[U-Boot] [PATCH 5/6] tegra: nand: Add Tegra NAND driver

[Simon Glass]

Hi Stephen,

On Fri, Jan 20, 2012 at 9:31 AM, Stephen Warren <swarren at nvidia.com> wrote:
> On 01/13/2012 04:10 PM, Simon Glass wrote:
>> From: Jim Lin <jilin at nvidia.com>
>>
>> A device tree is used to configure the NAND, including memory
>> timings and block/pages sizes.
>>
>> If this node is not present or is disabled, then NAND will not
>> be initialized.
>>
>> Signed-off-by: Simon Glass <sjg at chromium.org>
>
>> diff --git a/drivers/mtd/nand/tegra2_nand.c b/drivers/mtd/nand/tegra2_nand.c
>
>> +/**
>> + * Wait for command completion
>> + *
>> + * @param reg  nand_ctlr structure
>> + * @return
>> + *     1 - Command completed
>> + *     0 - Timeout
>> + */
>> +static int nand_waitfor_cmd_completion(struct nand_ctlr *reg)
>> +{
>> +       int i;
>> +       u32 reg_val;
>> +
>> +       for (i = 0; i < NAND_CMD_TIMEOUT_MS * 1000; i++) {
>> +               if ((readl(&reg->command) & CMD_GO) ||
>> +                       !(readl(&reg->status) &
>> +                               STATUS_RBSY0) ||
>> +                       !(readl(&reg->isr) &
>> +                               ISR_IS_CMD_DONE)) {
>> +                       udelay(1);
>> +                       continue;
>> +               }
>> +               reg_val = readl(&reg->dma_mst_ctrl);
>> +               /*
>> +                * If DMA_MST_CTRL_EN_A_ENABLE or
>> +                * DMA_MST_CTRL_EN_B_ENABLE is set,
>> +                * that means DMA engine is running, then we
>> +                * have to wait until
>> +                * DMA_MST_CTRL_IS_DMA_DONE
>> +                * is cleared for DMA transfer completion.
>> +                */
>> +               if (reg_val & (DMA_MST_CTRL_EN_A_ENABLE |
>> +                       DMA_MST_CTRL_EN_B_ENABLE)) {
>> +                       if (reg_val & DMA_MST_CTRL_IS_DMA_DONE)
>> +                               return 1;
>> +               } else
>> +                       return 1;
>> +               udelay(1);
>
>
> To be more consistent with the first if/continue block, wouldn't it be
> better to recast that last if test and udelay as:
>
>               if (reg_val & (DMA_MST_CTRL_EN_A_ENABLE |
>                       DMA_MST_CTRL_EN_B_ENABLE)) {
>                       if (!(reg_val & DMA_MST_CTRL_IS_DMA_DONE)) {
>                               udelay(1);
>                               continue;
>                       }
>               }
>
>               break;

Yes that is better - but I've split it up a bit as it is too ugly.
Also I do want to actually make use of the udelay that is there,
rather than breaking out of the loop by default.

>
>
>> +/**
>> + * [DEFAULT] Send command to NAND device
>> + *
>> + * @param mtd          MTD device structure
>> + * @param command      the command to be sent
>> + * @param column       the column address for this command, -1 if none
>> + * @param page_addr    the page address for this command, -1 if none
>> + */
>> +static void nand_command(struct mtd_info *mtd, unsigned int command,
>> +       int column, int page_addr)
>> +{
>> +       register struct nand_chip *chip = mtd->priv;
>> +       struct nand_info *info;
>> +
>> +       info = (struct nand_info *) chip->priv;
>> +
>> +       /*
>> +        * Write out the command to the device.
>> +        */
>> +       if (mtd->writesize < 2048) {
>> +               /*
>> +                * Only command NAND_CMD_RESET or NAND_CMD_READID will come
>> +                * here before mtd->writesize is initialized, we don't have
>> +                * any action here because page size of NAND HY27UF084G2B
>> +                * is 2048 bytes and mtd->writesize will be 2048 after
>> +                * initialized.
>> +                */
>
> What if the NAND flash doesn't have a page size of 2048 bytes? The
> driver shouldn't make such assumptions about the flash chip that happens
> to be connected. Should the if above be:
>
>    if (mtd->writesize == 0)
>
> to be generic?

Well I have just removed this, as Scott suggested.

>
> Should this if branch validate that the command being executed is a
> legitimate command for the not-yet-fully-initialized case?

Removed

>
>> +/**
>> + * Set up NAND bus width and page size
>> + *
>> + * @param info         nand_info structure
>> + * @param *reg_val     address of reg_val
>> + * @return none - value is set in reg_val
>> + */
>> +static void set_bus_width_page_size(struct fdt_nand *config,
>> +       u32 *reg_val)
>> +{
>> +       if (config->width == 8)
>> +               *reg_val = CFG_BUS_WIDTH_8BIT;
>> +       else
>
> Shouldn't that be else if (config->width == 16)
>
>> +               *reg_val = CFG_BUS_WIDTH_16BIT;
>
>
> ... and there be an else clause that returns an error?

Done, have also called it from init as Scott suggests.

>
>> +
>> +       if (config->page_data_bytes == 256)
>> +               *reg_val |= CFG_PAGE_SIZE_256;
>> +       else if (config->page_data_bytes == 512)
>> +               *reg_val |= CFG_PAGE_SIZE_512;
>> +       else if (config->page_data_bytes == 1024)
>> +               *reg_val |= CFG_PAGE_SIZE_1024;
>> +       else if (config->page_data_bytes == 2048)
>> +               *reg_val |= CFG_PAGE_SIZE_2048;
>
> And similarly, and else clause that returns an error here?

Done

>
> --
> nvpublic

Regards,
Simon