Re: [u-boot][PATCH 04/14] mtd: rawnand: omap_gpmc: Optimize NAND reads

[Roger Quadros <rogerq@kernel.org>]

Hi Michael,

On 15/10/2022 10:24, Michael Nazzareno Trimarchi wrote:
> Hi
> 
> On Tue, Oct 11, 2022 at 1:50 PM Roger Quadros <rogerq@kernel.org> wrote:
>>
>> Rename omap_nand_read() to omap_nand_read_buf() to reflect
>> actual behaviour.
>>
>> Use FIFO read address instead of raw read address for reads.
>>
>> The GPMC automatically converts 32-bit/16-bit reads to NAND
>> device specific reads (8/16 bit). Use the largest possible
>> read granularity size for more efficient reads.
>>
>> Signed-off-by: Roger Quadros <rogerq@kernel.org>
>> ---
>>  drivers/mtd/nand/raw/omap_gpmc.c | 49 ++++++++++++++++++--------------
>>  1 file changed, 28 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/raw/omap_gpmc.c b/drivers/mtd/nand/raw/omap_gpmc.c
>> index d62c3e6fce..b36fe762b3 100644
>> --- a/drivers/mtd/nand/raw/omap_gpmc.c
>> +++ b/drivers/mtd/nand/raw/omap_gpmc.c
>> @@ -55,6 +55,7 @@ struct omap_nand_info {
>>         enum omap_ecc ecc_scheme;
>>         uint8_t cs;
>>         uint8_t ws;             /* wait status pin (0,1) */
>> +       void __iomem *fifo;
>>  };
>>
>>  /* We are wasting a bit of memory but al least we are safe */
>> @@ -350,6 +351,20 @@ static int omap_calculate_ecc(struct mtd_info *mtd, const uint8_t *dat,
>>         return 0;
>>  }
>>
>> +static inline void omap_nand_read_buf(struct mtd_info *mtd, uint8_t *buf, int len)
>> +{
>> +       struct nand_chip *chip = mtd_to_nand(mtd);
>> +       struct omap_nand_info *info = nand_get_controller_data(chip);
>> +       u32 alignment = ((uintptr_t)buf | len) & 3;
>> +
>> +       if (alignment & 1)
>> +               readsb(info->fifo, buf, len);
>> +       else if (alignment & 3)
>> +               readsw(info->fifo, buf, len >> 1);
>> +       else
>> +               readsl(info->fifo, buf, len >> 2);
>> +}
>> +
>>  #ifdef CONFIG_NAND_OMAP_GPMC_PREFETCH
>>
>>  #define PREFETCH_CONFIG1_CS_SHIFT      24
>> @@ -415,7 +430,7 @@ static int __read_prefetch_aligned(struct nand_chip *chip, uint32_t *buf, int le
>>                 cnt = PREFETCH_STATUS_FIFO_CNT(cnt);
>>
>>                 for (i = 0; i < cnt / 4; i++) {
>> -                       *buf++ = readl(CONFIG_SYS_NAND_BASE);
>> +                       *buf++ = readl(info->fifo);
>>                         len -= 4;
>>                 }
>>         } while (len);
>> @@ -425,16 +440,6 @@ static int __read_prefetch_aligned(struct nand_chip *chip, uint32_t *buf, int le
>>         return 0;
>>  }
>>
>> -static inline void omap_nand_read(struct mtd_info *mtd, uint8_t *buf, int len)
>> -{
>> -       struct nand_chip *chip = mtd_to_nand(mtd);
>> -
>> -       if (chip->options & NAND_BUSWIDTH_16)
>> -               nand_read_buf16(mtd, buf, len);
>> -       else
>> -               nand_read_buf(mtd, buf, len);
>> -}
>> -
>>  static void omap_nand_read_prefetch(struct mtd_info *mtd, uint8_t *buf, int len)
>>  {
>>         int ret;
>> @@ -447,7 +452,7 @@ static void omap_nand_read_prefetch(struct mtd_info *mtd, uint8_t *buf, int len)
>>          */
>>         head = ((uintptr_t)buf) % 4;
>>         if (head) {
>> -               omap_nand_read(mtd, buf, head);
>> +               omap_nand_read_buf(mtd, buf, head);
>>                 buf += head;
>>                 len -= head;
>>         }
>> @@ -461,10 +466,10 @@ static void omap_nand_read_prefetch(struct mtd_info *mtd, uint8_t *buf, int len)
>>         ret = __read_prefetch_aligned(chip, (uint32_t *)buf, len - tail);
>>         if (ret < 0) {
>>                 /* fallback in case the prefetch engine is busy */
>> -               omap_nand_read(mtd, buf, len);
>> +               omap_nand_read_buf(mtd, buf, len);
>>         } else if (tail) {
>>                 buf += len - tail;
>> -               omap_nand_read(mtd, buf, tail);
>> +               omap_nand_read_buf(mtd, buf, tail);
>>         }
>>  }
>>  #endif /* CONFIG_NAND_OMAP_GPMC_PREFETCH */
>> @@ -1001,6 +1006,8 @@ int board_nand_init(struct nand_chip *nand)
>>         int32_t gpmc_config = 0;
>>         int cs = cs_next++;
>>         int err = 0;
>> +       struct omap_nand_info *info;
>> +
>>         /*
>>          * xloader/Uboot's gpmc configuration would have configured GPMC for
>>          * nand type of memory. The following logic scans and latches on to the
>> @@ -1029,9 +1036,12 @@ int board_nand_init(struct nand_chip *nand)
>>
>>         nand->IO_ADDR_R = (void __iomem *)&gpmc_cfg->cs[cs].nand_dat;
>>         nand->IO_ADDR_W = (void __iomem *)&gpmc_cfg->cs[cs].nand_cmd;
>> -       omap_nand_info[cs].control = NULL;
>> -       omap_nand_info[cs].cs = cs;
>> -       omap_nand_info[cs].ws = wscfg[cs];
>> +
>> +       info = &omap_nand_info[cs];
>> +       info->control = NULL;
>> +       info->cs = cs;
>> +       info->ws = wscfg[cs];
>> +       info->fifo = (void __iomem *)CONFIG_SYS_NAND_BASE;
>>         nand_set_controller_data(nand, &omap_nand_info[cs]);
>>         nand->cmd_ctrl  = omap_nand_hwcontrol;
>>         nand->options   |= NAND_NO_PADDING | NAND_CACHEPRG;
>> @@ -1062,10 +1072,7 @@ int board_nand_init(struct nand_chip *nand)
>>  #ifdef CONFIG_NAND_OMAP_GPMC_PREFETCH
>>         nand->read_buf = omap_nand_read_prefetch;
>>  #else
>> -       if (nand->options & NAND_BUSWIDTH_16)
>> -               nand->read_buf = nand_read_buf16;
>> -       else
>> -               nand->read_buf = nand_read_buf;
>> +       nand->read_buf = omap_nand_read_buf;
>>  #endif
>>
>>         nand->dev_ready = omap_dev_ready;
>> --
>> 2.17.1
>>
> 
> Is possible for you to split in use of fifo and optimize read/alignment

Sure, I'll remember to do that when I re-spin this series.

> 
> Otherwise
> 
> Reviewed-by: Michael Trimarchi <michael@amarulasolutions.com>
> 
> 
Thanks!

--
cheers,
-roger