Le dim. 7 mars 2021 à 17:07, Paul Cercueil <paul@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
---
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
