Re: [PATCH v2 1/1] scsi: ufs: make UFS Tx lane1 clock optional for QCOM platforms

Doug Anderson
2018-10-11T20:21:46Z

Hi,

On Thu, Oct 11, 2018 at 5:33 AM Can Guo <cang@codeaurora.org> wrote:
> static int ufs_qcom_host_clk_get(struct device *dev,
> - const char *name, struct clk **clk_out)
> + const char *name, struct clk **clk_out, bool optional)
> {
> struct clk *clk;
> int err = 0;
>
> clk = devm_clk_get(dev, name);
> - if (IS_ERR(clk)) {
> + if (clk == ERR_PTR(-EPROBE_DEFER)) {
> + err = -EPROBE_DEFER;
> + dev_warn(dev, "required clock %s hasn't probed yet, err %d\n",
> + name, err);
> + } else if (IS_ERR(clk)) {
> + if (optional)
> + return 0;

Change this function to:

static int ufs_qcom_host_clk_get(struct device *dev,
const char *name, struct clk **clk_out, bool optional)
{
struct clk *clk;
int err;

clk = devm_clk_get(dev, name);
if (!IS_ERR(clk)) {
*clk_out = clk;
return 0;
}

err = PTR_ERR(clk);

if (optional && err == -ENOENT) {
*clk_out = NULL;
return 0;
}

if (err != -EPROBE_DEFER)
dev_err(dev, "failed to get %s err %d",
name, err);

return err;
}

Specifically:

* Typically it just spams the log to print something when you see an
-EPROBE_DEFER.

* If a clock is optional you should only consider things a success
only if "-ENOENT" was returned. All other errors should be considered
fatal.

* If a clock is optional it's slightly cleaner to set *clk_out to
NULL. I know you're initting global data that happened to already be
NULL by default, but it still feels nice for the abstraction of the
function to do this.

* Please don't pass __func__ to your error messages.

> err = PTR_ERR(clk);
> dev_err(dev, "%s: failed to get %s err %d",
> __func__, name, err);
> @@ -113,10 +119,10 @@ static void ufs_qcom_disable_lane_clks(struct ufs_qcom_host *host)
> if (!host->is_lane_clks_enabled)
> return;
>
> - if (host->hba->lanes_per_direction > 1)
> + if (host->tx_l1_sync_clk)

Remove this "if". Always call clk_disable_unprepare() which will be a
no-op if "host->tx_l1_sync_clk" is NULL. clk_disable_unprepare() is a
no-op for NULL clocks by design specifically to make code like this
cleaner.

> clk_disable_unprepare(host->tx_l1_sync_clk);
> clk_disable_unprepare(host->tx_l0_sync_clk);
> - if (host->hba->lanes_per_direction > 1)
> + if (host->rx_l1_sync_clk)

Remove this "if". Always call clk_disable_unprepare() which will be a
no-op if "host->rx_l1_sync_clk" is NULL. clk_disable_unprepare() is a
no-op for NULL clocks by design specifically to make code like this
cleaner.

> clk_disable_unprepare(host->rx_l1_sync_clk);
> clk_disable_unprepare(host->rx_l0_sync_clk);
>
> @@ -141,12 +147,14 @@ static int ufs_qcom_enable_lane_clks(struct ufs_qcom_host *host)
> if (err)
> goto disable_rx_l0;
>
> - if (host->hba->lanes_per_direction > 1) {
> + if (host->rx_l1_sync_clk) {

Remove this "if". Always call ufs_qcom_host_clk_enable(). The
clk_prepare_enable() inside ufs_qcom_host_clk_enable() will be a no-op
if "host->rx_l1_sync_clk" is NULL and will return 0 (no error).

> err = ufs_qcom_host_clk_enable(dev, "rx_lane1_sync_clk",
> host->rx_l1_sync_clk);
> if (err)
> goto disable_tx_l0;
> + }
>
> + if (host->tx_l1_sync_clk) {

Remove this "if". Always call ufs_qcom_host_clk_enable(). The
clk_prepare_enable() inside ufs_qcom_host_clk_enable() will be a no-op
if "host->tx_l1_sync_clk" is NULL and will return 0 (no error).

-Doug