Re: [PATCH] scsi: ufs-pci: Add LTR support for Intel controllers

[Adrian Hunter]

On 26/08/20 9:13 am, Avri Altman wrote:
>  
>>
>> Intel host controllers support the setting of latency tolerance.
>> Accordingly, implement the PM QoS ->set_latency_tolerance() callback. The
>> raw register values are also exposed via debugfs.
>>
>> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> Reviewed-by: Avri Altman <avri.altman@xxxxxxx>

Thanks for the quick review!

I will send a V2, refer below

> 
> Some nits below.
> 
> Thanks,
> Avri
> 
>> ---
>>  drivers/scsi/ufs/ufshcd-pci.c | 122 +++++++++++++++++++++++++++++++++-
>>  1 file changed, 120 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/scsi/ufs/ufshcd-pci.c b/drivers/scsi/ufs/ufshcd-pci.c
>> index 5a95a7bfbab0..e10f05013ae6 100644
>> --- a/drivers/scsi/ufs/ufshcd-pci.c
>> +++ b/drivers/scsi/ufs/ufshcd-pci.c
>> @@ -13,6 +13,14 @@
>>  #include "ufshcd.h"
>>  #include <linux/pci.h>
>>  #include <linux/pm_runtime.h>
>> +#include <linux/pm_qos.h>
>> +#include <linux/debugfs.h>
>> +
>> +struct intel_host {
>> +       u32             active_ltr;
>> +       u32             idle_ltr;
>> +       struct dentry   *debugfs_root;
>> +};
>>
>>  static int ufs_intel_disable_lcc(struct ufs_hba *hba)
>>  {
>> @@ -44,20 +52,129 @@ static int ufs_intel_link_startup_notify(struct ufs_hba
>> *hba,
>>         return err;
>>  }
>>
>> +#define INTEL_ACTIVELTR                0x804
>> +#define INTEL_IDLELTR          0x808
>> +
>> +#define INTEL_LTR_REQ          BIT(15)
>> +#define INTEL_LTR_SCALE_MASK   GENMASK(11, 10)
>> +#define INTEL_LTR_SCALE_1US    (2 << 10)
>> +#define INTEL_LTR_SCALE_32US   (3 << 10)
>> +#define INTEL_LTR_VALUE_MASK   GENMASK(9, 0)
>> +
>> +static void intel_cache_ltr(struct ufs_hba *hba)
>> +{
>> +       struct intel_host *host = ufshcd_get_variant(hba);
>> +
>> +       host->active_ltr = readl(hba->mmio_base + INTEL_ACTIVELTR);
>> +       host->idle_ltr = readl(hba->mmio_base + INTEL_IDLELTR);
> You might want to use the standard ufshcd_readl

LTR is more of a PCI concept, not directly related to UFS, so I am relucant
to use ufshcd_readl which implies a closer relationship to UFS.

> 
>> +}
>> +
>> +static void intel_ltr_set(struct device *dev, s32 val)
>> +{
>> +       struct ufs_hba *hba = dev_get_drvdata(dev);
>> +       struct intel_host *host = ufshcd_get_variant(hba);
>> +       u32 ltr;
>> +
>> +       pm_runtime_get_sync(dev);
>> +
>> +       /*
>> +        * Program latency tolerance (LTR) accordingly what has been asked
>> +        * by the PM QoS layer or disable it in case we were passed
>> +        * negative value or PM_QOS_LATENCY_ANY.
>> +        */
>> +       ltr = readl(hba->mmio_base + INTEL_ACTIVELTR);
>> +
>> +       if (val == PM_QOS_LATENCY_ANY || val < 0) {
>> +               ltr &= ~INTEL_LTR_REQ;
>> +       } else {
>> +               ltr |= INTEL_LTR_REQ;
>> +               ltr &= ~INTEL_LTR_SCALE_MASK;
>> +               ltr &= ~INTEL_LTR_VALUE_MASK;
>> +
>> +               if (val > INTEL_LTR_VALUE_MASK) {
>> +                       val >>= 5;
>> +                       if (val > INTEL_LTR_VALUE_MASK)
>> +                               val = INTEL_LTR_VALUE_MASK;
>> +                       ltr |= INTEL_LTR_SCALE_32US | val;
>> +               } else {
>> +                       ltr |= INTEL_LTR_SCALE_1US | val;
>> +               }
>> +       }
>> +
>> +       if (ltr == host->active_ltr)
>> +               goto out;
>> +
>> +       writel(ltr, hba->mmio_base + INTEL_ACTIVELTR);
>> +       writel(ltr, hba->mmio_base + INTEL_IDLELTR);
>> +
>> +       /* Cache the values into intel_host structure */
>> +       intel_cache_ltr(hba);
>> +out:
>> +       pm_runtime_put(dev);
>> +}
>> +
>> +static void ufs_intel_ltr_expose(struct ufs_hba *hba)
>> +{
>> +       struct intel_host *host = ufshcd_get_variant(hba);
>> +       struct dentry *dir = host->debugfs_root;
>> +       struct device *dev = hba->dev;
>> +
>> +       dev->power.set_latency_tolerance = intel_ltr_set;
>> +       dev_pm_qos_expose_latency_tolerance(dev);
>> +
>> +       intel_cache_ltr(hba);
>> +
>> +       debugfs_create_x32("active_ltr", 0444, dir, &host->active_ltr);
>> +       debugfs_create_x32("idle_ltr", 0444, dir, &host->idle_ltr);
> You might as well allow those values to be traced, e.g. use dev_pm_qos_update_user_latency_tolerance

