[Linux-stm32] [PATCH v2 1/3] spi: spi-mem: add automatic poll status functions
Andy Shevchenko
andy.shevchenko at gmail.com
Sat May 8 08:07:40 UTC 2021
On Saturday, May 8, 2021, Boris Brezillon <boris.brezillon at collabora.com>
wrote:
> On Fri, 7 May 2021 15:17:54 +0200
> <patrice.chotard at foss.st.com> wrote:
>
> > From: Patrice Chotard <patrice.chotard at foss.st.com>
> >
> > With STM32 QSPI, it is possible to poll the status register of the
> device.
> > This could be done to offload the CPU during an operation (erase or
> > program a SPI NAND for example).
> >
> > spi_mem_poll_status API has been added to handle this feature.
> > This new function take care of the offload/non-offload cases.
> >
> > For the non-offload case, use read_poll_timeout() to poll the status in
> > order to release CPU during this phase.
> >
> > Signed-off-by: Patrice Chotard <patrice.chotard at foss.st.com>
> > Signed-off-by: Christophe Kerello <christophe.kerello at foss.st.com>
> > ---
> > Changes in v2:
> > - Indicates the spi_mem_poll_status() timeout unit
> > - Use 2-byte wide status register
> > - Add spi_mem_supports_op() call in spi_mem_poll_status()
> > - Add completion management in spi_mem_poll_status()
> > - Add offload/non-offload case mangement in spi_mem_poll_status()
> > - Optimize the non-offload case by using read_poll_timeout()
> >
> > drivers/spi/spi-mem.c | 71 +++++++++++++++++++++++++++++++++++++
> > include/linux/spi/spi-mem.h | 10 ++++++
> > 2 files changed, 81 insertions(+)
> >
> > diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> > index 1513553e4080..3f29c604df7d 100644
> > --- a/drivers/spi/spi-mem.c
> > +++ b/drivers/spi/spi-mem.c
> > @@ -6,6 +6,7 @@
> > * Author: Boris Brezillon <boris.brezillon at bootlin.com>
> > */
> > #include <linux/dmaengine.h>
> > +#include <linux/iopoll.h>
> > #include <linux/pm_runtime.h>
> > #include <linux/spi/spi.h>
> > #include <linux/spi/spi-mem.h>
> > @@ -743,6 +744,75 @@ static inline struct spi_mem_driver
> *to_spi_mem_drv(struct device_driver *drv)
> > return container_of(drv, struct spi_mem_driver, spidrv.driver);
> > }
> >
> > +/**
> > + * spi_mem_finalize_op - report completion of spi_mem_op
> > + * @ctlr: the controller reporting completion
> > + *
> > + * Called by SPI drivers using the spi-mem spi_mem_poll_status()
> > + * implementation to notify it that the current spi_mem_op has
> > + * finished.
> > + */
> > +void spi_mem_finalize_op(struct spi_controller *ctlr)
> > +{
> > + complete(&ctlr->xfer_completion);
> > +}
> > +EXPORT_SYMBOL_GPL(spi_mem_finalize_op);
> > +
> > +/**
> > + * spi_mem_poll_status() - Poll memory device status
> > + * @mem: SPI memory device
> > + * @op: the memory operation to execute
> > + * @mask: status bitmask to ckeck
> > + * @match: (status & mask) expected value
> > + * @timeout_ms: timeout in milliseconds
> > + *
> > + * This function send a polling status request to the controller driver
> > + *
> > + * Return: 0 in case of success, -ETIMEDOUT in case of error,
> > + * -EOPNOTSUPP if not supported.
> > + */
> > +int spi_mem_poll_status(struct spi_mem *mem,
> > + const struct spi_mem_op *op,
> > + u16 mask, u16 match, u16 timeout_ms)
> > +{
> > + struct spi_controller *ctlr = mem->spi->controller;
> > + unsigned long ms;
> > + int ret = -EOPNOTSUPP;
> > + int exec_op_ret;
> > + u16 *status;
> > +
> > + if (!spi_mem_supports_op(mem, op))
> > + return ret;
>
> You should only test that in the SW-based polling path. The driver
> ->poll_status() method is expected to check the operation and
> return -EOPNOTSUPP if HW-based polling doesn't work for this op,
> no need to check things twice.
>
> > +
> > + if (ctlr->mem_ops && ctlr->mem_ops->poll_status) {
> > + ret = spi_mem_access_start(mem);
> > + if (ret)
> > + return ret;
> > +
> > + reinit_completion(&ctlr->xfer_completion);
> > +
> > + ret = ctlr->mem_ops->poll_status(mem, op, mask, match,
> > + timeout_ms);
> > +
> > + ms = wait_for_completion_timeout(&ctlr->xfer_completion,
> > +
> msecs_to_jiffies(timeout_ms));
>
> Why do you need to wait here? I'd expect the poll_status to take care
> of this wait.
