Re: [PATCH V1 02/11] mmc: sdhci: allow host to specify maximum tuning loops

Adrian Hunter
2019-03-08T11:52:03Z

On 2/03/19 7:20 AM, Sowjanya Komatineni wrote:
> As per the Host Controller Standard Specification Version 4.20,
> limitation of tuning iteration count is removed as PLL locking
> time can be longer than UHS-1 tuning due to larger PVT fluctuation
> and it will result in increase of tuning iteration to complete the
> tuning.
>
> This patch creates a hook get_max_tuning_loop_count to allow hosts
> to specify maximum tuning iterations and updates execute_tuning
> to use the specified maximum tuning iteration count.
>
> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
> ---
> drivers/mmc/host/sdhci.c | 7 +++++--
> drivers/mmc/host/sdhci.h | 1 +
> 2 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index a8141ff9be03..e9e919218006 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -2366,12 +2366,15 @@ EXPORT_SYMBOL_GPL(sdhci_send_tuning);
> static int __sdhci_execute_tuning(struct sdhci_host *host, u32 opcode)
> {
> int i;
> + int tuning_loop_count = MAX_TUNING_LOOP;
>
> + if (host->ops->get_max_tuning_loop_count)
> + tuning_loop_count = host->ops->get_max_tuning_loop_count(host);

I would prefer to make tuning_loop_count a sdhci_host member initialized to
MAX_TUNING_LOOP in sdhci_alloc_host().

Then hook .execute_tuning e.g.

host->mmc_host_ops.execute_tuning = tegra_sdhci_execute_tuning;

and set up host->tuning_loop_count

> /*
> * Issue opcode repeatedly till Execute Tuning is set to 0 or the number
> - * of loops reaches 40 times.
> + * of loops reaches tuning loop count.
> */
> - for (i = 0; i < MAX_TUNING_LOOP; i++) {
> + for (i = 0; i < tuning_loop_count; i++) {
> u16 ctrl;
>
> sdhci_send_tuning(host, opcode);
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> index 01002cba1359..c80e0d6f9b10 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -638,6 +638,7 @@ struct sdhci_ops {
> unsigned int (*get_ro)(struct sdhci_host *host);
> void (*reset)(struct sdhci_host *host, u8 mask);
> int (*platform_execute_tuning)(struct sdhci_host *host, u32 opcode);
> + int (*get_max_tuning_loop_count)(struct sdhci_host *host);
> void (*set_uhs_signaling)(struct sdhci_host *host, unsigned int uhs);
> void (*hw_reset)(struct sdhci_host *host);
> void (*adma_workaround)(struct sdhci_host *host, u32 intmask);
>