The registers default to "no requirement" and there is no use-case for
reading the initial values, other than debugging for which there is debugfs.
 Add the fact that there are 2 registers, which should be the same, but what
if they are not, plus having to decode the register bits, doesn't seem worth it.

> 
>> +}
>> +
>> +static void ufs_intel_ltr_hide(struct ufs_hba *hba)
>> +{
>> +       struct device *dev = hba->dev;
>> +
>> +       dev_pm_qos_hide_latency_tolerance(dev);
>> +       dev->power.set_latency_tolerance = NULL;
>> +}
>> +
>> +static int ufs_intel_common_init(struct ufs_hba *hba)
>> +{
>> +       struct device *dev = hba->dev;
>> +       struct intel_host *host;
>> +
>> +       host = devm_kzalloc(dev, sizeof(*host), GFP_KERNEL);
>> +       if (!host)
>> +               return -ENOMEM;
>> +       ufshcd_set_variant(hba, host);
>> +       host->debugfs_root = debugfs_create_dir(dev_name(dev), NULL);
> Maybe pack the debugfs code together, i.e. move this just above debugfs_create_x32 ....

Yes, I can move all the debugfs code together.

> 
>> +       ufs_intel_ltr_expose(hba);
>> +       return 0;
>> +}
>> +
>> +static void ufs_intel_common_exit(struct ufs_hba *hba)
>> +{
>> +       struct intel_host *host = ufshcd_get_variant(hba);
>> +
>> +       debugfs_remove_recursive(host->debugfs_root);
>> +       ufs_intel_ltr_hide(hba);
>> +}
>> +
>>  static int ufs_intel_ehl_init(struct ufs_hba *hba)
>>  {
>>         hba->quirks |= UFSHCD_QUIRK_BROKEN_AUTO_HIBERN8;
>> -       return 0;
>> +       return ufs_intel_common_init(hba);
>>  }
>>
>>  static struct ufs_hba_variant_ops ufs_intel_cnl_hba_vops = {
>>         .name                   = "intel-pci",
>> +       .init                   = ufs_intel_common_init,
>> +       .exit                   = ufs_intel_common_exit,
>>         .link_startup_notify    = ufs_intel_link_startup_notify,
>>  };
>>
>>  static struct ufs_hba_variant_ops ufs_intel_ehl_hba_vops = {
>>         .name                   = "intel-pci",
>>         .init                   = ufs_intel_ehl_init,
>> +       .exit                   = ufs_intel_common_exit,
>>         .link_startup_notify    = ufs_intel_link_startup_notify,
>>  };
>>
>> @@ -162,6 +279,8 @@ ufshcd_pci_probe(struct pci_dev *pdev, const struct
>> pci_device_id *id)
>>                 return err;
>>         }
>>
>> +       pci_set_drvdata(pdev, hba);
>> +
>>         hba->vops = (struct ufs_hba_variant_ops *)id->driver_data;
>>
>>         err = ufshcd_init(hba, mmio_base, pdev->irq);
>> @@ -171,7 +290,6 @@ ufshcd_pci_probe(struct pci_dev *pdev, const struct
>> pci_device_id *id)
>>                 return err;
>>         }
>>
>> -       pci_set_drvdata(pdev, hba);
>>         pm_runtime_put_noidle(&pdev->dev);
>>         pm_runtime_allow(&pdev->dev);
>>
>> --
>> 2.17.1
>