>
> > +
> > + spi_mem_access_end(mem);
> > + if (!ms)
> > + return -ETIMEDOUT;
> > + } else {
> > + status = (u16 *)op->data.buf.in;
>
> Hm, I don't think it's safe, for 2 reasons:
>
> 1/ op->data.buf.in might be a 1byte buffer, but you're doing a 2byte check
> 2/ data is in big endian in the SPI buffer, which means your check
> won't work on LE architectures.
>
> You really need a dedicated spi_mem_read_status() function that's passed
> an u16 pointer:
>
> int spi_mem_read_status(struct spi_mem *mem,
> const struct spi_mem_op *op,
> u16 *status)
> {
> const u8 *bytes = (u8 *)op->data.buf.in;
> int ret;
>
> ret = spi_mem_exec_op(mem, op);
> if (ret)
> return ret;
>
> if (op->data.nbytes > 1)
> *status = ((u16)bytes[0] << 8) | bytes[1];
Don’t we have get_unaligned_be16() with __be16 type for this? Or
be16_to_cpup() if it’s aligned.
> else
> *status = bytes[0];
>
> return 0;
> }
>
> > + ret = read_poll_timeout(spi_mem_exec_op, exec_op_ret,
> > + ((*status) & mask) == match, 20,
> > + timeout_ms * 1000, false, mem, op);
> > + if (exec_op_ret)
> > + return exec_op_ret;
> > + }
> > +
>
> I would do something like this instead:
>
> int spi_mem_poll_status(struct spi_mem *mem,
> const struct spi_mem_op *op,
> u16 mask, u16 match, u16 timeout_ms)
> {
> struct spi_controller *ctlr = mem->spi->controller;
> int ret = -EOPNOTSUPP;
>
> if (op->data.nbytes < 1 || op->data.nbytes > 2)
> return -EINVAL;
>
> if (ctlr->mem_ops && ctlr->mem_ops->poll_status) {
> ret = spi_mem_access_start(mem);
> if (ret)
> return ret;
>
> ret = ctlr->mem_ops->poll_status(mem, op, mask, match,
> timeout_ms);
>
> spi_mem_access_end(mem);
> }
>
>
> if (ret == -EOPNOTSUPP) {
> u16 status;
> int read_status_ret;
>
> if (!spi_mem_supports_op(mem, op))
> return -EOPNOTSUPP;
>
> ret = read_poll_timeout(spi_mem_read_status, exec_op_ret,
> (read_status_ret || ((status &
> mask) == match), 20,
> timeout_ms * 1000, false, mem, op,
> &status);
>
> if (read_status_ret)
> return read_status_ret;
> }
>
> return ret;
> }
>
> > + return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(spi_mem_poll_status);
> > +
> > static int spi_mem_probe(struct spi_device *spi)
> > {
> > struct spi_mem_driver *memdrv = to_spi_mem_drv(spi->dev.driver);
> > @@ -763,6 +833,7 @@ static int spi_mem_probe(struct spi_device *spi)
> > if (IS_ERR_OR_NULL(mem->name))
> > return PTR_ERR_OR_ZERO(mem->name);
> >
> > + init_completion(&ctlr->xfer_completion);
> > spi_set_drvdata(spi, mem);
> >
> > return memdrv->probe(mem);
> > diff --git a/include/linux/spi/spi-mem.h b/include/linux/spi/spi-mem.h
> > index 2b65c9edc34e..0fbf5d0a3d31 100644
> > --- a/include/linux/spi/spi-mem.h
> > +++ b/include/linux/spi/spi-mem.h
> > @@ -250,6 +250,7 @@ static inline void *spi_mem_get_drvdata(struct
> spi_mem *mem)
> > * the currently mapped area), and the caller of
> > * spi_mem_dirmap_write() is responsible for calling it
> again in
> > * this case.
> > + * @poll_status: poll memory device status
> > *
> > * This interface should be implemented by SPI controllers providing an
> > * high-level interface to execute SPI memory operation, which is
> usually the
> > @@ -274,6 +275,9 @@ struct spi_controller_mem_ops {
> > u64 offs, size_t len, void *buf);
> > ssize_t (*dirmap_write)(struct spi_mem_dirmap_desc *desc,
> > u64 offs, size_t len, const void *buf);
> > + int (*poll_status)(struct spi_mem *mem,
> > + const struct spi_mem_op *op,
> > + u16 mask, u16 match, unsigned long timeout);
> > };
> >
> > /**
> > @@ -369,6 +373,12 @@ devm_spi_mem_dirmap_create(struct device *dev,
> struct spi_mem *mem,
> > void devm_spi_mem_dirmap_destroy(struct device *dev,
> > struct spi_mem_dirmap_desc *desc);
> >
> > +void spi_mem_finalize_op(struct spi_controller *ctlr);
> > +
> > +int spi_mem_poll_status(struct spi_mem *mem,
> > + const struct spi_mem_op *op,
> > + u16 mask, u16 match, u16 timeout);
> > +
> > int spi_mem_driver_register_with_owner(struct spi_mem_driver *drv,
> > struct module *owner);
> >
>
>
--
With Best Regards,
Andy Shevchenko
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