Re: spi_mpc8xxx.c: chip select polarity problem
From: Grant Likely <hidden>
Date: 2009-11-25 22:12:19
Also in:
linux-spi
On Wed, Nov 25, 2009 at 1:41 PM, Torsten Fleischer [off-list ref] wrote:
On Wen, Nov 25, 2009 at 01:33:57 Grant Likely wrote:quoted
Thanks. =A0However, there needs to be a proper description of what this patch does to go in the commit header. =A0Can you please write one? Thanks, g.[...] The initialization of the chip selects is removed from the probe() functi=
on of
the spi_mpc8xxx driver, because the driver doesn't know the polarity of t=
he
chip selects of the SPI devices at the time of its initialization. For this reason the initialization of the several chip selects is postpon=
ed
to the point of time when the very first SPI transfer to the associated d=
evice
occurs. Signed-off-by: Torsten Fleischer <redacted>
Ah. I understand what you're doing now. Hmmm. This approach concerns me because it relies on firmware or platform code to get CS gpios set up properly before the driver is probed. Firmware doesn't always get it right, and I prefer to avoid platform specific setups as much as possible. Why can't the CS polarity be encoded into the device tree so the driver *does* have the polarity data at probe time? g.
--- diff -u -r -N linux-2.6.31.6_orig//drivers/spi/spi_mpc8xxx.c linux-2.6.31=
.6/drivers/spi/spi_mpc8xxx.c
quoted hunk ↗ jump to hunk
--- linux-2.6.31.6_orig//drivers/spi/spi_mpc8xxx.c =A0 =A0 =A02009-11-10 =
01:32:31.000000000 +0100
quoted hunk ↗ jump to hunk
+++ linux-2.6.31.6/drivers/spi/spi_mpc8xxx.c =A0 =A02009-11-19 08:15:33.0=
00000000 +0100
quoted hunk ↗ jump to hunk
@@ -114,6 +114,7 @@=A0 =A0 =A0 =A0u32 rx_shift; =A0 =A0 =A0 =A0 =A0 /* RX data reg shift whe=
n in qe mode */
=A0 =A0 =A0 =A0u32 tx_shift; =A0 =A0 =A0 =A0 =A0 /* TX data reg shift whe=
n in qe mode */
=A0 =A0 =A0 =A0u32 hw_mode; =A0 =A0 =A0 =A0 =A0 =A0/* Holds HW mode regis=
ter settings */
quoted hunk ↗ jump to hunk
+ =A0 =A0 =A0 int initialized; =A0}; =A0static inline void mpc8xxx_spi_write_reg(__be32 __iomem *reg, u32 val)@@ -503,15 +504,52 @@=A0 =A0 =A0 =A0return ret; =A0} + + +struct mpc8xxx_spi_probe_info { + =A0 =A0 =A0 struct fsl_spi_platform_data pdata; + =A0 =A0 =A0 int *gpios; + =A0 =A0 =A0 bool *alow_flags; +}; + +static struct mpc8xxx_spi_probe_info * +to_of_pinfo(struct fsl_spi_platform_data *pdata) +{ + =A0 =A0 =A0 return container_of(pdata, struct mpc8xxx_spi_probe_info, p=
data);
+}
+
+static int mpc8xxx_spi_cs_init(struct spi_device *spi)
+{
+ =A0 =A0 =A0 struct device *dev =3D spi->dev.parent;
+ =A0 =A0 =A0 struct mpc8xxx_spi_probe_info *pinfo =3D to_of_pinfo(dev->p=latform_data);
+ =A0 =A0 =A0 u16 cs =3D spi->chip_select; + =A0 =A0 =A0 int gpio =3D pinfo->gpios[cs]; + =A0 =A0 =A0 bool on =3D pinfo->alow_flags[cs] ^ !(spi->mode & SPI_CS_HI=
GH);
+ + =A0 =A0 =A0 return gpio_direction_output(gpio, on); +} + =A0static int mpc8xxx_spi_transfer(struct spi_device *spi, =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0struct spi=
_message *m)
=A0{
=A0 =A0 =A0 =A0struct mpc8xxx_spi *mpc8xxx_spi =3D spi_master_get_devdata=(spi->master);
+ =A0 =A0 =A0 struct spi_mpc8xxx_cs *cs =3D spi->controller_state;
=A0 =A0 =A0 =A0unsigned long flags;
=A0 =A0 =A0 =A0m->actual_length =3D 0;
=A0 =A0 =A0 =A0m->status =3D -EINPROGRESS;
+ =A0 =A0 =A0 if (cs && !cs->initialized) {
+ =A0 =A0 =A0 =A0 =A0 =A0 =A0 int ret;
+
+ =A0 =A0 =A0 =A0 =A0 =A0 =A0 ret =3D mpc8xxx_spi_cs_init(spi);
+ =A0 =A0 =A0 =A0 =A0 =A0 =A0 if (ret) {
+ =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 dev_dbg(&spi->dev, "cs_init=failed: %d\n", ret);
quoted hunk ↗ jump to hunk
+ =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 return ret; + =A0 =A0 =A0 =A0 =A0 =A0 =A0 } + =A0 =A0 =A0 =A0 =A0 =A0 =A0 cs->initialized =3D 1; + =A0 =A0 =A0 } + =A0 =A0 =A0 =A0spin_lock_irqsave(&mpc8xxx_spi->lock, flags); =A0 =A0 =A0 =A0list_add_tail(&m->queue, &mpc8xxx_spi->queue); =A0 =A0 =A0 =A0queue_work(mpc8xxx_spi->workqueue, &mpc8xxx_spi->work);@@ -648,18 +686,6 @@=A0 =A0 =A0 =A0return 0; =A0} -struct mpc8xxx_spi_probe_info { - =A0 =A0 =A0 struct fsl_spi_platform_data pdata; - =A0 =A0 =A0 int *gpios; - =A0 =A0 =A0 bool *alow_flags; -}; - -static struct mpc8xxx_spi_probe_info * -to_of_pinfo(struct fsl_spi_platform_data *pdata) -{ - =A0 =A0 =A0 return container_of(pdata, struct mpc8xxx_spi_probe_info, p=
data);
quoted hunk ↗ jump to hunk
-} - =A0static void mpc8xxx_spi_cs_control(struct spi_device *spi, bool on) =A0{ =A0 =A0 =A0 =A0struct device *dev =3D spi->dev.parent;@@ -720,14 +746,6 @@=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0pinfo->gpios[i] =3D gpio; =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0pinfo->alow_flags[i] =3D flags & OF_GPIO_A=
CTIVE_LOW;
- - =A0 =A0 =A0 =A0 =A0 =A0 =A0 ret =3D gpio_direction_output(pinfo->gpios[=
i],
- =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
=A0 =A0 =A0 pinfo->alow_flags[i]);
- =A0 =A0 =A0 =A0 =A0 =A0 =A0 if (ret) {
- =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 dev_err(dev, "can't set out=put direction for gpio "
- =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "#%d: %d\n"=
, i, ret);
- =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 goto err_loop; - =A0 =A0 =A0 =A0 =A0 =A0 =A0 } =A0 =A0 =A0 =A0} =A0 =A0 =A0 =A0pdata->max_chipselect =3D ngpios;
--=20 Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd.