Re: [PATCH v3 7/7] mfd: cros_ec: spi: Add delay for asserting CS

Lee Jones
2015-05-27T09:14:55Z

On Fri, 22 May 2015, Javier Martinez Canillas wrote:

> From: Alexandru M Stan <amstan@chromium.org>
>
> Some ECs need a little time for waking up before they can accept
> SPI data at a high speed. This is configurable via a DT property
> "google,cros-ec-spi-pre-delay".
>
> If this property isn't set, then no delay will be added. However,
> if set it will cause a delay equal to the value passed to it to
> be inserted at the beginning of a transaction.
>
> Signed-off-by: Alexandru M Stan <amstan@chromium.org>
> Reviewed-by: Doug Anderson <dianders@chromium.org>
> Signed-off-by: Chris Zhong <zyw@rock-chips.com>
> Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
> ---
>
> Changes since v2: None
>
> Changes since v1: None, new patch
> ---
> Documentation/devicetree/bindings/mfd/cros-ec.txt | 4 ++++
> drivers/mfd/cros_ec_spi.c | 21 +++++++++++++++++++--

These two should be separate patches.

> 2 files changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/mfd/cros-ec.txt b/Documentation/devicetree/bindings/mfd/cros-ec.txt
> index 8009c3d87f33..1777916e9e28 100644
> --- a/Documentation/devicetree/bindings/mfd/cros-ec.txt
> +++ b/Documentation/devicetree/bindings/mfd/cros-ec.txt
> @@ -18,6 +18,10 @@ Required properties (SPI):
> - reg: SPI chip select
>
> Optional properties (SPI):
> +- google,cros-ec-spi-pre-delay: Some implementations of the EC need a little
> + time to wake up from sleep before they can receive SPI transfers at a high
> + clock rate. This property specifies the delay, in usecs, between the
> + assertion of the CS to the start of the first clock pulse.
> - google,cros-ec-spi-msg-delay: Some implementations of the EC require some
> additional processing time in order to accept new transactions. If the delay
> between transactions is not long enough the EC may not be able to respond

When re-submitting as seperate patches:
Acked-by: Lee Jones <lee.jones@linaro.org>

> diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
> index faba03e2f1ef..16f228dc243f 100644
> --- a/drivers/mfd/cros_ec_spi.c
> +++ b/drivers/mfd/cros_ec_spi.c
> @@ -71,12 +71,15 @@
> * @spi: SPI device we are connected to
> * @last_transfer_ns: time that we last finished a transfer, or 0 if there
> * if no record
> + * @start_of_msg_delay: used to set the delay_usecs on the spi_transfer that
> + * is sent when we want to turn on CS at the start of a transaction.
> * @end_of_msg_delay: used to set the delay_usecs on the spi_transfer that
> * is sent when we want to turn off CS at the end of a transaction.
> */
> struct cros_ec_spi {
> struct spi_device *spi;
> s64 last_transfer_ns;
> + unsigned int start_of_msg_delay;
> unsigned int end_of_msg_delay;
> };
>
> @@ -366,7 +369,7 @@ static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
> struct ec_host_request *request;
> struct ec_host_response *response;
> struct cros_ec_spi *ec_spi = ec_dev->priv;
> - struct spi_transfer trans;
> + struct spi_transfer trans, trans_delay;
> struct spi_message msg;
> int i, len;
> u8 *ptr;
> @@ -393,13 +396,23 @@ static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
> goto exit;
> }
>
> + /*
> + * Leave a gap between CS assertion and clocking of data to allow the
> + * EC time to wakeup.
> + */
> + spi_message_init(&msg);
> + if (ec_spi->start_of_msg_delay) {
> + memset(&trans_delay, 0, sizeof(trans_delay));
> + trans_delay.delay_usecs = ec_spi->start_of_msg_delay;
> + spi_message_add_tail(&trans_delay, &msg);
> + }
> +
> /* Transmit phase - send our message */
> memset(&trans, 0, sizeof(trans));
> trans.tx_buf = ec_dev->dout;
> trans.rx_buf = rx_buf;
> trans.len = len;
> trans.cs_change = 1;
> - spi_message_init(&msg);
> spi_message_add_tail(&trans, &msg);
> ret = spi_sync(ec_spi->spi, &msg);
>
> @@ -602,6 +615,10 @@ static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev)
> u32 val;
> int ret;
>
> + ret = of_property_read_u32(np, "google,cros-ec-spi-pre-delay", &val);
> + if (!ret)
> + ec_spi->start_of_msg_delay = val;
> +
> ret = of_property_read_u32(np, "google,cros-ec-spi-msg-delay", &val);
> if (!ret)
> ec_spi->end_of_msg_delay = val;

And for this patch:
Acked-by: Lee Jones <lee.jones@linaro.org>

--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
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