| Message ID | 20210307170742.70949-1-paul@crapouillou.net |
|---|---|
| Headers | show |
| Series | mmc: jz4740: Support PLL frequency changes | expand |
Le dim. 7 mars 2021 à 17:07, Paul Cercueil <paul@crapouillou.net> a écrit : > The main PLL can have its rate changed at any moment. To keep the MMC > clock running at a rate that fits the specifications, we need to > recompute the MMC clock rate every time the PLL rate changes. > > Use a mutex to ensure that the MMC is idle before performing the PLL > and > MMC rate changes. > > Signed-off-by: Paul Cercueil <paul@crapouillou.net> > --- > drivers/mmc/host/jz4740_mmc.c | 70 > ++++++++++++++++++++++++++++++++++- > 1 file changed, 69 insertions(+), 1 deletion(-) > > diff --git a/drivers/mmc/host/jz4740_mmc.c > b/drivers/mmc/host/jz4740_mmc.c > index b3c636edbb46..1197b8c6b6ed 100644 > --- a/drivers/mmc/host/jz4740_mmc.c > +++ b/drivers/mmc/host/jz4740_mmc.c > @@ -18,6 +18,7 @@ > #include <linux/mmc/host.h> > #include <linux/mmc/slot-gpio.h> > #include <linux/module.h> > +#include <linux/mutex.h> > #include <linux/of_device.h> > #include <linux/pinctrl/consumer.h> > #include <linux/platform_device.h> > @@ -149,6 +150,10 @@ struct jz4740_mmc_host { > struct platform_device *pdev; > struct clk *clk; > > + atomic_t clk_mutex_count; > + struct mutex clk_mutex; > + struct notifier_block clock_nb; > + > enum jz4740_mmc_version version; > > int irq; > @@ -338,6 +343,9 @@ static void jz4740_mmc_pre_request(struct > mmc_host *mmc, > struct jz4740_mmc_host *host = mmc_priv(mmc); > struct mmc_data *data = mrq->data; > > + if (atomic_inc_and_test(&host->clk_mutex_count)) > + mutex_lock(&host->clk_mutex); There's an obvious race here, let me rewrite this using the proper locking mechanism. -Paul > + > if (!host->use_dma) > return; > > @@ -353,6 +361,9 @@ static void jz4740_mmc_post_request(struct > mmc_host *mmc, > struct jz4740_mmc_host *host = mmc_priv(mmc); > struct mmc_data *data = mrq->data; > > + if (atomic_dec_return(&host->clk_mutex_count) == -1) > + mutex_unlock(&host->clk_mutex); > + > if (data && data->host_cookie != COOKIE_UNMAPPED) > jz4740_mmc_dma_unmap(host, data); > > @@ -955,6 +966,48 @@ static const struct mmc_host_ops jz4740_mmc_ops > = { > .enable_sdio_irq = jz4740_mmc_enable_sdio_irq, > }; > > +static inline struct jz4740_mmc_host * > +jz4740_mmc_nb_get_priv(struct notifier_block *nb) > +{ > + return container_of(nb, struct jz4740_mmc_host, clock_nb); > +} > + > +static struct clk *jz4740_mmc_get_parent_clk(struct clk *clk) > +{ > + /* > + * Return the first clock above the one that will effectively modify > + * its rate when clk_set_rate(clk) is called. > + */ > + clk = clk_get_first_to_set_rate(clk); > + > + return clk_get_parent(clk); > +} > + > +static int jz4740_mmc_update_clk(struct notifier_block *nb, > + unsigned long action, > + void *data) > +{ > + struct jz4740_mmc_host *host = jz4740_mmc_nb_get_priv(nb); > + > + /* > + * PLL may have changed its frequency; our clock may be running > above > + * spec. Wait until MMC is idle (using host->clk_mutex) before > changing > + * the PLL clock, and after it's done, reset our clock rate. > + */ > + > + switch (action) { > + case PRE_RATE_CHANGE: > + mutex_lock(&host->clk_mutex); > + break; > + default: > + clk_set_rate(host->clk, host->mmc->f_max); > + mutex_unlock(&host->clk_mutex); > + break; > + } > + > + return NOTIFY_OK; > +} > + > static const struct of_device_id jz4740_mmc_of_match[] = { > { .compatible = "ingenic,jz4740-mmc", .data = (void *) > JZ_MMC_JZ4740 }, > { .compatible = "ingenic,jz4725b-mmc", .data = (void > *)JZ_MMC_JZ4725B }, > @@ -971,6 +1024,7 @@ static int jz4740_mmc_probe(struct > platform_device* pdev) > struct mmc_host *mmc; > struct jz4740_mmc_host *host; > const struct of_device_id *match; > + struct clk *parent_clk; > > mmc = mmc_alloc_host(sizeof(struct jz4740_mmc_host), &pdev->dev); > if (!mmc) { > @@ -1058,12 +1112,24 @@ static int jz4740_mmc_probe(struct > platform_device* pdev) > goto err_free_irq; > host->use_dma = !ret; > > + atomic_set(&host->clk_mutex_count, -1); > + mutex_init(&host->clk_mutex); > + host->clock_nb.notifier_call = jz4740_mmc_update_clk; > + > + parent_clk = jz4740_mmc_get_parent_clk(host->clk); > + > + ret = clk_notifier_register(parent_clk, &host->clock_nb); > + if (ret) { > + dev_err(&pdev->dev, "Unable to register clock notifier\n"); > + goto err_release_dma; > + } > + > platform_set_drvdata(pdev, host); > ret = mmc_add_host(mmc); > > if (ret) { > dev_err(&pdev->dev, "Failed to add mmc host: %d\n", ret); > - goto err_release_dma; > + goto err_unregister_clk_notifier; > } > dev_info(&pdev->dev, "Ingenic SD/MMC card driver registered\n"); > > @@ -1074,6 +1140,8 @@ static int jz4740_mmc_probe(struct > platform_device* pdev) > > return 0; > > +err_unregister_clk_notifier: > + clk_notifier_unregister(parent_clk, &host->clock_nb); > err_release_dma: > if (host->use_dma) > jz4740_mmc_release_dma_channels(host); > -- > 2.30.1 >