Re: [PATCH v2 2/4] firmware: scm: Modify only the DLOAD bit in TCSR register for download mode

[Mukesh Ojha]

On 3/8/2023 8:36 PM, Srinivas Kandagatla wrote:
> On 01/03/2023 09:55, Mukesh Ojha wrote:
> > CrashDump collection is based on the DLOAD bit of TCSR register.
> > To retain other bits, we read the register and modify only the
> > DLOAD bit as the other bits have their own significance.
> >
> > Originally-by: Poovendhan Selvaraj <quic_poovendh@xxxxxxxxxxx>
> > Signed-off-by: Mukesh Ojha <quic_mojha@xxxxxxxxxxx>
> > ---
> > Changes in v2:
> >   - Addressed comment made by Bjorn.
> >   - Added download mask from patch 3 to this.
> >
> >   drivers/firmware/qcom_scm.c | 17 +++++++++++++++--
> >   1 file changed, 15 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
> > index 51eb853..c9f1fad 100644
> > --- a/drivers/firmware/qcom_scm.c
> > +++ b/drivers/firmware/qcom_scm.c
> > @@ -27,6 +27,8 @@ module_param(download_mode, bool, 0);
> >   #define SCM_HAS_IFACE_CLK    BIT(1)
> >   #define SCM_HAS_BUS_CLK        BIT(2)
> > +#define QCOM_DOWNLOAD_MODE_MASK 0x30
> > +
> >   struct qcom_scm {
> >       struct device *dev;
> >       struct clk *core_clk;
> > @@ -419,6 +421,7 @@ static void qcom_scm_set_download_mode(bool enable)
> >   {
> >       bool avail;
> >       int ret = 0;
> > +    u32 val;
> >       avail = __qcom_scm_is_call_available(__scm->dev,
> >                            QCOM_SCM_SVC_BOOT,
> > @@ -426,8 +429,18 @@ static void qcom_scm_set_download_mode(bool enable)
> >       if (avail) {
> >           ret = __qcom_scm_set_dload_mode(__scm->dev, enable);
> >       } else if (__scm->dload_mode_addr) {
> > -        ret = qcom_scm_io_writel(__scm->dload_mode_addr,
> > -                enable ? QCOM_SCM_BOOT_SET_DLOAD_MODE : 0);
> > +        ret = qcom_scm_io_readl(__scm->dload_mode_addr, &val);
> > +        if (ret) {
> > +            dev_err(__scm->dev,
> > +                "failed to read dload mode address value: %d\n", ret);
> > +            return;
> > +        }
> > +
> > +        val &= ~QCOM_DOWNLOAD_MODE_MASK;
> > +        if (enable)
> > +            val |= QCOM_SCM_BOOT_SET_DLOAD_MODE;
> > +
> > +        ret = qcom_scm_io_writel(__scm->dload_mode_addr, val);
>
>
> This is the second instance of such pattern of usage one is already in 
> ./drivers/pinctrl/qcom/pinctrl-msm.c
>
> I think it makes sense to move setting fields in register to a dedicated 
> function like this:
>
> int qcom_scm_io_update_field(phys_addr_t addr, unsigned int mask, 
> unsigned int val)
> {
>      unsigned int old, new;
>      int ret;
>
>      ret = qcom_scm_io_readl(addr, &old);
>      if (ret)
>          return ret;
>
>      new = (old & ~mask) | (val << ffs(mask) - 1);
>
>      return qcom_scm_io_writel(addr, new);
> }
> EXPORT_SYMBOL(qcom_scm_io_update_field);
>
>
> then we could use it like this:
> ret = qcom_scm_io_update_field(__scm->dload_mode_addr, 
> QCOM_DOWNLOAD_MODE_MASK, dl_mode)

Thanks for the review,

will do it in v2, will let /drivers/pinctrl/qcom/pinctrl-msm.c uses this.

-Mukesh
> --srini
> >       } else {
> >           dev_err(__scm->dev,
> >               "No available mechanism for setting download mode\n");