Messages in this thread | | | Date | Wed, 3 Apr 2024 11:32:49 +0200 | Subject | Re: [PATCH v2] drm/ast: Fix soft lockup | From | Thomas Zimmermann <> |
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Am 03.04.24 um 11:02 schrieb Jammy Huang: > There is a while-loop in ast_dp_set_on_off() that could lead to > infinite-loop. This is because the register, VGACRI-Dx, checked in > this API is a scratch register actually controlled by a MCU, named > DPMCU, in BMC. > > These scratch registers are protected by scu-lock. If suc-lock is not > off, DPMCU can not update these registers and then host will have soft > lockup due to never updated status. > > DPMCU is used to control DP and relative registers to handshake with > host's VGA driver. Even the most time-consuming task, DP's link > training, is less than 100ms. 200ms should be enough. > > Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com> > Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
> --- > drivers/gpu/drm/ast/ast_dp.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/gpu/drm/ast/ast_dp.c b/drivers/gpu/drm/ast/ast_dp.c > index ebb6d8ebd44e..1e9259416980 100644 > --- a/drivers/gpu/drm/ast/ast_dp.c > +++ b/drivers/gpu/drm/ast/ast_dp.c > @@ -180,6 +180,7 @@ void ast_dp_set_on_off(struct drm_device *dev, bool on) > { > struct ast_device *ast = to_ast_device(dev); > u8 video_on_off = on; > + u32 i = 0; > > // Video On/Off > ast_set_index_reg_mask(ast, AST_IO_VGACRI, 0xE3, (u8) ~AST_DP_VIDEO_ENABLE, on); > @@ -192,6 +193,8 @@ void ast_dp_set_on_off(struct drm_device *dev, bool on) > ASTDP_MIRROR_VIDEO_ENABLE) != video_on_off) { > // wait 1 ms > mdelay(1); > + if (++i > 200) > + break; > } > } > } > > base-commit: b0546776ad3f332e215cebc0b063ba4351971cca
-- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)
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