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Date: Wed, 8 Apr 2015 21:32:09 +0200
From: Jonas Gorski <jogo@...nwrt.org>
To: Jonathan Richardson <jonathar@...adcom.com>
Cc: Mark Brown <broonie@...nel.org>, Dmitry Torokhov <dtor@...gle.com>,
Anatol Pomazau <anatol@...gle.com>,
Scott Branden <sbranden@...adcom.com>,
Rob Herring <robh+dt@...nel.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
linux-spi@...r.kernel.org,
bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
Rafal Milecki <zajec5@...il.com>
Subject: Re: [PATCH v2 5/5] spi: bcm-mspi: Add support to set serial baud
clock rate
Hi,
On Wed, Apr 8, 2015 at 8:04 PM, Jonathan Richardson
<jonathar@...adcom.com> wrote:
> The driver wasn't setting the SPBR (serial clock baud rate) which caused
> it to run at the slowest speed possible. The driver now calculates the
> SPBR based on the reference clock frequency resulting in much faster
> SPI transfers.
>
> Signed-off-by: Jonathan Richardson <jonathar@...adcom.com>
> ---
> drivers/spi/spi-bcm-mspi.c | 50 ++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 50 insertions(+)
>
> diff --git a/drivers/spi/spi-bcm-mspi.c b/drivers/spi/spi-bcm-mspi.c
> index 32bb1f0..9320de9 100644
> --- a/drivers/spi/spi-bcm-mspi.c
> +++ b/drivers/spi/spi-bcm-mspi.c
> @@ -18,10 +18,15 @@
> #include <linux/bcma/bcma.h>
> #include <linux/spi/spi.h>
> #include <linux/of.h>
> +#include <linux/clk.h>
>
> #include "spi-bcm-mspi.h"
>
> #define BCM_MSPI_MAX_SPI_BAUD 13500000 /* 216 MHz? */
> +#define SPBR_MIN 8U
> +#define SPBR_MAX 255U
> +#define MSPI_SPCR0_LSB_OFFSET 0x200
> +#define MSPI_SPCR0_LSB_SHIFT 0
>
> /* The longest observed required wait was 19 ms */
> #define BCM_MSPI_SPE_TIMEOUT_MS 80
> @@ -33,7 +38,9 @@ struct bcm_mspi {
>
> void __iomem *base;
> struct spi_master *master;
> + struct clk *clk;
> size_t read_offset;
> + u32 spbr;
>
> void (*mspi_write)(struct bcm_mspi *mspi, u16 offset, u32 value);
> u32 (*mspi_read)(struct bcm_mspi *mspi, u16 offset);
> @@ -45,6 +52,15 @@ static inline unsigned int bcm_mspi_calc_timeout(size_t len)
> return (len * 9000 / BCM_MSPI_MAX_SPI_BAUD * 110 / 100) + 1;
> }
>
> +static void bcm_mspi_hw_init(struct bcm_mspi *mspi)
> +{
> + /* Set SPBR (serial clock baud rate). */
> + if (mspi->spbr) {
> + mspi->mspi_write(mspi, MSPI_SPCR0_LSB_OFFSET,
> + mspi->spbr << MSPI_SPCR0_LSB_SHIFT);
> + }
> +}
> +
> static int bcm_mspi_wait(struct bcm_mspi *mspi, unsigned int timeout_ms)
> {
> unsigned long deadline;
> @@ -222,6 +238,7 @@ static struct bcm_mspi *bcm_mspi_init(struct device *dev)
> {
> struct bcm_mspi *data;
> struct spi_master *master;
> + u32 desired_rate;
>
> master = spi_alloc_master(dev, sizeof(*data));
> if (!master) {
> @@ -236,6 +253,33 @@ static struct bcm_mspi *bcm_mspi_init(struct device *dev)
> master->dev.of_node = dev->of_node;
> master->transfer_one = bcm_mspi_transfer_one;
>
> + /*
> + * Enable clock if provided. The frequency can be changed by setting
> + * SPBR (serial clock baud rate) based on the desired 'clock-frequency'.
> + *
> + * Baud rate is calculated as: mspi_clk / (2 * SPBR) where SPBR is a
> + * value between 1-255. If not set then it is left at the h/w default.
> + */
> + data->clk = devm_clk_get(dev, "mspi_clk");
> + if (!IS_ERR(data->clk)) {
> + int ret = clk_prepare_enable(data->clk);
You need to disable_unprepare the clock on removal, I don't see you doing that.
> +
> + if (ret < 0) {
> + dev_err(dev, "failed to enable clock: %d\n", ret);
> + return 0;
> + }
> +
> + /* Calculate SPBR if clock-frequency provided. */
> + if (of_property_read_u32(dev->of_node, "clock-frequency",
> + &desired_rate) >= 0) {
> + u32 spbr = clk_get_rate(data->clk) / (2 * desired_rate);
> +
> + if (spbr > 0)
> + data->spbr = clamp_val(spbr, SPBR_MIN,
> + SPBR_MAX);
> + }
> + }
> +
> return data;
> }
>
> @@ -287,6 +331,9 @@ static int bcm_mspi_probe(struct platform_device *pdev)
> data->mspi_write = bcm_mspi_write;
> platform_set_drvdata(pdev, data);
>
> + /* Initialize SPI controller. */
> + bcm_mspi_hw_init(data);
> +
> err = devm_spi_register_master(dev, data->master);
> if (err)
> goto out;
> @@ -362,6 +409,9 @@ static int bcm_mspi_bcma_probe(struct bcma_device *core)
>
> bcma_set_drvdata(core, data);
>
> + /* Initialize SPI controller. */
> + bcm_mspi_hw_init(data);
> +
> err = devm_spi_register_master(&core->dev, data->master);
> if (err) {
> spi_master_put(data->master);
> --
Regards
Jonas
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