (rinfo->get_sda && !(rinfo->get_sda(&dev->adapter))) {
>> + dev_dbg(dev->dev,
>> + "SDA is down; clear bus using gpio\n");
>> + i2c_recover_bus(&dev->adapter);
>> + }
>> }
>>
>> return ret;
>> diff --git a/drivers/i2c/busses/i2c-at91.h b/drivers/i2c/busses/i2c-at91.h
>> index eb335b71e775..80f77d523346 100644
>> --- a/drivers/i2c/busses/i2c-at91.h
>> +++ b/drivers/i2c/busses/i2c-at91.h
>> @@ -36,6 +36,7 @@
>> #define AT91_TWI_SVDIS BIT(5) /* Slave Transfer Disable */
>> #define AT91_TWI_QUICK BIT(6) /* SMBus quick command */
>> #define AT91_TWI_SWRST BIT(7) /* Software Reset */
>> +#define AT91_TWI_CLEAR BIT(15) /* Bus clear command */
>> #define AT91_TWI_ACMEN BIT(16) /* Alternative Command Mode Enable */
>> #define AT91_TWI_ACMDIS BIT(17) /* Alternative Command Mode Disable */
>> #define AT91_TWI_THRCLR BIT(24) /* Transmit Holding Register Clear */
>> @@ -69,6 +70,8 @@
>> #define AT91_TWI_NACK BIT(8) /* Not Acknowledged */
>> #define AT91_TWI_EOSACC BIT(11) /* End Of Slave Access */
>> #define AT91_TWI_LOCK BIT(23) /* TWI Lock due to Frame Errors */
>> +#define AT91_TWI_SCL BIT(24) /* TWI SCL status */
>> +#define AT91_TWI_SDA BIT(25) /* TWI SDA status */
>>
>> #define AT91_TWI_INT_MASK \
>> (AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY | AT91_TWI_NACK \
>> @@ -81,7 +84,8 @@
>> #define AT91_TWI_THR 0x0034 /* Transmit Holding Register */
>>
>> #define AT91_TWI_ACR 0x0040 /* Alternative Command Register */
>> -#define AT91_TWI_ACR_DATAL(len) ((len) & 0xff)
>> +#define AT91_TWI_ACR_DATAL_MASK GENMASK(15, 0)
>> +#define AT91_TWI_ACR_DATAL(len) ((len) & AT91_TWI_ACR_DATAL_MASK)
>> #define AT91_TWI_ACR_DIR BIT(8)
>>
>> #define AT91_TWI_FILTR 0x0044
>> @@ -118,6 +122,7 @@ struct at91_twi_pdata {
>> bool has_dig_filtr;
>> bool has_adv_dig_filtr;
>> bool has_ana_filtr;
>> + bool has_clear_cmd;
>> struct at_dma_slave dma_slave;
>> };
>>
>> --
>> 2.20.1
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