Re: [PATCH 2/2] mmc: dw_mmc: Handle wp-gpios from device tree

Doug Anderson
2012-11-22T20:59:15Z

Jaehoon,

Thanks for the review. See below for comments. I'll plan on a new
patch either Monday or Tuesday when I have a chance to spin and
re-test.

On Wed, Nov 21, 2012 at 5:55 PM, Jaehoon Chung <jh80.chung@samsung.com> wrote:
> On 11/22/2012 07:03 AM, Doug Anderson wrote:
>> On some SoCs (like exynos5250) you need to use an external GPIO for
>> write protect. Add support for wp-gpios to the core dw_mmc driver
>> since it could be useful across multiple SoCs.
>>
>> With this change I am able to make use of the write protect for the
>> external SD slot on exynos5250-snow.
>>
>> Signed-off-by: Doug Anderson <dianders@chromium.org>
>> ---
>> drivers/mmc/host/dw_mmc.c | 35 +++++++++++++++++++++++++++++++++++
>> 1 files changed, 35 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>> index 5b41348..9c79870 100644
>> --- a/drivers/mmc/host/dw_mmc.c
>> +++ b/drivers/mmc/host/dw_mmc.c
>> @@ -34,6 +34,7 @@
>> #include <linux/regulator/consumer.h>
>> #include <linux/workqueue.h>
>> #include <linux/of.h>
>> +#include <linux/of_gpio.h>
>>
>> #include "dw_mmc.h"
>>
>> @@ -74,6 +75,7 @@ struct idmac_desc {
>> * struct dw_mci_slot - MMC slot state
>> * @mmc: The mmc_host representing this slot.
>> * @host: The MMC controller this slot is using.
>> + * @wp_gpio: If gpio_is_valid() we'll use this to read write protect.
>> * @ctype: Card type for this slot.
>> * @mrq: mmc_request currently being processed or waiting to be
>> * processed, or NULL when the slot is idle.
>> @@ -88,6 +90,8 @@ struct dw_mci_slot {
>> struct mmc_host *mmc;
>> struct dw_mci *host;
>>
>> + int wp_gpio;
>> +
>> u32 ctype;
>>
>> struct mmc_request *mrq;
>> @@ -832,6 +836,8 @@ static int dw_mci_get_ro(struct mmc_host *mmc)
>> read_only = 0;
>> else if (brd->get_ro)
>> read_only = brd->get_ro(slot->id);
>> + else if (gpio_is_valid(slot->wp_gpio))
>> + read_only = gpio_get_value(slot->wp_gpio);
>> else
>> read_only =
>> mci_readl(slot->host, WRTPRT) & (1 << slot->id) ? 1 : 0;
>> @@ -1802,6 +1808,29 @@ static u32 dw_mci_of_get_bus_wd(struct device *dev, u8 slot)
>> " as 1\n");
>> return bus_wd;
>> }
>> +
>> +/* find the write protect gpio for a given slot; or -1 if none specified */
>> +static u32 dw_mci_of_get_wp_gpio(struct device *dev, u8 slot)
>> +{
>> + struct device_node *np = dw_mci_of_find_slot_node(dev, slot);
>> + int gpio;
>> +
>> + if (!np)
>> + return -1;
> I think good that use the error number instead of -1. Also the below code.

In this case it's not really returning an error code which is why I
chose -1. It's returning a gpio number or anything that is a sentinel
value indicating that the GPIO is not valid.

...but you're right, an error code would work. I'll replace with
"-EINVAL" in my next patch.

>
>> +
>> + gpio = of_get_named_gpio(np, "wp-gpios", 0);
>> +
>> + /* Having a missing entry is valid; return silently */
>> + if (!gpio_is_valid(gpio))
>> + return -1;
>> +
>> + if (devm_gpio_request(dev, gpio, "dw-mci-wp")) {
>> + dev_warn(dev, "gpio [%d] request failed\n", gpio);
>> + return -1;
>> + }
>> +
>> + return gpio;
> gpio is int type, but return type is u32?

Good catch. Will fix.

>
> Best Regards,
> Jaehoon Chung
>> +}
>> #else /* CONFIG_OF */
>> static u32 dw_mci_of_get_bus_wd(struct device *dev, u8 slot)
>> {
>> @@ -1811,6 +1840,10 @@ static struct device_node *dw_mci_of_find_slot_node(struct device *dev, u8 slot)
>> {
>> return NULL;
>> }
>> +static u32 dw_mci_of_get_wp_gpio(struct device *dev, u8 slot)
>> +{
>> + return -1;
>> +}
>> #endif /* CONFIG_OF */
>>
>> static int dw_mci_init_slot(struct dw_mci *host, unsigned int id)
>> @@ -1923,6 +1956,8 @@ static int dw_mci_init_slot(struct dw_mci *host, unsigned int id)
>> else
>> clear_bit(DW_MMC_CARD_PRESENT, &slot->flags);
>>
>> + slot->wp_gpio = dw_mci_of_get_wp_gpio(host->dev, slot->id);
>> +
>> mmc_add_host(mmc);
>>
>> #if defined(CONFIG_DEBUG_FS)
>>
>