linux-kernel - Re: RFC: Driver for CB710/720 memory card reader (MMC part)

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Date:	Fri, 14 Nov 2008 22:06:58 +0100
From:	Pierre Ossman <drzeus-mmc@...eus.cx>
To:	Michał Mirosław <mirq-linux@...e.qmqm.pl>
Cc:	linux-kernel@...r.kernel.org, Alex Dubov <oakad@...oo.com>
Subject: Re: RFC: Driver for CB710/720 memory card reader (MMC part) - v3

On Wed, 29 Oct 2008 15:11:47 +0100
Michał Mirosław <mirq-linux@...e.qmqm.pl> wrote:

> Here is the driver for CB710 SD/MMC reader updated to recently released
> kernel version 2.6.27. The code is divided into PCI device driver
> (wrapped that registers three platform devices) and MMC reader driver.
> This idea was taken from TIFM driver.
> 
> Changes from v2:
>  - return EINVAL for unsupported data transfer sizes
>  - use sg_mapping_iter for PIO from/to scatterlist
>  - add slot release function and prevent kobject leak on device registration's
>    error path
> 
> If this code looks reasonably good, then I'll post patches against the
> real kernel tree. The file distribution plan is:
> 

It looks more or less good to go. I have some small notes, and you
probably need to poke some scatterlist folks to okay those changes
(should probably be a separate patch).

> +/* slot port accessors - in case it turns out inX() is all that is needed */
> +#define CB710_PORT_ACCESSORS(t) \
> +static inline void cb710_write_port_##t(struct cb710_slot *slot,	\
> +	unsigned port, u##t value)					\
> +{									\
> +	iowrite##t(value, slot->iobase + port);				\
> +}									\
> +									\
> +static inline u##t cb710_read_port_##t(struct cb710_slot *slot,		\
> +	unsigned port)							\
> +{									\
> +	return ioread##t(slot->iobase + port);				\
> +}									\
> +									\
> +static inline void cb710_modify_port_##t(struct cb710_slot *slot,	\
> +	unsigned port, u##t set, u##t clear)				\
> +{									\
> +	iowrite##t(							\
> +		(ioread##t(slot->iobase + port) & ~clear)|set,		\
> +		slot->iobase + port);					\
> +}
> +
> +CB710_PORT_ACCESSORS(8)
> +CB710_PORT_ACCESSORS(16)
> +CB710_PORT_ACCESSORS(32)

This is clearer than what you had before, but I still think you should
consider using the kernel functions directly.

> +/* helper functions */
> +
> +static inline void cb710_set_irq_handler(struct cb710_slot *slot,
> +	cb710_irq_handler_t handler)
> +{
> +	rcu_assign_pointer(slot->irq_handler, handler);
> +	synchronize_rcu();	/* sync to IRQ handler */
> +}
> +

Why RCU:s? This smells of premature optimisation.

> +/* per-MMC-reader structure */
> +struct cb710_mmc_reader {
> +	struct tasklet_struct finish_req_tasklet;
> +	struct mmc_request *mrq;
> +	spinlock_t irq_lock;
> +	unsigned char last_power_mode;
> +#ifdef VERBOSE_DEBUG
> +	spinlock_t serialization_lock;
> +	unsigned char active_req, active_ios;
> +#endif
> +};

I couldn't find VERBOSE_DEBUG defined somewhere. For ease of use with
future testers, you should connect it to some Kconfig option.

> +static int cb710_suspend(struct pci_dev *pdev, pm_message_t state)
> +{
> +	pci_save_state(pdev);
> +	pci_disable_device(pdev);
> +	if (state.event & PM_EVENT_SLEEP)
> +		pci_set_power_state(pdev, PCI_D3cold);
> +	return 0;
> +}
> +
> +static int cb710_resume(struct pci_dev *pdev)
> +{
> +	pci_set_power_state(pdev, PCI_D0);
> +	pci_restore_state(pdev);
> +	return pcim_enable_device(pdev);
> +}

Free/restore interrupt?

> +/* TODO: move to pci_ids.h before merging upstream */
> +#define PCI_DEVICE_ID_ENE_710_FLASH	0x0510

It's a matter of taste really. Many drivers have their defines in the
driver. Personally I think it is nice to have everything in pci_ids.h,
but it's up to you really.

> +#if 0
> +	/* original driver set bit 14 for MMC/SD application
> +	 * commands. There's no difference 'on the wire' and
> +	 * it apparently works without it anyway.
> +	 */
> +	if (flags & MMC_CMD_IS_APPCMD)
> +		cb_flags |= 0x4000;
> +#endif

As this code is just useless, please clean it out before you submit the
driver.

> +	mmc->ops = &cb710_mmc_host;
> +	mmc->f_max = val;
> +	mmc->f_min = val >> cb710_clock_divider_log2[CB710_MAX_DIVIDER_IDX];
> +	mmc->ocr_avail = MMC_VDD_32_33|MMC_VDD_33_34|MMC_VDD_34_35;

Since you can't change the voltage, this seems wrong. My guess is that
the MMC_VDD_34_35 define should go.

> +static int __devexit cb710_mmc_exit(struct platform_device *pdev)
> +{
> +	struct cb710_slot *slot = cb710_pdev_to_slot(pdev);
> +	struct mmc_host *mmc = cb710_slot_to_mmc(slot);
> +	struct cb710_mmc_reader *reader = mmc_priv(mmc);
> +
> +	mmc_remove_host(mmc);
> +
> +	/* XXX what if IRQ arrives now? */

Most drivers handle this by sticking their head in the sand, but the
proper way is probably to disable the card insertions interrupt before
mmc_remove_host().

(and there should be no other unsolicited interrupts)

Rgds
-- 
     -- Pierre Ossman

  Linux kernel, MMC maintainer        http://www.kernel.org
  rdesktop, core developer          http://www.rdesktop.org

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