Hi Kevin,
On 07/12/12 02:00, Kevin Hilman wrote:
> Hi Igor,
>
> Igor Grinberg <grinberg@xxxxxxxxxxxxxx> writes:
>
>> In case a board provides the gpio_pendown and not board_pdata,
>> the GPIO debounce is not taken care of.
>> Fix this by taking care of GPIO debounce in any case.
>>
>> Signed-off-by: Igor Grinberg <grinberg@xxxxxxxxxxxxxx>
>
> I just notice this this patch causing some faults in current l-o master
> branch.
This was not the case by the time I did the patch...
>
>> ---
>> arch/arm/mach-omap2/common-board-devices.c | 22 ++++++++++++----------
>> 1 files changed, 12 insertions(+), 10 deletions(-)
>>
>> diff --git a/arch/arm/mach-omap2/common-board-devices.c b/arch/arm/mach-omap2/common-board-devices.c
>> index 1706ebc..c187586 100644
>> --- a/arch/arm/mach-omap2/common-board-devices.c
>> +++ b/arch/arm/mach-omap2/common-board-devices.c
>> @@ -63,28 +63,30 @@ void __init omap_ads7846_init(int bus_num, int gpio_pendown, int gpio_debounce,
>> struct spi_board_info *spi_bi = &ads7846_spi_board_info;
>> int err;
>>
>> - if (board_pdata && board_pdata->get_pendown_state) {
>> - err = gpio_request_one(gpio_pendown, GPIOF_IN, "TSPenDown");
>> - if (err) {
>> - pr_err("Couldn't obtain gpio for TSPenDown: %d\n", err);
>> - return;
>> - }
>> - gpio_export(gpio_pendown, 0);
>> -
>> - if (gpio_debounce)
>> - gpio_set_debounce(gpio_pendown, gpio_debounce);
>> + err = gpio_request_one(gpio_pendown, GPIOF_IN, "TSPenDown");
>> + if (err) {
>> + pr_err("Couldn't obtain gpio for TSPenDown: %d\n", err);
>> + return;
>> }
>>
>> + if (gpio_debounce)
>> + gpio_set_debounce(gpio_pendown, gpio_debounce);
>> +
>> spi_bi->bus_num = bus_num;
>> spi_bi->irq = gpio_to_irq(gpio_pendown);
>>
>> if (board_pdata) {
>> board_pdata->gpio_pendown = gpio_pendown;
>> spi_bi->platform_data = board_pdata;
>> + if (board_pdata->get_pendown_state)
>> + gpio_export(gpio_pendown, 0);
>> } else {
>> ads7846_config.gpio_pendown = gpio_pendown;
>> }
>>
>> + if (!board_pdata || (board_pdata && !board_pdata->get_pendown_state))
>> + gpio_free(gpio_pendown);
>
> The logic here for freeing the GPIO doesn't make any sense to me.
> IIUC, the gpio_pendown is always used, so should not be freed.
The gpio_pendown is requested by the ads7846 driver and
of course you can't request the GPIO second time, so the driver failed.
>
> Moreover, if this GPIO is freed, that allows that GPIO bank to runtime
> suspend if there are no other GPIOs in use in that bank. So the first
> attempt to use the GPIO will fault.
The ads7846 driver requests the GPIO prior to using it.
>
> For example, on my Overo board(s), I noticed this failing as soon as teh
> ads7846 driver probes, requests the IRQ and the GPIO triggering is set.
Prior to requesting the IRQ, the ads7846_setup_pendown(spi, ts) method
is called, which requests the GPIO.
>
> Getting rid of this free fixes the problem.
But then don't you have double requesting?
>
> The changelog doesn't describe why the GPIO is freed here so I'm not
> sure I follow, but it seems to me that once this GPIO is requesed, it
> should not be freed as long as it's used, otherwise PM faults can occur.
It is not used until the ads7846 driver probes.
>
> Kevin
>
>>From bb87c3b5586950e480d0699504997a9ad587fd85 Mon Sep 17 00:00:00 2001
> From: Kevin Hilman <khilman@xxxxxx>
> Date: Wed, 11 Jul 2012 15:47:29 -0700
> Subject: [PATCH] ARM: OMAP2+: ads7846 init: fix fault caused by freeing
> pen-down GPIO
>
> commit 97ee9f01d6 (ARM: OMAP: fix the ads7846 init code) mistakenly
> frees the pen-down GPIO even though it will be used by the ads7846
> driver.
>
> Freeing a GPIO means that the GPIO bank containing that GPIO can be
> runtime suspended if its the last/only GPIO being used in that bank.
> If the GPIO bank is runtime suspended, any accesses to that bank will
> cause faults.
>
> Because the current code frees the GPIO, the ads7846 driver probe will
> fault when it requests its IRQ line. Because the IRQ is a GPIO line,
> the request IRQ will trickle down into the OMAP GPIO layer:
> gpio_irq_type() --> _set_gpio_triggering() which can fault if the
> bank has been runtime suspended.
>
> This is exctly what happens on Overo platforms (3530 Water, 3730 Overo
> FireSTORM) since this is the only GPIO used in the bank.
>
> To fix, don't free the GPIO at all since it is always in use.
>
> Cc: Igor Grinberg <grinberg@xxxxxxxxxxxxxx>
> Signed-off-by: Kevin Hilman <khilman@xxxxxx>
> ---
> arch/arm/mach-omap2/common-board-devices.c | 3 ---
> 1 file changed, 3 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/common-board-devices.c b/arch/arm/mach-omap2/common-board-devices.c
> index c187586..1ae6fd6 100644
> --- a/arch/arm/mach-omap2/common-board-devices.c
> +++ b/arch/arm/mach-omap2/common-board-devices.c
> @@ -84,9 +84,6 @@ void __init omap_ads7846_init(int bus_num, int gpio_pendown, int gpio_debounce,
> ads7846_config.gpio_pendown = gpio_pendown;
> }
>
> - if (!board_pdata || (board_pdata && !board_pdata->get_pendown_state))
> - gpio_free(gpio_pendown);
> -
> spi_register_board_info(&ads7846_spi_board_info, 1);
> }
> #else
--
Regards,
Igor.
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