From mboxrd@z Thu Jan 1 00:00:00 1970 From: Subject: [PATCH v2 3/6] i2c: at91: Send bus clear command if SCL is down Date: Fri, 3 Jan 2020 09:49:07 +0000 Message-ID: <20200103094821.13185-4-codrin.ciubotariu@microchip.com> References: <20200103094821.13185-1-codrin.ciubotariu@microchip.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20200103094821.13185-1-codrin.ciubotariu@microchip.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: linux-i2c@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: kamel.bouhara@bootlin.com, wsa@the-dreams.de, Nicolas.Ferre@microchip.com, alexandre.belloni@bootlin.com, Ludovic.Desroches@microchip.com, robh@kernel.org, Codrin.Ciubotariu@microchip.com List-Id: linux-i2c@vger.kernel.org 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 --- 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-at= 91-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 =3D { .has_dig_filtr =3D false, .has_adv_dig_filtr =3D false, .has_ana_filtr =3D false, + .has_clear_cmd =3D false, }; =20 static struct at91_twi_pdata at91sam9261_config =3D { @@ -82,6 +83,7 @@ static struct at91_twi_pdata at91sam9261_config =3D { .has_dig_filtr =3D false, .has_adv_dig_filtr =3D false, .has_ana_filtr =3D false, + .has_clear_cmd =3D false, }; =20 static struct at91_twi_pdata at91sam9260_config =3D { @@ -93,6 +95,7 @@ static struct at91_twi_pdata at91sam9260_config =3D { .has_dig_filtr =3D false, .has_adv_dig_filtr =3D false, .has_ana_filtr =3D false, + .has_clear_cmd =3D false, }; =20 static struct at91_twi_pdata at91sam9g20_config =3D { @@ -104,6 +107,7 @@ static struct at91_twi_pdata at91sam9g20_config =3D { .has_dig_filtr =3D false, .has_adv_dig_filtr =3D false, .has_ana_filtr =3D false, + .has_clear_cmd =3D false, }; =20 static struct at91_twi_pdata at91sam9g10_config =3D { @@ -115,6 +119,7 @@ static struct at91_twi_pdata at91sam9g10_config =3D { .has_dig_filtr =3D false, .has_adv_dig_filtr =3D false, .has_ana_filtr =3D false, + .has_clear_cmd =3D false, }; =20 static const struct platform_device_id at91_twi_devtypes[] =3D { @@ -148,6 +153,7 @@ static struct at91_twi_pdata at91sam9x5_config =3D { .has_dig_filtr =3D false, .has_adv_dig_filtr =3D false, .has_ana_filtr =3D false, + .has_clear_cmd =3D false, }; =20 static struct at91_twi_pdata sama5d4_config =3D { @@ -159,6 +165,7 @@ static struct at91_twi_pdata sama5d4_config =3D { .has_dig_filtr =3D true, .has_adv_dig_filtr =3D false, .has_ana_filtr =3D false, + .has_clear_cmd =3D false, }; =20 static struct at91_twi_pdata sama5d2_config =3D { @@ -170,6 +177,7 @@ static struct at91_twi_pdata sama5d2_config =3D { .has_dig_filtr =3D true, .has_adv_dig_filtr =3D true, .has_ana_filtr =3D true, + .has_clear_cmd =3D false, /* due to errata, CLEAR cmd is not working */ }; =20 static struct at91_twi_pdata sam9x60_config =3D { @@ -181,6 +189,7 @@ static struct at91_twi_pdata sam9x60_config =3D { .has_dig_filtr =3D true, .has_adv_dig_filtr =3D true, .has_ana_filtr =3D true, + .has_clear_cmd =3D true, }; =20 static const struct of_device_id atmel_twi_dt_ids[] =3D { 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 *de= v) unsigned long time_left; bool has_unre_flag =3D dev->pdata->has_unre_flag; bool has_alt_cmd =3D dev->pdata->has_alt_cmd; - struct i2c_bus_recovery_info *rinfo =3D &dev->rinfo; + bool has_clear_cmd =3D dev->pdata->has_clear_cmd; =20 /* * 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); } =20 - 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 =3D at91_twi_read(dev, AT91_TWI_ACR); + acr &=3D ~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 =3D &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); + } } =20 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 */ =20 #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 */ =20 #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) =20 #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; }; =20 --=20 2.20.1