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Date: Thu, 29 Jan 2015 14:05:41 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Cc: Kukjin Kim <kgene@...nel.org>,
Doug Anderson <dianders@...omium.org>,
Olof Johansson <olof@...om.net>,
Arend van Spriel <arend@...adcom.com>,
Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
linux-mmc <linux-mmc@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/6] mmc: pwrseq_simple: Add optional reference clock support
On 28 January 2015 at 19:15, Javier Martinez Canillas
<javier.martinez@...labora.co.uk> wrote:
> Some WLAN chips attached to a SDIO interface, need a reference clock.
>
> Since this is very common, extend the prseq_simple driver to support
> an optional clock that is enabled prior the card power up procedure.
>
> Note: the external clock is optional. Thus an error is not returned
> if the clock is not found.
>
> Signed-off-by: Javier Martinez Canillas <javier.martinez@...labora.co.uk>
> ---
>
> Changes since v1:
> - Rebase on top of latest changes.
> - Use IS_ERR() instead of checking for NULL to see if the clock exists.
> ---
> drivers/mmc/core/pwrseq_simple.c | 34 ++++++++++++++++++++++++++++++++--
> 1 file changed, 32 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/core/pwrseq_simple.c b/drivers/mmc/core/pwrseq_simple.c
> index e53d3c7e059c..5e34c77efa5e 100644
> --- a/drivers/mmc/core/pwrseq_simple.c
> +++ b/drivers/mmc/core/pwrseq_simple.c
> @@ -7,6 +7,7 @@
> *
> * Simple MMC power sequence management
> */
> +#include <linux/clk.h>
> #include <linux/kernel.h>
> #include <linux/slab.h>
> #include <linux/device.h>
> @@ -20,6 +21,7 @@
>
> struct mmc_pwrseq_simple {
> struct mmc_pwrseq pwrseq;
> + struct clk *ext_clk;
You need to add a bool, maybe call it clk_enabled; See why below.
> int nr_gpios;
> struct gpio_desc *reset_gpios[0];
> };
> @@ -39,6 +41,9 @@ static void mmc_pwrseq_simple_pre_power_on(struct mmc_host *host)
> struct mmc_pwrseq_simple *pwrseq = container_of(host->pwrseq,
> struct mmc_pwrseq_simple, pwrseq);
>
> + if (!IS_ERR(pwrseq->ext_clk))
> + clk_prepare_enable(pwrseq->ext_clk);
> +
There are no guarantee that the ->mmc_pwrseq_simple_pre_power_on()
will be invoked prior ->mmc_pwrseq_simple_power_off().
That means you need to keep track of if you have gated/ungated the
clock. In other words check pwrseq->clk_enabled. That will prevent
potential clk unbalance issues.
> mmc_pwrseq_simple_set_gpios_value(pwrseq, 1);
> }
>
> @@ -50,6 +55,17 @@ static void mmc_pwrseq_simple_post_power_on(struct mmc_host *host)
> mmc_pwrseq_simple_set_gpios_value(pwrseq, 0);
> }
>
> +static void mmc_pwrseq_simple_power_off(struct mmc_host *host)
> +{
> + struct mmc_pwrseq_simple *pwrseq = container_of(host->pwrseq,
> + struct mmc_pwrseq_simple, pwrseq);
> +
> + mmc_pwrseq_simple_set_gpios_value(pwrseq, 1);
> +
> + if (!IS_ERR(pwrseq->ext_clk))
> + clk_disable_unprepare(pwrseq->ext_clk);
Same comment as above.
> +}
> +
> static void mmc_pwrseq_simple_free(struct mmc_host *host)
> {
> struct mmc_pwrseq_simple *pwrseq = container_of(host->pwrseq,
> @@ -60,6 +76,9 @@ static void mmc_pwrseq_simple_free(struct mmc_host *host)
> if (!IS_ERR(pwrseq->reset_gpios[i]))
> gpiod_put(pwrseq->reset_gpios[i]);
>
> + if (!IS_ERR(pwrseq->ext_clk))
> + clk_put(pwrseq->ext_clk);
> +
> kfree(pwrseq);
> host->pwrseq = NULL;
> }
> @@ -67,7 +86,7 @@ static void mmc_pwrseq_simple_free(struct mmc_host *host)
> static struct mmc_pwrseq_ops mmc_pwrseq_simple_ops = {
> .pre_power_on = mmc_pwrseq_simple_pre_power_on,
> .post_power_on = mmc_pwrseq_simple_post_power_on,
> - .power_off = mmc_pwrseq_simple_pre_power_on,
> + .power_off = mmc_pwrseq_simple_power_off,
> .free = mmc_pwrseq_simple_free,
> };
>
> @@ -85,6 +104,14 @@ int mmc_pwrseq_simple_alloc(struct mmc_host *host, struct device *dev)
> if (!pwrseq)
> return -ENOMEM;
>
> + pwrseq->ext_clk = clk_get(dev, "ext_clock");
> + if (IS_ERR(pwrseq->ext_clk) &&
> + PTR_ERR(pwrseq->ext_clk) != -ENOENT &&
> + PTR_ERR(pwrseq->ext_clk) != -ENOSYS) {
I don't think you can get -ENOSYS.
> + ret = PTR_ERR(pwrseq->ext_clk);
> + goto free;
> + }
> +
> for (i = 0; i < nr_gpios; i++) {
> pwrseq->reset_gpios[i] = gpiod_get_index(dev, "reset", i,
> GPIOD_OUT_HIGH);
> @@ -96,7 +123,7 @@ int mmc_pwrseq_simple_alloc(struct mmc_host *host, struct device *dev)
> while (--i)
> gpiod_put(pwrseq->reset_gpios[i]);
>
> - goto free;
> + goto clk_put;
> }
> }
>
> @@ -105,6 +132,9 @@ int mmc_pwrseq_simple_alloc(struct mmc_host *host, struct device *dev)
> host->pwrseq = &pwrseq->pwrseq;
>
> return 0;
> +clk_put:
> + if (!IS_ERR(pwrseq->ext_clk))
> + clk_put(pwrseq->ext_clk);
> free:
> kfree(pwrseq);
> return ret;
> --
> 2.1.3
>
Kind regards
Uffe
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