linux-kernel - Re: [PATCH v5 03/26] memory: omap-gpmc: Introduce GPMC to NAND interface

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Message-ID: <20160305013534.GJ55664@google.com>
Date:	Fri, 4 Mar 2016 17:35:34 -0800
From:	Brian Norris <computersforpeace@...il.com>
To:	Roger Quadros <rogerq@...com>
Cc:	tony@...mide.com, dwmw2@...radead.org,
	ezequiel@...guardiasur.com.ar, javier@...hile0.org, fcooper@...com,
	nsekhar@...com, linux-mtd@...ts.infradead.org,
	linux-omap@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 03/26] memory: omap-gpmc: Introduce GPMC to NAND
 interface

Hi Roger,

On Fri, Feb 19, 2016 at 11:15:25PM +0200, Roger Quadros wrote:
> The OMAP GPMC module has certain registers dedicated for NAND
> access and some NAND bits mixed with other GPMC functionality.
> 
> For the NAND dedicated registers we have the struct gpmc_nand_regs.
> 
> The NAND driver needs to access NAND specific bits from the
> following non-dedicated registers
> 1) FIFOEVENT and TERMCOUNT from GPMC_IRQENABLE and GPMC_IRQSTATUS
> 2) EMPTYWRITEBUFFERSTATUS from GPMC_STATUS
> 
> For accessing these bits we introduce the struct gpmc_nand_ops.
> 
> Rename the gpmc_update_nand_reg() API to gpmc_omap_get_nand_ops()
> and make it return the gpmc_nand_ops along with updating the
> gpmc_nand_regs. This API will be called by the OMAP NAND driver
> to access the necessary bits in GPMC register space.
> 
> Signed-off-by: Roger Quadros <rogerq@...com>
> ---
>  drivers/memory/omap-gpmc.c | 21 ++++++++++++++++++++
>  include/linux/omap-gpmc.h  | 49 ++++++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 68 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/memory/omap-gpmc.c b/drivers/memory/omap-gpmc.c
> index 6515dfc..c2f7320 100644
> --- a/drivers/memory/omap-gpmc.c
> +++ b/drivers/memory/omap-gpmc.c
> @@ -1098,6 +1098,27 @@ void gpmc_update_nand_reg(struct gpmc_nand_regs *reg, int cs)
>  	}
>  }
>  
> +static struct gpmc_nand_ops nand_ops;
> +
> +/**
> + * gpmc_omap_get_nand_ops - Get the GPMC NAND interface
> + * @regs: the GPMC NAND register map exclusive for NAND use.
> + * @cs: GPMC chip select number on which the NAND sits. The
> + *      register map returned will be specific to this chip select.
> + *
> + * Returns NULL on error e.g. invalid cs.
> + */
> +struct gpmc_nand_ops *gpmc_omap_get_nand_ops(struct gpmc_nand_regs *reg, int cs)
> +{
> +	if (cs >= gpmc_cs_num)
> +		return NULL;
> +
> +	gpmc_update_nand_reg(reg, cs);
> +
> +	return &nand_ops;
> +}
> +EXPORT_SYMBOL_GPL(gpmc_omap_get_nand_ops);
> +
>  int gpmc_get_client_irq(unsigned irq_config)
>  {
>  	int i;
> diff --git a/include/linux/omap-gpmc.h b/include/linux/omap-gpmc.h
> index 2dcef1c..7de9f9b 100644
> --- a/include/linux/omap-gpmc.h
> +++ b/include/linux/omap-gpmc.h
> @@ -14,14 +14,59 @@
>  #define GPMC_IRQ_FIFOEVENTENABLE	0x01
>  #define GPMC_IRQ_COUNT_EVENT		0x02
>  
> +enum gpmc_nand_irq {
> +	GPMC_NAND_IRQ_FIFOEVENT = 0,
> +	GPMC_NAND_IRQ_TERMCOUNT,
> +};
> +
> +/**
> + * gpmc_nand_ops - Interface between NAND and GPMC
> + * @nand_irq_enable: enable the requested GPMC NAND interrupt event.
> + * @nand_irq_disable: disable the requested GPMC NAND interrupt event.
> + * @nand_irq_clear: clears the GPMC NAND interrupt event status.
> + * @nand_irq_status: get the NAND interrupt event status.
> + * @nand_write_buffer_empty: get the NAND write buffer empty status.
> + */
> +struct gpmc_nand_ops {
> +	int (*nand_irq_enable)(enum gpmc_nand_irq irq);
> +	int (*nand_irq_disable)(enum gpmc_nand_irq irq);
> +	void (*nand_irq_clear)(enum gpmc_nand_irq irq);
> +	u32 (*nand_irq_status)(void);

^^ These 4 aren't being used in this revision?

> +	bool (*nand_writebuffer_empty)(void);
> +};
> +
> +struct gpmc_nand_regs;
> +
> +#if IS_ENABLED(CONFIG_OMAP_GPMC)
> +struct gpmc_nand_ops *gpmc_omap_get_nand_ops(struct gpmc_nand_regs *regs,
> +					     int cs);
> +#else
> +static inline gpmc_nand_ops *gpmc_omap_get_nand_ops(struct gpmc_nand_regs *regs,
> +						    int cs)
> +{
> +	return NULL;
> +}
> +#endif /* CONFIG_OMAP_GPMC */
> +
> +/*--------------------------------*/
> +
> +/* deprecated APIs */
> +#if IS_ENABLED(CONFIG_OMAP_GPMC)
> +void gpmc_update_nand_reg(struct gpmc_nand_regs *reg, int cs);
> +#else
> +static inline void gpmc_update_nand_reg(struct gpmc_nand_regs *reg, int cs)
> +{
> +	reg = NULL;

What are you trying to do here? 'reg' is local, so the assignment is
pointless.

> +}
> +#endif /* CONFIG_OMAP_GPMC */

Brian