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    SubjectRe: [RFC v2 1/5] drm/mediatek: rename macros, add chip suffix
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    Hi Thierry,

    On Mon, 2016-05-30 at 12:41 +0200, Thierry Reding wrote:
    > On Fri, May 20, 2016 at 11:05:32PM +0800, yt.shen@mediatek.com wrote:
    > > From: YT Shen <yt.shen@mediatek.com>
    > >
    > > Add MT8173 suffix for hardware related macros.
    > >
    > > Signed-off-by: YT Shen <yt.shen@mediatek.com>
    > > ---
    > > drivers/gpu/drm/mediatek/mtk_drm_ddp.c | 62 ++++++++++++++++----------------
    > > 1 file changed, 31 insertions(+), 31 deletions(-)
    > >
    > > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp.c b/drivers/gpu/drm/mediatek/mtk_drm_ddp.c
    > > index 17ba935..d6aafd4 100644
    > > --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp.c
    > > +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp.c
    > > @@ -36,21 +36,21 @@
    > > #define DISP_REG_MUTEX_MOD(n) (0x2c + 0x20 * (n))
    > > #define DISP_REG_MUTEX_SOF(n) (0x30 + 0x20 * (n))
    > >
    > > -#define MUTEX_MOD_DISP_OVL0 BIT(11)
    > > -#define MUTEX_MOD_DISP_OVL1 BIT(12)
    > > -#define MUTEX_MOD_DISP_RDMA0 BIT(13)
    > > -#define MUTEX_MOD_DISP_RDMA1 BIT(14)
    > > -#define MUTEX_MOD_DISP_RDMA2 BIT(15)
    > > -#define MUTEX_MOD_DISP_WDMA0 BIT(16)
    > > -#define MUTEX_MOD_DISP_WDMA1 BIT(17)
    > > -#define MUTEX_MOD_DISP_COLOR0 BIT(18)
    > > -#define MUTEX_MOD_DISP_COLOR1 BIT(19)
    > > -#define MUTEX_MOD_DISP_AAL BIT(20)
    > > -#define MUTEX_MOD_DISP_GAMMA BIT(21)
    > > -#define MUTEX_MOD_DISP_UFOE BIT(22)
    > > -#define MUTEX_MOD_DISP_PWM0 BIT(23)
    > > -#define MUTEX_MOD_DISP_PWM1 BIT(24)
    > > -#define MUTEX_MOD_DISP_OD BIT(25)
    > > +#define MUTEX_MOD_DISP_OVL0_MT8173 BIT(11)
    > > +#define MUTEX_MOD_DISP_OVL1_MT8173 BIT(12)
    > > +#define MUTEX_MOD_DISP_RDMA0_MT8173 BIT(13)
    > > +#define MUTEX_MOD_DISP_RDMA1_MT8173 BIT(14)
    > > +#define MUTEX_MOD_DISP_RDMA2_MT8173 BIT(15)
    > > +#define MUTEX_MOD_DISP_WDMA0_MT8173 BIT(16)
    > > +#define MUTEX_MOD_DISP_WDMA1_MT8173 BIT(17)
    > > +#define MUTEX_MOD_DISP_COLOR0_MT8173 BIT(18)
    > > +#define MUTEX_MOD_DISP_COLOR1_MT8173 BIT(19)
    > > +#define MUTEX_MOD_DISP_AAL_MT8173 BIT(20)
    > > +#define MUTEX_MOD_DISP_GAMMA_MT8173 BIT(21)
    > > +#define MUTEX_MOD_DISP_UFOE_MT8173 BIT(22)
    > > +#define MUTEX_MOD_DISP_PWM0_MT8173 BIT(23)
    > > +#define MUTEX_MOD_DISP_PWM1_MT8173 BIT(24)
    > > +#define MUTEX_MOD_DISP_OD_MT8173 BIT(25)
    >
    > Just a random fly-by comment: this looks like a hardware spinlock, have
    > you ever considered implementing this as a hwspinlock driver? See the
    > drivers/hwspinlock subdirectory for existing examples.
    >
    > Thierry

    I see the drivers/hwspinlock and Documentation/hwspinlock.txt
    Yes, we can implement this like a hardware spinlock. But I have some
    questions, the document says:

    "Hardware spinlock modules provide hardware assistance for
    synchronization and mutual exclusion between heterogeneous processors
    and those not operating under a single, shared operating system"

    The mutex here is a handshake interface between software and hardware.
    The hardware is the display controller, the software is the drm display
    driver, and no other consumers need to access this mutex. So I think
    that using hwspinlock to implement a bit too complicated, am I right?

    I will use iopoll macros to implement this part in the next version.
    Thanks.

    yt.shen



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